﻿<?xml version="1.0" encoding="utf-8"?>
<Return xmlns="http://www.irs.gov/efile" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.irs.gov/efile" returnVersion="2018v3.1">
  <ReturnHeader binaryAttachmentCnt="0">
    <ReturnTs>2019-11-04T14:30:36-06:00</ReturnTs>
    <TaxPeriodEndDt>2018-12-31</TaxPeriodEndDt>
    <PreparerFirmGrp>
      <PreparerFirmEIN>111986323</PreparerFirmEIN>
      <PreparerFirmName>
        <BusinessNameLine1Txt>MARCUM LLP</BusinessNameLine1Txt>
      </PreparerFirmName>
      <PreparerUSAddress>
        <AddressLine1Txt>1899 L STREET NW SUITE 850</AddressLine1Txt>
        <CityNm>WASHINGTON</CityNm>
        <StateAbbreviationCd>DC</StateAbbreviationCd>
        <ZIPCd>20036</ZIPCd>
      </PreparerUSAddress>
    </PreparerFirmGrp>
    <ReturnTypeCd>990</ReturnTypeCd>
    <TaxPeriodBeginDt>2018-01-01</TaxPeriodBeginDt>
    <Filer>
      <EIN>510178702</EIN>
      <BusinessName>
        <BusinessNameLine1Txt>RADIATION ONCOLOGY INSTITUTE</BusinessNameLine1Txt>
      </BusinessName>
      <BusinessNameControlTxt>RADI</BusinessNameControlTxt>
      <PhoneNum>7035021550</PhoneNum>
      <USAddress>
        <AddressLine1Txt>251 18TH ST SOUTH 8TH FLOOR</AddressLine1Txt>
        <CityNm>ARLINGTON</CityNm>
        <StateAbbreviationCd>VA</StateAbbreviationCd>
        <ZIPCd>22202</ZIPCd>
      </USAddress>
    </Filer>
    <BusinessOfficerGrp>
      <PersonNm>LAURA I THEVENOT</PersonNm>
      <PersonTitleTxt>EX-OFFICIO, EXECUTIVE DIRECTOR</PersonTitleTxt>
      <PhoneNum>7035021550</PhoneNum>
      <SignatureDt>2019-11-04</SignatureDt>
      <DiscussWithPaidPreparerInd>1</DiscussWithPaidPreparerInd>
    </BusinessOfficerGrp>
    <PreparerPersonGrp>
      <PreparerPersonNm>FRANK H SMITH</PreparerPersonNm>
      <PTIN>P00639053</PTIN>
      <PhoneNum>2022274000</PhoneNum>
      <PreparationDt>2019-11-04</PreparationDt>
    </PreparerPersonGrp>
    <FilingSecurityInformation>
      <IPAddress>
        <IPv4AddressTxt>47.19.127.190</IPv4AddressTxt>
      </IPAddress>
      <IPDt>2019-11-04</IPDt>
      <IPTm>14:30:33</IPTm>
      <IPTimezoneCd>ES</IPTimezoneCd>
      <FilingLicenseTypeCd>P</FilingLicenseTypeCd>
      <AtSubmissionCreationDeviceId>DA39A3EE5E6B4B0D3255BFEF95601890AFD80709</AtSubmissionCreationDeviceId>
      <AtSubmissionFilingDeviceId>5A5EF588F1FD1486F2A951F54772A5295840024A</AtSubmissionFilingDeviceId>
    </FilingSecurityInformation>
    <TaxYr>2018</TaxYr>
    <BuildTS>2020-04-17 16:48:07Z</BuildTS>
  </ReturnHeader>
  <ReturnData documentCnt="8">
    <IRS990 documentId="RetDoc1038000001" referenceDocumentId="RetDoc1044400001">
      <PrincipalOfficerNm>LAURA I THEVENOT</PrincipalOfficerNm>
      <USAddress>
        <AddressLine1Txt>251 18TH ST SOUTH 8TH FLOOR</AddressLine1Txt>
        <CityNm>ARLINGTON</CityNm>
        <StateAbbreviationCd>VA</StateAbbreviationCd>
        <ZIPCd>22202</ZIPCd>
      </USAddress>
      <GrossReceiptsAmt>4548581</GrossReceiptsAmt>
      <GroupReturnForAffiliatesInd>0</GroupReturnForAffiliatesInd>
      <Organization501c3Ind>X</Organization501c3Ind>
      <WebsiteAddressTxt>WWW.ROINSTITUTE.ORG</WebsiteAddressTxt>
      <TypeOfOrganizationCorpInd>X</TypeOfOrganizationCorpInd>
      <FormationYr>1978</FormationYr>
      <LegalDomicileStateCd>IL</LegalDomicileStateCd>
      <ActivityOrMissionDesc>TO ENHANCE AND PROMOTE THE CRITICAL ROLE OF RADIATION THERAPY IN THE TREATMENT OF CANCER.</ActivityOrMissionDesc>
      <VotingMembersGoverningBodyCnt>11</VotingMembersGoverningBodyCnt>
      <VotingMembersIndependentCnt>11</VotingMembersIndependentCnt>
      <TotalEmployeeCnt>0</TotalEmployeeCnt>
      <TotalVolunteersCnt>52</TotalVolunteersCnt>
      <TotalGrossUBIAmt>0</TotalGrossUBIAmt>
      <NetUnrelatedBusTxblIncmAmt>0</NetUnrelatedBusTxblIncmAmt>
      <PYContributionsGrantsAmt>451618</PYContributionsGrantsAmt>
      <CYContributionsGrantsAmt>662029</CYContributionsGrantsAmt>
      <PYProgramServiceRevenueAmt>0</PYProgramServiceRevenueAmt>
      <CYProgramServiceRevenueAmt>0</CYProgramServiceRevenueAmt>
      <PYInvestmentIncomeAmt>710540</PYInvestmentIncomeAmt>
      <CYInvestmentIncomeAmt>617074</CYInvestmentIncomeAmt>
      <PYOtherRevenueAmt>0</PYOtherRevenueAmt>
      <CYOtherRevenueAmt>2205</CYOtherRevenueAmt>
      <PYTotalRevenueAmt>1162158</PYTotalRevenueAmt>
      <CYTotalRevenueAmt>1281308</CYTotalRevenueAmt>
      <PYGrantsAndSimilarPaidAmt>215687</PYGrantsAndSimilarPaidAmt>
      <CYGrantsAndSimilarPaidAmt>256039</CYGrantsAndSimilarPaidAmt>
      <PYBenefitsPaidToMembersAmt>0</PYBenefitsPaidToMembersAmt>
      <CYBenefitsPaidToMembersAmt>0</CYBenefitsPaidToMembersAmt>
      <PYSalariesCompEmpBnftPaidAmt>201950</PYSalariesCompEmpBnftPaidAmt>
      <CYSalariesCompEmpBnftPaidAmt>291265</CYSalariesCompEmpBnftPaidAmt>
      <PYTotalProfFndrsngExpnsAmt>0</PYTotalProfFndrsngExpnsAmt>
      <CYTotalProfFndrsngExpnsAmt>0</CYTotalProfFndrsngExpnsAmt>
      <CYTotalFundraisingExpenseAmt>309673</CYTotalFundraisingExpenseAmt>
      <PYOtherExpensesAmt>239626</PYOtherExpensesAmt>
      <CYOtherExpensesAmt>322286</CYOtherExpensesAmt>
      <PYTotalExpensesAmt>657263</PYTotalExpensesAmt>
      <CYTotalExpensesAmt>869590</CYTotalExpensesAmt>
      <PYRevenuesLessExpensesAmt>504895</PYRevenuesLessExpensesAmt>
      <CYRevenuesLessExpensesAmt>411718</CYRevenuesLessExpensesAmt>
      <TotalAssetsBOYAmt>13299739</TotalAssetsBOYAmt>
      <TotalAssetsEOYAmt>12223111</TotalAssetsEOYAmt>
      <TotalLiabilitiesBOYAmt>12606</TotalLiabilitiesBOYAmt>
      <TotalLiabilitiesEOYAmt>35936</TotalLiabilitiesEOYAmt>
      <NetAssetsOrFundBalancesBOYAmt>13287133</NetAssetsOrFundBalancesBOYAmt>
      <NetAssetsOrFundBalancesEOYAmt>12187175</NetAssetsOrFundBalancesEOYAmt>
      <InfoInScheduleOPartIIIInd>X</InfoInScheduleOPartIIIInd>
      <MissionDesc>THE RADIATION ONCOLOGY INSTITUTE (ROI) WILL ENHANCE AND PROMOTE THE CRITICAL ROLE OF RADIATION THERAPY IN THE TREATMENT OF CANCER BY SUPPORTING RESEARCH AND EDUCATION ABOUT THE LIVE-SAVING AND QUALITY-OF-LIFE BENEFITS OF RADIATION THERAPY.</MissionDesc>
      <SignificantNewProgramSrvcInd>0</SignificantNewProgramSrvcInd>
      <SignificantChangeInd>0</SignificantChangeInd>
      <ExpenseAmt>186301</ExpenseAmt>
      <GrantAmt>151536</GrantAmt>
      <RevenueAmt>2205</RevenueAmt>
