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      <Form990PartVIISectionAGrp>
        <PersonNm>DAVE ADLER</PersonNm>
        <TitleTxt>VP ADVOCACY &amp; CLINICAL AFFAIRS</TitleTxt>
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      <Form990PartVIISectionAGrp>
        <PersonNm>LAURA GOGAL</PersonNm>
        <TitleTxt>GENERAL COUNSEL</TitleTxt>
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      <Form990PartVIISectionAGrp>
        <PersonNm>JUDY KEEN</PersonNm>
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      <Form990PartVIISectionAGrp>
        <PersonNm>ANNE HUBBARD</PersonNm>
        <TitleTxt>DIRECTOR OF HEALTH POLICY</TitleTxt>
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      <Form990PartVIISectionAGrp>
        <PersonNm>AMY NORDENG</PersonNm>
        <TitleTxt>ASSOCIATE GENERAL COUNSEL</TitleTxt>
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      <Form990PartVIISectionAGrp>
        <PersonNm>ANNA ARNONE</PersonNm>
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      <ContractorCompensationGrp>
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          <USAddress>
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            <StateAbbreviationCd>TX</StateAbbreviationCd>
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      <ContractorCompensationGrp>
        <ContractorName>
          <BusinessName>
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        <ContractorAddress>
          <USAddress>
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      <ContractorCompensationGrp>
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            <BusinessNameLine1Txt>ELSEVIER</BusinessNameLine1Txt>
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          <USAddress>
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      <ContractorCompensationGrp>
        <ContractorName>
          <BusinessName>
            <BusinessNameLine1Txt>MARRIOTT BUSINESS SERVICES</BusinessNameLine1Txt>
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        <ContractorAddress>
          <USAddress>
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      <ContractorCompensationGrp>
        <ContractorName>
          <BusinessName>
            <BusinessNameLine1Txt>GLOBAL EXPERIENCE SPECIALIST</BusinessNameLine1Txt>
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          <USAddress>
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      <ProgramServiceRevenueGrp>
        <Desc>MEMBERSHIP DUES</Desc>
        <BusinessCd>900099</BusinessCd>
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        <RelatedOrExemptFuncIncomeAmt>3655731</RelatedOrExemptFuncIncomeAmt>
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      <ProgramServiceRevenueGrp>
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        <BusinessCd>900099</BusinessCd>
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      <ProgramServiceRevenueGrp>
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      <ProgramServiceRevenueGrp>
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        <BusinessCd>900099</BusinessCd>
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        <BookValueAmt>316418</BookValueAmt>
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        <Desc>DEFERRED RENT AND LEASEHOLD INCENTIVE</Desc>
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      </OtherLiabilitiesOrgGrp>
      <OtherLiabilitiesOrgGrp>
        <Desc>DEFERRED COMPENSATION LIABILITY</Desc>
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      <OtherLiabilitiesOrgGrp>
        <Desc>DUE TO AFFILIATES</Desc>
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      <FootnoteTextInd>X</FootnoteTextInd>
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      <RevenueNotReportedFinclStmtAmt>98392</RevenueNotReportedFinclStmtAmt>
      <TotalRevenuePerForm990Amt>22166053</TotalRevenuePerForm990Amt>
      <TotExpnsEtcAuditedFinclStmtAmt>21279397</TotExpnsEtcAuditedFinclStmtAmt>
      <ExpensesNotReportedAmt>0</ExpensesNotReportedAmt>
      <ExpensesSubtotalAmt>21279397</ExpensesSubtotalAmt>
      <InvestmentExpensesNotIncld2Amt>98392</InvestmentExpensesNotIncld2Amt>
      <ExpensesNotRptFinclStmtAmt>98392</ExpensesNotRptFinclStmtAmt>
      <TotalExpensesPerForm990Amt>21377789</TotalExpensesPerForm990Amt>
      <SupplementalInformationDetail>
        <FormAndLineReferenceDesc>PART X, LINE 2:</FormAndLineReferenceDesc>
        <ExplanationTxt>ASTRO 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 CONSOLIDATED 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>RADIATION ONCOLOGY INSTITUTE</BusinessNameLine1Txt>