      <Desc>TOXICITY MANAGEMENT PROJECT - DEALS WITH THE MANAGEMENT AND ON-GOING FOLLOW-UP OF ADVERSE EFFECTS RELATED TO RADIATION THERAPY. THE RADONC TOOLBOX APP AND WEBSITE WILL IMPROVE COMMUNICATION AND KNOWLEDGE AMONG NON-RADIATION THERAPY HEALTH CARE PROVIDERS IN ORDER TO IMPROVE PATIENT OUTCOMES AND QUALITY OF LIFE METRICS. A RESEARCH PROJECT USING ACTIVITY TRACKERS IS TESTING WHETHER A SIMPLE WALKING PROGRAM COULD LESSEN TREATMENT-RELATED TOXICITIES AND IMPROVE PATIENT QUALITY OF LIFE.</Desc>
      <ProgSrvcAccomActy2Grp>
        <ExpenseAmt>77490</ExpenseAmt>
        <GrantAmt>75000</GrantAmt>
        <Desc>SAFETY AND QUALITY - THE BIG DATA PROJECT PROVIDES NEW OPPORTUNITIES TO IMPROVE QUALITY ASSURANCE AND QUALITY IMPROVEMENT EFFORTS BY MAKING IT POSSIBLE TO TARGET AND BETTER FOCUS RESOURCES WHERE THEY ARE MOST NEEDED. CURRENT QUALITY ASSURANCE METHODS OFTEN TAKE A UNIFORM APPROACH, TREATING EVERY PATIENT CASE IN A BROAD CATEGORY WITH THE SAME PROCESS AND INTENSITY OF EXAMINATION. THIS PROGRAM SEEKS TO LEVERAGE BIG DATA TO OPTIMIZE QUALITY ASSURANCE AND PATIENT CARE IMPROVEMENTS INITIATIVES.</Desc>
      </ProgSrvcAccomActy2Grp>
      <ProgSrvcAccomActy3Grp>
        <ExpenseAmt>15881</ExpenseAmt>
        <GrantAmt>14503</GrantAmt>
        <Desc>DECISION MAKING PROJECT - THE RADIATION ONCOLOGY INSTITUTE SUPPORTS RESEARCH TO ENSURE THAT CANCER PATIENTS UNDERSTAND ALL THEIR TREATMENT OPTIONS, INCLUDING RADIATION THERAPY, AND THAT THEY HAVE ACCESS TO THE CONTINUUM OF CARE THEY NEED.</Desc>
      </ProgSrvcAccomActy3Grp>
      <ProgSrvcAccomActyOtherGrp>
        <ExpenseAmt>24862</ExpenseAmt>
        <GrantAmt>15000</GrantAmt>
        <Desc>RESEARCH COMMITTEE</Desc>
      </ProgSrvcAccomActyOtherGrp>
      <ProgSrvcAccomActyOtherGrp>
        <ExpenseAmt>10379</ExpenseAmt>
        <Desc>DEL REGATO</Desc>
      </ProgSrvcAccomActyOtherGrp>
      <ProgSrvcAccomActyOtherGrp>
        <ExpenseAmt>7107</ExpenseAmt>
        <Desc>PUBLICATION AWARD</Desc>
      </ProgSrvcAccomActyOtherGrp>
      <ProgSrvcAccomActyOtherGrp>
        <ExpenseAmt>2260</ExpenseAmt>
        <Desc>VALUE OF RADIATION THERAPY</Desc>
      </ProgSrvcAccomActyOtherGrp>
      <TotalOtherProgSrvcExpenseAmt>44608</TotalOtherProgSrvcExpenseAmt>
      <TotalOtherProgSrvcGrantAmt>15000</TotalOtherProgSrvcGrantAmt>
      <TotalProgramServiceExpensesAmt>324280</TotalProgramServiceExpensesAmt>
      <DescribedInSection501c3Ind referenceDocumentId="RetDoc1039100001">1</DescribedInSection501c3Ind>
      <ScheduleBRequiredInd referenceDocumentId="RetDoc1234500001">1</ScheduleBRequiredInd>
      <PoliticalCampaignActyInd>0</PoliticalCampaignActyInd>
      <LobbyingActivitiesInd>0</LobbyingActivitiesInd>
      <SubjectToProxyTaxInd>0</SubjectToProxyTaxInd>
      <DonorAdvisedFundInd referenceDocumentId="RetDoc1040000001">0</DonorAdvisedFundInd>
      <ConservationEasementsInd referenceDocumentId="RetDoc1040000001">0</ConservationEasementsInd>
      <CollectionsOfArtInd referenceDocumentId="RetDoc1040000001">0</CollectionsOfArtInd>
      <CreditCounselingInd referenceDocumentId="RetDoc1040000001">0</CreditCounselingInd>
      <TempOrPermanentEndowmentsInd referenceDocumentId="RetDoc1040000001">1</TempOrPermanentEndowmentsInd>
      <ReportLandBuildingEquipmentInd referenceDocumentId="RetDoc1040000001">0</ReportLandBuildingEquipmentInd>
      <ReportInvestmentsOtherSecInd referenceDocumentId="RetDoc1040000001">0</ReportInvestmentsOtherSecInd>
      <ReportProgramRelatedInvstInd referenceDocumentId="RetDoc1040000001">0</ReportProgramRelatedInvstInd>
      <ReportOtherAssetsInd referenceDocumentId="RetDoc1040000001">0</ReportOtherAssetsInd>
      <ReportOtherLiabilitiesInd referenceDocumentId="RetDoc1040000001">0</ReportOtherLiabilitiesInd>
      <IncludeFIN48FootnoteInd referenceDocumentId="RetDoc1040000001">1</IncludeFIN48FootnoteInd>
      <IndependentAuditFinclStmtInd referenceDocumentId="RetDoc1040000001">1</IndependentAuditFinclStmtInd>
      <ConsolidatedAuditFinclStmtInd referenceDocumentId="RetDoc1040000001">1</ConsolidatedAuditFinclStmtInd>
      <SchoolOperatingInd>0</SchoolOperatingInd>
      <ForeignOfficeInd>0</ForeignOfficeInd>
      <ForeignActivitiesInd>0</ForeignActivitiesInd>
      <MoreThan5000KToOrgInd>0</MoreThan5000KToOrgInd>
      <MoreThan5000KToIndividualsInd>0</MoreThan5000KToIndividualsInd>
      <ProfessionalFundraisingInd>0</ProfessionalFundraisingInd>
      <FundraisingActivitiesInd>0</FundraisingActivitiesInd>
      <GamingActivitiesInd>0</GamingActivitiesInd>
      <OperateHospitalInd>0</OperateHospitalInd>
      <GrantsToOrganizationsInd referenceDocumentId="RetDoc1041900001">1</GrantsToOrganizationsInd>
      <GrantsToIndividualsInd referenceDocumentId="RetDoc1041900001">0</GrantsToIndividualsInd>
      <ScheduleJRequiredInd referenceDocumentId="RetDoc1042400001">1</ScheduleJRequiredInd>
      <TaxExemptBondsInd>0</TaxExemptBondsInd>
      <EngagedInExcessBenefitTransInd>0</EngagedInExcessBenefitTransInd>
      <PYExcessBenefitTransInd>0</PYExcessBenefitTransInd>
      <LoanOutstandingInd>0</LoanOutstandingInd>
      <GrantToRelatedPersonInd>0</GrantToRelatedPersonInd>
      <BusinessRlnWithOrgMemInd>0</BusinessRlnWithOrgMemInd>
      <BusinessRlnWithFamMemInd>0</BusinessRlnWithFamMemInd>
      <BusinessRlnWithOfficerEntInd>0</BusinessRlnWithOfficerEntInd>
      <DeductibleNonCashContriInd>0</DeductibleNonCashContriInd>
      <DeductibleArtContributionInd>0</DeductibleArtContributionInd>
      <TerminateOperationsInd>0</TerminateOperationsInd>
      <PartialLiquidationInd>0</PartialLiquidationInd>
      <DisregardedEntityInd referenceDocumentId="RetDoc1043400001">0</DisregardedEntityInd>
      <RelatedEntityInd referenceDocumentId="RetDoc1043400001">1</RelatedEntityInd>
      <RelatedOrganizationCtrlEntInd>0</RelatedOrganizationCtrlEntInd>
      <TrnsfrExmptNonChrtblRltdOrgInd referenceDocumentId="RetDoc1043400001">1</TrnsfrExmptNonChrtblRltdOrgInd>
      <ActivitiesConductedPrtshpInd referenceDocumentId="RetDoc1043400001">0</ActivitiesConductedPrtshpInd>
      <ScheduleORequiredInd>1</ScheduleORequiredInd>
      <IRPDocumentCnt>2</IRPDocumentCnt>
      <IRPDocumentW2GCnt>0</IRPDocumentW2GCnt>
      <BackupWthldComplianceInd>1</BackupWthldComplianceInd>
      <EmployeeCnt>0</EmployeeCnt>
      <UnrelatedBusIncmOverLimitInd>0</UnrelatedBusIncmOverLimitInd>
      <ForeignFinancialAccountInd>0</ForeignFinancialAccountInd>
      <ProhibitedTaxShelterTransInd>0</ProhibitedTaxShelterTransInd>
      <TaxablePartyNotificationInd>0</TaxablePartyNotificationInd>
      <NondeductibleContributionsInd>0</NondeductibleContributionsInd>
      <QuidProQuoContributionsInd>0</QuidProQuoContributionsInd>
      <Form8282PropertyDisposedOfInd>0</Form8282PropertyDisposedOfInd>
      <RcvFndsToPayPrsnlBnftCntrctInd>0</RcvFndsToPayPrsnlBnftCntrctInd>
      <PayPremiumsPrsnlBnftCntrctInd>0</PayPremiumsPrsnlBnftCntrctInd>
      <IndoorTanningServicesInd>0</IndoorTanningServicesInd>
      <SubjToTaxRmnrtnExPrchtPymtInd>0</SubjToTaxRmnrtnExPrchtPymtInd>
      <SubjectToExcsTaxNetInvstIncInd>0</SubjectToExcsTaxNetInvstIncInd>
      <InfoInScheduleOPartVIInd>X</InfoInScheduleOPartVIInd>
      <GoverningBodyVotingMembersCnt>11</GoverningBodyVotingMembersCnt>
      <IndependentVotingMemberCnt>11</IndependentVotingMemberCnt>
      <FamilyOrBusinessRlnInd>0</FamilyOrBusinessRlnInd>
      <DelegationOfMgmtDutiesInd>1</DelegationOfMgmtDutiesInd>
      <ChangeToOrgDocumentsInd>0</ChangeToOrgDocumentsInd>
      <MaterialDiversionOrMisuseInd>0</MaterialDiversionOrMisuseInd>
      <MembersOrStockholdersInd>0</MembersOrStockholdersInd>
      <ElectionOfBoardMembersInd>0</ElectionOfBoardMembersInd>
      <DecisionsSubjectToApprovaInd>0</DecisionsSubjectToApprovaInd>
      <MinutesOfGoverningBodyInd>1</MinutesOfGoverningBodyInd>
      <MinutesOfCommitteesInd>1</MinutesOfCommitteesInd>
      <OfficerMailingAddressInd>0</OfficerMailingAddressInd>
      <LocalChaptersInd>0</LocalChaptersInd>
      <Form990ProvidedToGvrnBodyInd>1</Form990ProvidedToGvrnBodyInd>
      <ConflictOfInterestPolicyInd>1</ConflictOfInterestPolicyInd>
      <AnnualDisclosureCoveredPrsnInd>1</AnnualDisclosureCoveredPrsnInd>
      <RegularMonitoringEnfrcInd>1</RegularMonitoringEnfrcInd>
      <WhistleblowerPolicyInd>1</WhistleblowerPolicyInd>
      <DocumentRetentionPolicyInd>1</DocumentRetentionPolicyInd>
      <CompensationProcessCEOInd>0</CompensationProcessCEOInd>
      <CompensationProcessOtherInd>0</CompensationProcessOtherInd>
      <InvestmentInJointVentureInd>0</InvestmentInJointVentureInd>
      <StatesWhereCopyOfReturnIsFldCd>IL</StatesWhereCopyOfReturnIsFldCd>
      <StatesWhereCopyOfReturnIsFldCd>VA</StatesWhereCopyOfReturnIsFldCd>
      <UponRequestInd>X</UponRequestInd>
      <BooksInCareOfDetail>
        <BusinessName>
          <BusinessNameLine1Txt>PATRICIA B LAWLOR</BusinessNameLine1Txt>
        </BusinessName>
        <PhoneNum>7035021550</PhoneNum>
        <USAddress>
          <AddressLine1Txt>251 18TH ST SOUTH 8TH FLOOR</AddressLine1Txt>
          <CityNm>ARLINGTON</CityNm>
          <StateAbbreviationCd>VA</StateAbbreviationCd>
          <ZIPCd>22202</ZIPCd>
        </USAddress>
      </BooksInCareOfDetail>
      <Form990PartVIISectionAGrp>
        <PersonNm>DEBORAH A KUBAN</PersonNm>
        <TitleTxt>PRESIDENT</TitleTxt>
        <AverageHoursPerWeekRt>1.00</AverageHoursPerWeekRt>
        <IndividualTrusteeOrDirectorInd>X</IndividualTrusteeOrDirectorInd>
        <OfficerInd>X</OfficerInd>
        <ReportableCompFromOrgAmt>0</ReportableCompFromOrgAmt>
        <ReportableCompFromRltdOrgAmt>0</ReportableCompFromRltdOrgAmt>
        <OtherCompensationAmt>0</OtherCompensationAmt>
      </Form990PartVIISectionAGrp>
      <Form990PartVIISectionAGrp>
        <PersonNm>COLLEEN A F LAWTON</PersonNm>
        <TitleTxt>VICE PRESIDENT</TitleTxt>
        <AverageHoursPerWeekRt>1.00</AverageHoursPerWeekRt>
        <IndividualTrusteeOrDirectorInd>X</IndividualTrusteeOrDirectorInd>
        <OfficerInd>X</OfficerInd>
        <ReportableCompFromOrgAmt>0</ReportableCompFromOrgAmt>
        <ReportableCompFromRltdOrgAmt>0</ReportableCompFromRltdOrgAmt>
        <OtherCompensationAmt>0</OtherCompensationAmt>
      </Form990PartVIISectionAGrp>
      <Form990PartVIISectionAGrp>
        <PersonNm>TIMOTHY E GUERTIN PUBLIC</PersonNm>
        <TitleTxt>TRUSTEE AND TREASUR.-UNTIL 10/2018</TitleTxt>
        <AverageHoursPerWeekRt>1.00</AverageHoursPerWeekRt>
        <IndividualTrusteeOrDirectorInd>X</IndividualTrusteeOrDirectorInd>
        <OfficerInd>X</OfficerInd>
        <ReportableCompFromOrgAmt>0</ReportableCompFromOrgAmt>
        <ReportableCompFromRltdOrgAmt>0</ReportableCompFromRltdOrgAmt>
        <OtherCompensationAmt>0</OtherCompensationAmt>
      </Form990PartVIISectionAGrp>
      <Form990PartVIISectionAGrp>
        <PersonNm>THEODORE S LAWRENCE</PersonNm>
        <TitleTxt>IMMEDIATE PAST PRESIDENT</TitleTxt>
        <AverageHoursPerWeekRt>1.00</AverageHoursPerWeekRt>
        <IndividualTrusteeOrDirectorInd>X</IndividualTrusteeOrDirectorInd>
        <OfficerInd>X</OfficerInd>
        <ReportableCompFromOrgAmt>0</ReportableCompFromOrgAmt>
        <ReportableCompFromRltdOrgAmt>0</ReportableCompFromRltdOrgAmt>
        <OtherCompensationAmt>0</OtherCompensationAmt>
      </Form990PartVIISectionAGrp>
      <Form990PartVIISectionAGrp>
        <PersonNm>JAMES P HOEY</PersonNm>
        <TitleTxt>PUBLIC TRUSTEE</TitleTxt>
        <AverageHoursPerWeekRt>1.00</AverageHoursPerWeekRt>
        <IndividualTrusteeOrDirectorInd>X</IndividualTrusteeOrDirectorInd>
        <ReportableCompFromOrgAmt>0</ReportableCompFromOrgAmt>
        <ReportableCompFromRltdOrgAmt>0</ReportableCompFromRltdOrgAmt>
        <OtherCompensationAmt>0</OtherCompensationAmt>
      </Form990PartVIISectionAGrp>
      <Form990PartVIISectionAGrp>
        <PersonNm>JOSEPH K JACHINOWSKI</PersonNm>
        <TitleTxt>PUBLIC TRUSTEE</TitleTxt>
        <AverageHoursPerWeekRt>1.00</AverageHoursPerWeekRt>
        <IndividualTrusteeOrDirectorInd>X</IndividualTrusteeOrDirectorInd>
        <ReportableCompFromOrgAmt>0</ReportableCompFromOrgAmt>
        <ReportableCompFromRltdOrgAmt>0</ReportableCompFromRltdOrgAmt>
        <OtherCompensationAmt>0</OtherCompensationAmt>
      </Form990PartVIISectionAGrp>
      <Form990PartVIISectionAGrp>
        <PersonNm>KOLLEEN T KENNEDY</PersonNm>
        <TitleTxt>PUBLIC TRUSTEE</TitleTxt>
        <AverageHoursPerWeekRt>1.00</AverageHoursPerWeekRt>
        <IndividualTrusteeOrDirectorInd>X</IndividualTrusteeOrDirectorInd>
        <ReportableCompFromOrgAmt>0</ReportableCompFromOrgAmt>
        <ReportableCompFromRltdOrgAmt>0</ReportableCompFromRltdOrgAmt>
        <OtherCompensationAmt>0</OtherCompensationAmt>
      </Form990PartVIISectionAGrp>
      <Form990PartVIISectionAGrp>
        <PersonNm>CHRISTOPHER M ROSE</PersonNm>
        <TitleTxt>TRUSTEE</TitleTxt>
        <AverageHoursPerWeekRt>1.00</AverageHoursPerWeekRt>
        <IndividualTrusteeOrDirectorInd>X</IndividualTrusteeOrDirectorInd>
        <ReportableCompFromOrgAmt>0</ReportableCompFromOrgAmt>
        <ReportableCompFromRltdOrgAmt>0</ReportableCompFromRltdOrgAmt>
        <OtherCompensationAmt>0</OtherCompensationAmt>
      </Form990PartVIISectionAGrp>
      <Form990PartVIISectionAGrp>
        <PersonNm>TIM WILLIAMS</PersonNm>
        <TitleTxt>TRUSTEE</TitleTxt>
        <AverageHoursPerWeekRt>1.00</AverageHoursPerWeekRt>
        <IndividualTrusteeOrDirectorInd>X</IndividualTrusteeOrDirectorInd>
        <ReportableCompFromOrgAmt>0</ReportableCompFromOrgAmt>
        <ReportableCompFromRltdOrgAmt>0</ReportableCompFromRltdOrgAmt>
        <OtherCompensationAmt>0</OtherCompensationAmt>
      </Form990PartVIISectionAGrp>
      <Form990PartVIISectionAGrp>
        <PersonNm>J FRANK WILSON</PersonNm>
        <TitleTxt>TRUSTEE</TitleTxt>
        <AverageHoursPerWeekRt>1.00</AverageHoursPerWeekRt>
        <IndividualTrusteeOrDirectorInd>X</IndividualTrusteeOrDirectorInd>
        <ReportableCompFromOrgAmt>0</ReportableCompFromOrgAmt>
        <ReportableCompFromRltdOrgAmt>0</ReportableCompFromRltdOrgAmt>
        <OtherCompensationAmt>0</OtherCompensationAmt>
      </Form990PartVIISectionAGrp>
      <Form990PartVIISectionAGrp>
        <PersonNm>DAVID C BEYER ASTRO</PersonNm>
        <TitleTxt>REPRESENTATION - UNTIL 10/2018</TitleTxt>
        <AverageHoursPerWeekRt>1.00</AverageHoursPerWeekRt>
        <AverageHoursPerWeekRltdOrgRt>2.00</AverageHoursPerWeekRltdOrgRt>
        <IndividualTrusteeOrDirectorInd>X</IndividualTrusteeOrDirectorInd>
        <ReportableCompFromOrgAmt>0</ReportableCompFromOrgAmt>
        <ReportableCompFromRltdOrgAmt>0</ReportableCompFromRltdOrgAmt>
        <OtherCompensationAmt>0</OtherCompensationAmt>
      </Form990PartVIISectionAGrp>
      <Form990PartVIISectionAGrp>
        <PersonNm>BRIAN D KAVANAGH</PersonNm>
        <TitleTxt>ASTRO REPRESENTATION</TitleTxt>
        <AverageHoursPerWeekRt>1.00</AverageHoursPerWeekRt>
        <AverageHoursPerWeekRltdOrgRt>2.00</AverageHoursPerWeekRltdOrgRt>
        <IndividualTrusteeOrDirectorInd>X</IndividualTrusteeOrDirectorInd>
        <ReportableCompFromOrgAmt>0</ReportableCompFromOrgAmt>
        <ReportableCompFromRltdOrgAmt>0</ReportableCompFromRltdOrgAmt>
        <OtherCompensationAmt>0</OtherCompensationAmt>
      </Form990PartVIISectionAGrp>
      <Form990PartVIISectionAGrp>
        <PersonNm>DANIEL LOW</PersonNm>
        <TitleTxt>ASTRO REPRESENTATION</TitleTxt>
        <AverageHoursPerWeekRt>1.00</AverageHoursPerWeekRt>
        <AverageHoursPerWeekRltdOrgRt>2.00</AverageHoursPerWeekRltdOrgRt>
        <IndividualTrusteeOrDirectorInd>X</IndividualTrusteeOrDirectorInd>
        <ReportableCompFromOrgAmt>0</ReportableCompFromOrgAmt>
        <ReportableCompFromRltdOrgAmt>0</ReportableCompFromRltdOrgAmt>
        <OtherCompensationAmt>0</OtherCompensationAmt>
      </Form990PartVIISectionAGrp>
      <Form990PartVIISectionAGrp>
        <PersonNm>LAURA I THEVENOT</PersonNm>
        <TitleTxt>EX-OFFICIO, EXECUTIVE DIRE</TitleTxt>
        <AverageHoursPerWeekRt>4.00</AverageHoursPerWeekRt>
        <AverageHoursPerWeekRltdOrgRt>36.00</AverageHoursPerWeekRltdOrgRt>
        <OfficerInd>X</OfficerInd>
        <ReportableCompFromOrgAmt>0</ReportableCompFromOrgAmt>
        <ReportableCompFromRltdOrgAmt>651553</ReportableCompFromRltdOrgAmt>
        <OtherCompensationAmt>77231</OtherCompensationAmt>
      </Form990PartVIISectionAGrp>
      <TotalReportableCompFromOrgAmt>0</TotalReportableCompFromOrgAmt>
      <TotReportableCompRltdOrgAmt>651553</TotReportableCompRltdOrgAmt>
      <TotalOtherCompensationAmt>77231</TotalOtherCompensationAmt>
      <IndivRcvdGreaterThan100KCnt>0</IndivRcvdGreaterThan100KCnt>
      <FormerOfcrEmployeesListedInd>0</FormerOfcrEmployeesListedInd>
      <TotalCompGreaterThan150KInd>1</TotalCompGreaterThan150KInd>
      <CompensationFromOtherSrcsInd>0</CompensationFromOtherSrcsInd>
      <CntrctRcvdGreaterThan100KCnt>0</CntrctRcvdGreaterThan100KCnt>
      <RelatedOrganizationsAmt>136653</RelatedOrganizationsAmt>
      <AllOtherContributionsAmt>525376</AllOtherContributionsAmt>
      <TotalContributionsAmt>662029</TotalContributionsAmt>
      <InvestmentIncomeGrp>
        <TotalRevenueColumnAmt>301742</TotalRevenueColumnAmt>
        <ExclusionAmt>301742</ExclusionAmt>
      </InvestmentIncomeGrp>
      <GrossAmountSalesAssetsGrp>
        <SecuritiesAmt>3582605</SecuritiesAmt>
      </GrossAmountSalesAssetsGrp>
      <LessCostOthBasisSalesExpnssGrp>
        <SecuritiesAmt>3267273</SecuritiesAmt>
      </LessCostOthBasisSalesExpnssGrp>
      <GainOrLossGrp>
        <SecuritiesAmt>315332</SecuritiesAmt>
      </GainOrLossGrp>
      <NetGainOrLossInvestmentsGrp>
        <TotalRevenueColumnAmt>315332</TotalRevenueColumnAmt>
        <ExclusionAmt>315332</ExclusionAmt>
      </NetGainOrLossInvestmentsGrp>
      <OtherRevenueMiscGrp>
        <Desc>REGISTRATION FEES</Desc>
        <BusinessCd>900099</BusinessCd>
        <TotalRevenueColumnAmt>2205</TotalRevenueColumnAmt>
        <ExclusionAmt>2205</ExclusionAmt>
      </OtherRevenueMiscGrp>
      <OtherRevenueTotalAmt>2205</OtherRevenueTotalAmt>
      <TotalRevenueGrp>
        <TotalRevenueColumnAmt>1281308</TotalRevenueColumnAmt>
        <RelatedOrExemptFuncIncomeAmt>0</RelatedOrExemptFuncIncomeAmt>
        <UnrelatedBusinessRevenueAmt>0</UnrelatedBusinessRevenueAmt>
        <ExclusionAmt>619279</ExclusionAmt>
      </TotalRevenueGrp>
      <GrantsToDomesticOrgsGrp>
        <TotalAmt>256039</TotalAmt>
        <ProgramServicesAmt>256039</ProgramServicesAmt>
      </GrantsToDomesticOrgsGrp>
      <OtherSalariesAndWagesGrp>
        <TotalAmt>291265</TotalAmt>
        <ProgramServicesAmt>42454</ProgramServicesAmt>
        <ManagementAndGeneralAmt>98430</ManagementAndGeneralAmt>
        <FundraisingAmt>150381</FundraisingAmt>
      </OtherSalariesAndWagesGrp>
      <FeesForServicesLegalGrp>
        <TotalAmt>2400</TotalAmt>
        <ProgramServicesAmt>405</ProgramServicesAmt>
        <ManagementAndGeneralAmt>1995</ManagementAndGeneralAmt>
      </FeesForServicesLegalGrp>
      <FeesForServicesAccountingGrp>
        <TotalAmt>15171</TotalAmt>
        <ManagementAndGeneralAmt>15171</ManagementAndGeneralAmt>
      </FeesForServicesAccountingGrp>
      <FeesForSrvcInvstMgmntFeesGrp>
        <TotalAmt>40530</TotalAmt>
        <ManagementAndGeneralAmt>40530</ManagementAndGeneralAmt>
      </FeesForSrvcInvstMgmntFeesGrp>
      <FeesForServicesOtherGrp>
        <TotalAmt>8831</TotalAmt>
        <ProgramServicesAmt>4631</ProgramServicesAmt>
        <FundraisingAmt>4200</FundraisingAmt>
      </FeesForServicesOtherGrp>
      <OfficeExpensesGrp>
        <TotalAmt>32105</TotalAmt>
        <ProgramServicesAmt>184</ProgramServicesAmt>
        <ManagementAndGeneralAmt>10600</ManagementAndGeneralAmt>
        <FundraisingAmt>21321</FundraisingAmt>
      </OfficeExpensesGrp>
      <InformationTechnologyGrp>
        <TotalAmt>587</TotalAmt>
        <ManagementAndGeneralAmt>587</ManagementAndGeneralAmt>
      </InformationTechnologyGrp>
      <OccupancyGrp>
        <TotalAmt>139739</TotalAmt>
        <ProgramServicesAmt>20368</ProgramServicesAmt>
        <ManagementAndGeneralAmt>47223</ManagementAndGeneralAmt>
        <FundraisingAmt>72148</FundraisingAmt>
      </OccupancyGrp>
      <TravelGrp>
        <TotalAmt>19920</TotalAmt>
        <ManagementAndGeneralAmt>15145</ManagementAndGeneralAmt>
        <FundraisingAmt>4775</FundraisingAmt>
      </TravelGrp>
      <ConferencesMeetingsGrp>
        <TotalAmt>27275</TotalAmt>
        <ManagementAndGeneralAmt>2981</ManagementAndGeneralAmt>
        <FundraisingAmt>24294</FundraisingAmt>
      </ConferencesMeetingsGrp>
      <InterestGrp>
        <TotalAmt>42</TotalAmt>
        <ManagementAndGeneralAmt>42</ManagementAndGeneralAmt>
      </InterestGrp>
      <InsuranceGrp>
        <TotalAmt>2405</TotalAmt>
        <ManagementAndGeneralAmt>2405</ManagementAndGeneralAmt>
      </InsuranceGrp>
      <OtherExpensesGrp>
        <Desc>BAD DEBT EXPENSE</Desc>
        <TotalAmt>21500</TotalAmt>
        <FundraisingAmt>21500</FundraisingAmt>
      </OtherExpensesGrp>
      <OtherExpensesGrp>
        <Desc>DUES AND PUBLICATIONS</Desc>
        <TotalAmt>11069</TotalAmt>
        <ProgramServicesAmt>105</ProgramServicesAmt>
        <ManagementAndGeneralAmt>528</ManagementAndGeneralAmt>
        <FundraisingAmt>10436</FundraisingAmt>
      </OtherExpensesGrp>
      <OtherExpensesGrp>
        <Desc>AWARDS &amp; GIFTS</Desc>
        <TotalAmt>637</TotalAmt>
        <ProgramServicesAmt>94</ProgramServicesAmt>
        <FundraisingAmt>543</FundraisingAmt>
      </OtherExpensesGrp>
      <OtherExpensesGrp>
        <Desc>STAFF TRAINING</Desc>
        <TotalAmt>75</TotalAmt>
        <FundraisingAmt>75</FundraisingAmt>
      </OtherExpensesGrp>
      <TotalFunctionalExpensesGrp>
        <TotalAmt>869590</TotalAmt>
        <ProgramServicesAmt>324280</ProgramServicesAmt>
        <ManagementAndGeneralAmt>235637</ManagementAndGeneralAmt>
        <FundraisingAmt>309673</FundraisingAmt>
      </TotalFunctionalExpensesGrp>
      <CashNonInterestBearingGrp>
        <BOYAmt>182657</BOYAmt>
        <EOYAmt>24750</EOYAmt>
      </CashNonInterestBearingGrp>
      <SavingsAndTempCashInvstGrp>
        <BOYAmt>280688</BOYAmt>
        <EOYAmt>198568</EOYAmt>
      </SavingsAndTempCashInvstGrp>
      <PledgesAndGrantsReceivableGrp>
        <BOYAmt>303430</BOYAmt>
        <EOYAmt>349623</EOYAmt>
      </PledgesAndGrantsReceivableGrp>
      <AccountsReceivableGrp>
        <BOYAmt>26650</BOYAmt>
        <EOYAmt>4576</EOYAmt>
      </AccountsReceivableGrp>
      <PrepaidExpensesDefrdChargesGrp>
        <BOYAmt>4953</BOYAmt>
        <EOYAmt>4007</EOYAmt>
      </PrepaidExpensesDefrdChargesGrp>
      <InvestmentsPubTradedSecGrp>
        <BOYAmt>12484606</BOYAmt>
        <EOYAmt>11619154</EOYAmt>
      </InvestmentsPubTradedSecGrp>
      <OtherAssetsTotalGrp>
        <BOYAmt>16755</BOYAmt>
        <EOYAmt>22433</EOYAmt>
      </OtherAssetsTotalGrp>
      <TotalAssetsGrp>
        <BOYAmt>13299739</BOYAmt>
        <EOYAmt>12223111</EOYAmt>
      </TotalAssetsGrp>
      <AccountsPayableAccrExpnssGrp>
        <BOYAmt>12606</BOYAmt>
        <EOYAmt>5894</EOYAmt>
      </AccountsPayableAccrExpnssGrp>
      <MortgNotesPyblScrdInvstPropGrp>
        <BOYAmt>0</BOYAmt>
        <EOYAmt>30042</EOYAmt>
      </MortgNotesPyblScrdInvstPropGrp>
      <TotalLiabilitiesGrp>
        <BOYAmt>12606</BOYAmt>
        <EOYAmt>35936</EOYAmt>
      </TotalLiabilitiesGrp>
      <OrganizationFollowsSFAS117Ind>X</OrganizationFollowsSFAS117Ind>
      <UnrestrictedNetAssetsGrp>
        <BOYAmt>2687213</BOYAmt>
        <EOYAmt>2278390</EOYAmt>
      </UnrestrictedNetAssetsGrp>
      <TemporarilyRstrNetAssetsGrp>
        <BOYAmt>753406</BOYAmt>
        <EOYAmt>-74382</EOYAmt>
      </TemporarilyRstrNetAssetsGrp>
      <PermanentlyRstrNetAssetsGrp>
        <BOYAmt>9846514</BOYAmt>
        <EOYAmt>9983167</EOYAmt>
      </PermanentlyRstrNetAssetsGrp>
      <TotalNetAssetsFundBalanceGrp>
        <BOYAmt>13287133</BOYAmt>
        <EOYAmt>12187175</EOYAmt>
      </TotalNetAssetsFundBalanceGrp>
      <TotLiabNetAssetsFundBalanceGrp>
        <BOYAmt>13299739</BOYAmt>
        <EOYAmt>12223111</EOYAmt>
      </TotLiabNetAssetsFundBalanceGrp>
      <ReconcilationRevenueExpnssAmt>411718</ReconcilationRevenueExpnssAmt>
      <NetUnrlzdGainsLossesInvstAmt>-1511676</NetUnrlzdGainsLossesInvstAmt>
      <OtherChangesInNetAssetsAmt>0</OtherChangesInNetAssetsAmt>
      <MethodOfAccountingAccrualInd>X</MethodOfAccountingAccrualInd>
      <AccountantCompileOrReviewInd>0</AccountantCompileOrReviewInd>
      <FSAuditedInd>1</FSAuditedInd>
      <FSAuditedBasisGrp>
        <ConsolAndSepBasisFinclStmtInd>X</ConsolAndSepBasisFinclStmtInd>
      </FSAuditedBasisGrp>
      <AuditCommitteeInd>1</AuditCommitteeInd>
      <FederalGrantAuditRequiredInd>0</FederalGrantAuditRequiredInd>
    </IRS990>
    <IRS990ScheduleA documentId="RetDoc1039100001">
      <SupportingOrganization509a3Ind>X</SupportingOrganization509a3Ind>
      <SupportingOrgType1Ind>X</SupportingOrgType1Ind>
      <SupportedOrganizationsCnt>1</SupportedOrganizationsCnt>
      <SupportedOrgInformationGrp>
        <SupportedOrganizationName>
          <BusinessNameLine1Txt>AMERICAN SOCIETY FOR RADIATION ONCOLOGY</BusinessNameLine1Txt>
        </SupportedOrganizationName>
        <EIN>420943164</EIN>
        <OrganizationTypeCd>10</OrganizationTypeCd>
        <GoverningDocumentListedInd>0</GoverningDocumentListedInd>
        <SupportAmt>10000</SupportAmt>
        <OtherSupportAmt>0</OtherSupportAmt>
      </SupportedOrgInformationGrp>
      <SupportedOrganizationsTotalCnt>1</SupportedOrganizationsTotalCnt>
      <SupportSumAmt>10000</SupportSumAmt>
      <OtherSupportSumAmt>0</OtherSupportSumAmt>
      <Form990SchASupportingOrgGrp>
        <ListedByNameGoverningDocInd>1</ListedByNameGoverningDocInd>
        <SuprtOrgNoIRSDeterminationInd>0</SuprtOrgNoIRSDeterminationInd>
        <SupportedOrgSectionC456Ind>1</SupportedOrgSectionC456Ind>
        <SupportedOrgQualifiedInd>1</SupportedOrgQualifiedInd>
        <SuprtExclusivelySec170c2BInd>0</SuprtExclusivelySec170c2BInd>
        <SupportedOrgNotOrganizedUSInd>0</SupportedOrgNotOrganizedUSInd>
        <OrganizationChangeSuprtOrgInd>0</OrganizationChangeSuprtOrgInd>
        <SupportNonSupportedOrgInd>0</SupportNonSupportedOrgInd>
        <PaymentSubstantialContribtrInd>0</PaymentSubstantialContribtrInd>
        <LoanDisqualifiedPersonInd>0</LoanDisqualifiedPersonInd>
        <ControlledDisqualifiedPrsnInd>0</ControlledDisqualifiedPrsnInd>
        <DisqualifiedPrsnControllIntInd>0</DisqualifiedPrsnControllIntInd>
        <DisqualifiedPrsnOwnrIntInd>0</DisqualifiedPrsnOwnrIntInd>
        <ExcessBusinessHoldingsRulesInd>0</ExcessBusinessHoldingsRulesInd>
        <ContributionControllerInd>0</ContributionControllerInd>
        <ContributionFamilyInd>0</ContributionFamilyInd>
        <Contribution35ControlledInd>0</Contribution35ControlledInd>
      </Form990SchASupportingOrgGrp>
      <Form990SchAType1SuprtOrgGrp>
        <PowerAppointMajorityDirTrstInd>1</PowerAppointMajorityDirTrstInd>
        <OperateBenefitNonSuprtOrgInd>0</OperateBenefitNonSuprtOrgInd>
      </Form990SchAType1SuprtOrgGrp>
      <Form990ScheduleAPartVIGrp>
        <FormAndLineReferenceDesc>PART IV, SECTION A, LINE 3B:</FormAndLineReferenceDesc>
        <ExplanationTxt>ROI IS THE SUPPORTING ORGANIZATION FOR THE AMERICAN SOCIETY FOR RADIATION ONCOLOGY (ASTRO), A 501(C)(6) ORGANIZATION. ROI PERFORMED THE 509(A)(2) TEST FOR ASTRO AND FOUND THAT ASTRO'S SUPPORT PERCENTAGE EXCEEDS THE 33% MINIMUM OF PUBLIC SUPPORT THAT WOULD BE A REQUIREMENT IF ASTRO WERE DESCRIBED AS SUCH AN ENTITY. ACCORDINGLY, ROI IS ELIGIBLE TO SUPPORT ASTRO.</ExplanationTxt>
      </Form990ScheduleAPartVIGrp>
    </IRS990ScheduleA>
    <IRS990ScheduleB documentId="RetDoc1234500001">
      <ContributorInformationGrp>
        <ContributorNum>RESTRICTED</ContributorNum>
        <ContributorBusinessName>
          <BusinessNameLine1>RESTRICTED</BusinessNameLine1>
        </ContributorBusinessName>
        <ContributorUSAddress>
          <AddressLine1>RESTRICTED</AddressLine1>
          <AddressLine2>RESTRICTED</AddressLine2>
          <City>RESTRICTED</City>
          <State>RESTRICTED</State>
          <ZIPCode>RESTRICTED</ZIPCode>
        </ContributorUSAddress>
        <TotalContributionsAmt>RESTRICTED</TotalContributionsAmt>
      </ContributorInformationGrp>
    </IRS990ScheduleB>
    <IRS990ScheduleD documentId="RetDoc1040000001">
      <CYEndwmtFundGrp>
        <BeginningYearBalanceAmt>10457820</BeginningYearBalanceAmt>
        <ContributionsAmt>136653</ContributionsAmt>
        <InvestmentEarningsOrLossesAmt>-771235</InvestmentEarningsOrLossesAmt>
        <OtherExpendituresAmt>267852</OtherExpendituresAmt>
        <EndYearBalanceAmt>9555386</EndYearBalanceAmt>
      </CYEndwmtFundGrp>
      <CYMinus1YrEndwmtFundGrp>
        <BeginningYearBalanceAmt>9169439</BeginningYearBalanceAmt>
        <ContributionsAmt>198633</ContributionsAmt>
        <InvestmentEarningsOrLossesAmt>1281972</InvestmentEarningsOrLossesAmt>
        <OtherExpendituresAmt>192224</OtherExpendituresAmt>
        <EndYearBalanceAmt>10457820</EndYearBalanceAmt>
      </CYMinus1YrEndwmtFundGrp>
      <CYMinus2YrEndwmtFundGrp>
        <BeginningYearBalanceAmt>9117677</BeginningYearBalanceAmt>
        <ContributionsAmt>158021</ContributionsAmt>
        <InvestmentEarningsOrLossesAmt>414950</InvestmentEarningsOrLossesAmt>
        <OtherExpendituresAmt>521209</OtherExpendituresAmt>
        <EndYearBalanceAmt>9169439</EndYearBalanceAmt>
      </CYMinus2YrEndwmtFundGrp>
      <CYMinus3YrEndwmtFundGrp>
        <BeginningYearBalanceAmt>9431266</BeginningYearBalanceAmt>
        <ContributionsAmt>272097</ContributionsAmt>
        <InvestmentEarningsOrLossesAmt>-172985</InvestmentEarningsOrLossesAmt>
        <OtherExpendituresAmt>412701</OtherExpendituresAmt>
        <EndYearBalanceAmt>9117677</EndYearBalanceAmt>
      </CYMinus3YrEndwmtFundGrp>
      <CYMinus4YrEndwmtFundGrp>
        <BeginningYearBalanceAmt>9041538</BeginningYearBalanceAmt>
        <ContributionsAmt>361072</ContributionsAmt>
        <InvestmentEarningsOrLossesAmt>441358</InvestmentEarningsOrLossesAmt>
        <OtherExpendituresAmt>412702</OtherExpendituresAmt>
        <EndYearBalanceAmt>9431266</EndYearBalanceAmt>
      </CYMinus4YrEndwmtFundGrp>
      <PrmnntEndowmentBalanceEOYPct>1.00000</PrmnntEndowmentBalanceEOYPct>
      <EndowmentsHeldUnrelatedOrgInd>0</EndowmentsHeldUnrelatedOrgInd>
      <EndowmentsHeldRelatedOrgInd>0</EndowmentsHeldRelatedOrgInd>
      <TotalBookValueLandBuildingsAmt>0</TotalBookValueLandBuildingsAmt>
      <FootnoteTextInd>X</FootnoteTextInd>
      <TotalRevEtcAuditedFinclStmtAmt>-243800</TotalRevEtcAuditedFinclStmtAmt>
      <NetUnrealizedGainsInvstAmt>-1511676</NetUnrealizedGainsInvstAmt>
      <DonatedServicesAndUseFcltsAmt>27098</DonatedServicesAndUseFcltsAmt>
      <RevenueNotReportedAmt>-1484578</RevenueNotReportedAmt>
      <RevenueSubtotalAmt>1240778</RevenueSubtotalAmt>
      <InvestmentExpensesNotIncldAmt>40530</InvestmentExpensesNotIncldAmt>
      <RevenueNotReportedFinclStmtAmt>40530</RevenueNotReportedFinclStmtAmt>
      <TotalRevenuePerForm990Amt>1281308</TotalRevenuePerForm990Amt>
      <TotExpnsEtcAuditedFinclStmtAmt>856158</TotExpnsEtcAuditedFinclStmtAmt>
      <DonatedServicesUseFcltsAmt>27098</DonatedServicesUseFcltsAmt>
      <ExpensesNotReportedAmt>27098</ExpensesNotReportedAmt>
      <ExpensesSubtotalAmt>829060</ExpensesSubtotalAmt>
      <InvestmentExpensesNotIncld2Amt>40530</InvestmentExpensesNotIncld2Amt>
      <ExpensesNotRptFinclStmtAmt>40530</ExpensesNotRptFinclStmtAmt>
      <TotalExpensesPerForm990Amt>869590</TotalExpensesPerForm990Amt>
      <SupplementalInformationDetail>
        <FormAndLineReferenceDesc>PART V, LINE 4:</FormAndLineReferenceDesc>
        <ExplanationTxt>CURRENTLY, THE ENDOWMENT FUND IS A PERMANENTLY RESTRICTED FUND WHICH IS NOT AVAILABLE FOR USE.</ExplanationTxt>
      </SupplementalInformationDetail>
      <SupplementalInformationDetail>
        <FormAndLineReferenceDesc>PART X, LINE 2:</FormAndLineReferenceDesc>
        <ExplanationTxt>ROI PERFORMED AN EVALUATION OF UNCERTAINTY IN INCOME TAXES FOR THE YEAR ENDED DECEMBER 31, 2018, AND DETERMINED THAT THERE ARE NO MATTERS THAT WOULD REQUIRE RECOGNITION IN THE FINANCIAL STATEMENTS OR THAT MAY HAVE ANY EFFECT ON ITS TAX-EXEMPT STATUS.</ExplanationTxt>
      </SupplementalInformationDetail>
    </IRS990ScheduleD>
    <IRS990ScheduleI documentId="RetDoc1041900001">
      <GrantRecordsMaintainedInd>1</GrantRecordsMaintainedInd>
      <RecipientTable>
        <RecipientBusinessName>
          <BusinessNameLine1Txt>JOHN HOPKINS UNIVERSITY</BusinessNameLine1Txt>
        </RecipientBusinessName>
        <USAddress>
          <AddressLine1Txt>3910 KESWICK ROAD N4327-B</AddressLine1Txt>
          <CityNm>BALTIMORE</CityNm>
          <StateAbbreviationCd>MD</StateAbbreviationCd>
          <ZIPCd>21211</ZIPCd>
        </USAddress>
        <RecipientEIN>520595110</RecipientEIN>
        <IRCSectionDesc>501(C)(3)</IRCSectionDesc>
        <CashGrantAmt>75000</CashGrantAmt>
        <PurposeOfGrantTxt>RESEARCH AWARDS</PurposeOfGrantTxt>
      </RecipientTable>
      <RecipientTable>
        <RecipientBusinessName>
          <BusinessNameLine1Txt>DUKE UNIVERSITY</BusinessNameLine1Txt>
        </RecipientBusinessName>
        <USAddress>
          <AddressLine1Txt>PO BOX 104132</AddressLine1Txt>
          <CityNm>DURHAM</CityNm>
          <StateAbbreviationCd>NC</StateAbbreviationCd>
          <ZIPCd>27708</ZIPCd>
        </USAddress>
        <RecipientEIN>560532129</RecipientEIN>
        <IRCSectionDesc>501(C)(3)</IRCSectionDesc>
        <CashGrantAmt>50971</CashGrantAmt>
        <PurposeOfGrantTxt>RESEARCH AWARDS</PurposeOfGrantTxt>
      </RecipientTable>
      <RecipientTable>
        <RecipientBusinessName>
          <BusinessNameLine1Txt>VANDERBILT UNIVERSITY MEDICAL CENTER</BusinessNameLine1Txt>
        </RecipientBusinessName>
        <USAddress>
          <AddressLine1Txt>3319 WEST END AVENUE SUITE 970</AddressLine1Txt>
          <CityNm>NASHVILLE</CityNm>
          <StateAbbreviationCd>TN</StateAbbreviationCd>
          <ZIPCd>37203</ZIPCd>
        </USAddress>
        <RecipientEIN>352528741</RecipientEIN>
        <IRCSectionDesc>501(C)(3)</IRCSectionDesc>
        <CashGrantAmt>50000</CashGrantAmt>
        <PurposeOfGrantTxt>RESEARCH AWARDS</PurposeOfGrantTxt>
      </RecipientTable>
      <RecipientTable>
        <RecipientBusinessName>
          <BusinessNameLine1Txt>MD ANDERSON CANCER CENTER</BusinessNameLine1Txt>
        </RecipientBusinessName>
        <USAddress>
          <AddressLine1Txt>1515 HOLCOMBE BOULEVARD</AddressLine1Txt>
          <CityNm>HOUSTON</CityNm>
          <StateAbbreviationCd>TX</StateAbbreviationCd>
          <ZIPCd>77230</ZIPCd>
        </USAddress>
        <RecipientEIN>746001118</RecipientEIN>
        <IRCSectionDesc>501(C)(3)</IRCSectionDesc>
        <CashGrantAmt>41251</CashGrantAmt>
        <PurposeOfGrantTxt>RESEARCH AWARDS</PurposeOfGrantTxt>
      </RecipientTable>
      <RecipientTable>
        <RecipientBusinessName>
          <BusinessNameLine1Txt>OREGON HEALTH &amp; SCIENCE UNIVERSITY</BusinessNameLine1Txt>
        </RecipientBusinessName>
        <USAddress>
          <AddressLine1Txt>3181 SW SAM JACKSON PARK ROAD</AddressLine1Txt>
          <CityNm>ARLINGTON</CityNm>
          <StateAbbreviationCd>VA</StateAbbreviationCd>
          <ZIPCd>22202</ZIPCd>
        </USAddress>
        <RecipientEIN>931176109</RecipientEIN>
        <IRCSectionDesc>SECTION 115 ORG</IRCSectionDesc>
        <CashGrantAmt>23817</CashGrantAmt>
        <PurposeOfGrantTxt>RESEARCH AWARDS</PurposeOfGrantTxt>
      </RecipientTable>
      <RecipientTable>
        <RecipientBusinessName>
          <BusinessNameLine1Txt>AMERICAN SOCIETY FOR RADIATION ONCOLOGY</BusinessNameLine1Txt>
        </RecipientBusinessName>
        <USAddress>
          <AddressLine1Txt>251 18TH STREET SOUTH 8TH FLOOR</AddressLine1Txt>
          <CityNm>ARLINGTON</CityNm>
          <StateAbbreviationCd>VA</StateAbbreviationCd>
          <ZIPCd>22202</ZIPCd>
        </USAddress>
        <RecipientEIN>420943164</RecipientEIN>
        <IRCSectionDesc>501(C)(6)</IRCSectionDesc>
        <CashGrantAmt>10000</CashGrantAmt>
        <PurposeOfGrantTxt>2018 ROI SUPPORT TO ARRO WEBIN</PurposeOfGrantTxt>
      </RecipientTable>
      <Total501c3OrgCnt>5</Total501c3OrgCnt>
      <TotalOtherOrgCnt>1</TotalOtherOrgCnt>
      <SupplementalInformationDetail>
        <FormAndLineReferenceDesc>PART I, LINE 2:</FormAndLineReferenceDesc>
        <ExplanationTxt>AS PER A SIGNED AGREEMENT LETTER, ROI REQUIRES ANY DEVIATION FROM THE FUNDED GRANT PROPOSAL TO BE SUBMITTED IMMEDIATELY IN WRITING TO ROI. IN ADDITION, AN INTERIM PROGRESS REPORT AND A FINAL REPORT ARE COLLECTED WHICH SUMMARIZE PROGRESS MADE AND EXPENDITURES.</ExplanationTxt>
      </SupplementalInformationDetail>
    </IRS990ScheduleI>
    <IRS990ScheduleJ documentId="RetDoc1042400001">
      <SeverancePaymentInd>0</SeverancePaymentInd>
      <SupplementalNonqualRtrPlanInd>0</SupplementalNonqualRtrPlanInd>
      <EquityBasedCompArrngmInd>0</EquityBasedCompArrngmInd>
      <CompBasedOnRevenueOfFlngOrgInd>0</CompBasedOnRevenueOfFlngOrgInd>
      <CompBsdOnRevRelatedOrgsInd>0</CompBsdOnRevRelatedOrgsInd>
      <CompBsdNetEarnsFlngOrgInd>0</CompBsdNetEarnsFlngOrgInd>
      <CompBsdNetEarnsRltdOrgsInd>0</CompBsdNetEarnsRltdOrgsInd>
      <AnyNonFixedPaymentsInd>0</AnyNonFixedPaymentsInd>
      <InitialContractExceptionInd>0</InitialContractExceptionInd>
      <RltdOrgOfficerTrstKeyEmplGrp>
        <PersonNm>LAURA I THEVENOT</PersonNm>
        <TitleTxt>EX-OFFICIO, EXECUTIVE DIRE</TitleTxt>
        <BaseCompensationFilingOrgAmt>0</BaseCompensationFilingOrgAmt>
        <CompensationBasedOnRltdOrgsAmt>492367</CompensationBasedOnRltdOrgsAmt>
        <BonusFilingOrganizationAmount>0</BonusFilingOrganizationAmount>
        <BonusRelatedOrganizationsAmt>97172</BonusRelatedOrganizationsAmt>
        <OtherCompensationFilingOrgAmt>0</OtherCompensationFilingOrgAmt>
        <OtherCompensationRltdOrgsAmt>62014</OtherCompensationRltdOrgsAmt>
        <DeferredCompensationFlngOrgAmt>0</DeferredCompensationFlngOrgAmt>
        <DeferredCompRltdOrgsAmt>38500</DeferredCompRltdOrgsAmt>
        <NontaxableBenefitsFilingOrgAmt>0</NontaxableBenefitsFilingOrgAmt>
        <NontaxableBenefitsRltdOrgsAmt>38731</NontaxableBenefitsRltdOrgsAmt>
        <TotalCompensationFilingOrgAmt>0</TotalCompensationFilingOrgAmt>
        <TotalCompensationRltdOrgsAmt>728784</TotalCompensationRltdOrgsAmt>
        <CompReportPrior990FilingOrgAmt>0</CompReportPrior990FilingOrgAmt>
        <CompReportPrior990RltdOrgsAmt>0</CompReportPrior990RltdOrgsAmt>
      </RltdOrgOfficerTrstKeyEmplGrp>
      <SupplementalInformationDetail>
        <FormAndLineReferenceDesc>PART I, LINE 3</FormAndLineReferenceDesc>
        <ExplanationTxt>ROI DOES NOT DIRECTLY HIRE OR COMPENSATE EMPLOYEES. ALL EMPLOYEES ARE EMPLOYEES OF THE AMERICAN SOCIETY FOR RADIATION ONCOLOGY (ASTRO), A RELATED ORGANIZATION EXEMPT UNDER SECTION 501(C)(6). AN INDEPENDENT CONSULTANT PERFORMED A MARKET SURVEY TO DEVELOP SALARY STRUCTURE AND RANGES. ASTRO'S PRACTICE IS TO COMPLETE A MARKET SURVEY EVERY THREE YEARS; THIS WAS LAST COMPLETED FOR THE EX-OFFICIO, EXECUTIVE DIRECTOR IN 2016. THE EX-OFFICIO, EXECUTIVE DIRECTOR'S COMPENSATION IS DETERMINED BY A SUBCOMMITTEE OF THE BOARD USING COMPARABLE SALARIES OF SIMILAR EXECUTIVE DIRECTOR POSITIONS OF NONPROFIT MEDICAL ORGANIZATIONS. THIS REVIEW WAS DISCUSSED WITH THE BOARD OF DIRECTORS AND THE FINAL DETERMINATION WAS MADE BY THE EXECUTIVE COMMITTEE.</ExplanationTxt>
      </SupplementalInformationDetail>
    </IRS990ScheduleJ>
    <IRS990ScheduleO documentId="RetDoc1044400001">
      <SupplementalInformationDetail>
        <FormAndLineReferenceDesc>FORM 990, PART VI, SECTION A, LINE 3</FormAndLineReferenceDesc>
        <ExplanationTxt>ALL MANAGEMENT FUNCTIONS OF ROI ARE CONTROLLED BY THE AMERICAN SOCIETY FOR RADIATION ONCOLOGY (ASTRO), A RELATED ORGANIZATION EXEMPT UNDER SECTION 501(C)(6).</ExplanationTxt>
      </SupplementalInformationDetail>
      <SupplementalInformationDetail>
        <FormAndLineReferenceDesc>FORM 990, PART VI, SECTION B, LINE 11B</FormAndLineReferenceDesc>
        <ExplanationTxt>THE FEDERAL FORM 990 IS PREPARED BY OUR EXTERNAL TAX ACCOUNTANTS. THE DRAFT IS PROVIDED TO OUR FINANCE STAFF FOR REVIEW BEFORE BEING SUBMITTED TO THE VP FINANCE &amp; ADMINISTRATION, CEO, AND TREASURER OF ASTRO FOR THEIR REVIEW AND APPROVAL. THE REVISED DRAFT IS THEN PROVIDED TO THE FULL BOARD OF DIRECTORS PRIOR TO FILING WITH THE INTERNAL REVENUE SERVICE.</ExplanationTxt>
      </SupplementalInformationDetail>
      <SupplementalInformationDetail>
        <FormAndLineReferenceDesc>FORM 990, PART VI, SECTION B, LINE 12C</FormAndLineReferenceDesc>
        <ExplanationTxt>ROI'S OFFICERS, DIRECTORS, KEY EMPLOYEES, AND VOLUNTEERS ARE REQUIRED TO FILL OUT DISCLOSURE FORMS ON AN ANNUAL BASIS AND TO UPDATE THEIR DISCLOSURE FORMS UPON ANY MATERIAL CHANGE IN THE INTERIM. THESE DISCLOSURE FORMS ARE REVIEWED IN ORDER TO IDENTIFY AND ADDRESS ANY POTENTIAL CONFLICTS OF THESE INDIVIDUALS.</ExplanationTxt>
      </SupplementalInformationDetail>
      <SupplementalInformationDetail>
        <FormAndLineReferenceDesc>FORM 990, PART VI, SECTION C, LINE 19</FormAndLineReferenceDesc>
        <ExplanationTxt>THE SUMMARY FINANCIAL STATEMENTS ARE AVAILABLE UPON REQUEST. GOVERNING DOCUMENTS AND CONFLICT OF INTEREST POLICY ARE AVAILABLE ON OUR WEBSITE.</ExplanationTxt>
      </SupplementalInformationDetail>
    </IRS990ScheduleO>
    <IRS990ScheduleR documentId="RetDoc1043400001">
      <IdRelatedTaxExemptOrgGrp>
        <DisregardedEntityName>
          <BusinessNameLine1Txt>AMERICAN SOCIETY FOR RADIATION ONCOLOGY</BusinessNameLine1Txt>
        </DisregardedEntityName>
        <USAddress>
          <AddressLine1Txt>251 18TH STREET SOUTH 8TH FLOOR</AddressLine1Txt>
          <CityNm>ARLINGTON</CityNm>
          <StateAbbreviationCd>VA</StateAbbreviationCd>
          <ZIPCd>22202</ZIPCd>
        </USAddress>
        <EIN>420943164</EIN>
        <PrimaryActivitiesTxt>MEMBERSHIP SOCIETY</PrimaryActivitiesTxt>
        <LegalDomicileStateCd>IL</LegalDomicileStateCd>
        <ExemptCodeSectionTxt>501(C)(6)</ExemptCodeSectionTxt>
        <PublicCharityStatusTxt>N/A</PublicCharityStatusTxt>
        <DirectControllingNACd>N/A</DirectControllingNACd>
        <ControlledOrganizationInd>0</ControlledOrganizationInd>
      </IdRelatedTaxExemptOrgGrp>
      <ReceiptOfIntAnntsRntsRyltsInd>0</ReceiptOfIntAnntsRntsRyltsInd>
      <GiftGrntOrCapContriToOthOrgInd>1</GiftGrntOrCapContriToOthOrgInd>
      <GiftGrntCapContriFromOthOrgInd>1</GiftGrntCapContriFromOthOrgInd>
      <LoansOrGuaranteesToOtherOrgInd>0</LoansOrGuaranteesToOtherOrgInd>
      <LoansOrGuaranteesFromOthOrgInd>0</LoansOrGuaranteesFromOthOrgInd>
      <DivRelatedOrganizationInd>0</DivRelatedOrganizationInd>
      <AssetSaleToOtherOrgInd>0</AssetSaleToOtherOrgInd>
      <AssetPurchaseFromOtherOrgInd>0</AssetPurchaseFromOtherOrgInd>
      <AssetExchangeInd>0</AssetExchangeInd>
      <RentalOfFacilitiesToOthOrgInd>0</RentalOfFacilitiesToOthOrgInd>
      <RentalOfFcltsFromOthOrgInd>0</RentalOfFcltsFromOthOrgInd>
      <PerformOfServicesForOthOrgInd>0</PerformOfServicesForOthOrgInd>
      <PerformOfServicesByOtherOrgInd>0</PerformOfServicesByOtherOrgInd>
      <SharingOfFacilitiesInd>1</SharingOfFacilitiesInd>
      <PaidEmployeesSharingInd>1</PaidEmployeesSharingInd>
      <ReimbursementPaidToOtherOrgInd>1</ReimbursementPaidToOtherOrgInd>
      <ReimbursementPaidByOtherOrgInd>1</ReimbursementPaidByOtherOrgInd>
      <TransferToOtherOrgInd>0</TransferToOtherOrgInd>
      <TransferFromOtherOrgInd>0</TransferFromOtherOrgInd>
      <TransactionsRelatedOrgGrp>
        <OtherOrganizationName>
          <BusinessNameLine1Txt>AMERICAN SOCIETY FOR RADIATION ONCOLOGY</BusinessNameLine1Txt>
        </OtherOrganizationName>
        <TransactionTypeTxt>C</TransactionTypeTxt>
        <InvolvedAmt>136653</InvolvedAmt>
        <MethodOfAmountDeterminationTxt>ACTUAL</MethodOfAmountDeterminationTxt>
      </TransactionsRelatedOrgGrp>
      <TransactionsRelatedOrgGrp>
        <OtherOrganizationName>
          <BusinessNameLine1Txt>AMERICAN SOCIETY FOR RADIATION ONCOLOGY</BusinessNameLine1Txt>
        </OtherOrganizationName>
        <TransactionTypeTxt>N</TransactionTypeTxt>
        <InvolvedAmt>139738</InvolvedAmt>
        <MethodOfAmountDeterminationTxt>FMV</MethodOfAmountDeterminationTxt>
      </TransactionsRelatedOrgGrp>
      <TransactionsRelatedOrgGrp>
        <OtherOrganizationName>
          <BusinessNameLine1Txt>AMERICAN SOCIETY FOR RADIATION ONCOLOGY</BusinessNameLine1Txt>
        </OtherOrganizationName>
        <TransactionTypeTxt>O</TransactionTypeTxt>
        <InvolvedAmt>291265</InvolvedAmt>
        <MethodOfAmountDeterminationTxt>FMV</MethodOfAmountDeterminationTxt>
      </TransactionsRelatedOrgGrp>
    </IRS990ScheduleR>
  </ReturnData>
</Return>