        </RecipientBusinessName>
        <USAddress>
          <AddressLine1Txt>251 18TH STREET SOUTH 8TH FLOOR</AddressLine1Txt>
          <CityNm>ARLINGTON</CityNm>
          <StateAbbreviationCd>VA</StateAbbreviationCd>
          <ZIPCd>22202</ZIPCd>
        </USAddress>
        <RecipientEIN>510178702</RecipientEIN>
        <IRCSectionDesc>501(C)(3)</IRCSectionDesc>
        <CashGrantAmt>136653</CashGrantAmt>
        <PurposeOfGrantTxt>PROGRAM SUPPORT</PurposeOfGrantTxt>
      </RecipientTable>
      <RecipientTable>
        <RecipientBusinessName>
          <BusinessNameLine1Txt>DANA-FARBER CANCER INSTITUTE</BusinessNameLine1Txt>
        </RecipientBusinessName>
        <USAddress>
          <AddressLine1Txt>MAIL STOP BP451 450 BROOKLINE AVE</AddressLine1Txt>
          <CityNm>BOSTON</CityNm>
          <StateAbbreviationCd>MA</StateAbbreviationCd>
          <ZIPCd>022155450</ZIPCd>
        </USAddress>
        <RecipientEIN>042263040</RecipientEIN>
        <IRCSectionDesc>501(C)(3)</IRCSectionDesc>
        <CashGrantAmt>112500</CashGrantAmt>
        <PurposeOfGrantTxt>YOUNG INVESTIGATOR AWARD</PurposeOfGrantTxt>
      </RecipientTable>
      <RecipientTable>
        <RecipientBusinessName>
          <BusinessNameLine1Txt>UNIVERSITY OF MICHIGAN</BusinessNameLine1Txt>
        </RecipientBusinessName>
        <USAddress>
          <AddressLine1Txt>3003 SOUTH STATE STREET</AddressLine1Txt>
          <CityNm>ANN ARBOR</CityNm>
          <StateAbbreviationCd>MI</StateAbbreviationCd>
          <ZIPCd>48109</ZIPCd>
        </USAddress>
        <RecipientEIN>386006309</RecipientEIN>
        <IRCSectionDesc>N/A</IRCSectionDesc>
        <CashGrantAmt>100000</CashGrantAmt>
        <PurposeOfGrantTxt>YOUNG INVESTIGATOR AWARD</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>25000</CashGrantAmt>
        <PurposeOfGrantTxt>SEED GRANTS</PurposeOfGrantTxt>
      </RecipientTable>
      <RecipientTable>
        <RecipientBusinessName>
          <BusinessNameLine1Txt>STANFORD UNIVERSITY</BusinessNameLine1Txt>
        </RecipientBusinessName>
        <USAddress>
          <AddressLine1Txt>269 CAMPUS DRIVE WEST</AddressLine1Txt>
          <CityNm>STANFORD</CityNm>
          <StateAbbreviationCd>CA</StateAbbreviationCd>
          <ZIPCd>94305</ZIPCd>
        </USAddress>
        <RecipientEIN>941156365</RecipientEIN>
        <IRCSectionDesc>501(C)(3)</IRCSectionDesc>
        <CashGrantAmt>25000</CashGrantAmt>
        <PurposeOfGrantTxt>SEED GRANTS</PurposeOfGrantTxt>
      </RecipientTable>
      <RecipientTable>
        <RecipientBusinessName>
          <BusinessNameLine1Txt>JOHN HOPKINS UNIVERSITY</BusinessNameLine1Txt>
        </RecipientBusinessName>
        <USAddress>
          <AddressLine1Txt>733 N BROADWAY SUITE 117</AddressLine1Txt>
          <CityNm>BALTIMORE</CityNm>
          <StateAbbreviationCd>MD</StateAbbreviationCd>
          <ZIPCd>21205</ZIPCd>
        </USAddress>
        <RecipientEIN>520595110</RecipientEIN>
        <IRCSectionDesc>501(C)(3)</IRCSectionDesc>
        <CashGrantAmt>9267</CashGrantAmt>
        <PurposeOfGrantTxt>SEED GRANTS/AAPM</PurposeOfGrantTxt>
      </RecipientTable>
      <Total501c3OrgCnt>6</Total501c3OrgCnt>
      <TotalOtherOrgCnt>0</TotalOtherOrgCnt>
      <SupplementalInformationDetail>
        <FormAndLineReferenceDesc>PART I, LINE 2:</FormAndLineReferenceDesc>
        <ExplanationTxt>ASTRO AWARDS GRANTS WHICH REQUIRE SPECIFIC DELIVERABLES, AND ACCORDINGLY, THE FUNDS MUST BE USED TO ACCOMPLISH A DEFINED PURPOSE. THE SEED GRANT (ONE-YEAR GRANT) IS MONITORED BY A SIX-MONTH PROGRESS REPORT AND A FINAL REPORT. JUNIOR FACULTY CAREER RESEARCH AWARDS (2-YEAR GRANTS) ARE MONITORED BY A PROGRESS REPORT AFTER THE FIRST YEAR AND A FINAL REPORT AT THE END OF THE SECOND YEAR.</ExplanationTxt>
      </SupplementalInformationDetail>
    </IRS990ScheduleI>
    <IRS990ScheduleJ documentId="RetDoc1042400001">
      <SubstantiationRequiredInd>1</SubstantiationRequiredInd>
      <CompensationCommitteeInd>X</CompensationCommitteeInd>
      <IndependentConsultantInd>X</IndependentConsultantInd>
      <Form990OfOtherOrganizationsInd>X</Form990OfOtherOrganizationsInd>
      <CompensationSurveyInd>X</CompensationSurveyInd>
      <BoardOrCommitteeApprovalInd>X</BoardOrCommitteeApprovalInd>
      <SeverancePaymentInd>0</SeverancePaymentInd>
      <SupplementalNonqualRtrPlanInd>1</SupplementalNonqualRtrPlanInd>
      <EquityBasedCompArrngmInd>0</EquityBasedCompArrngmInd>
      <RltdOrgOfficerTrstKeyEmplGrp>
        <PersonNm>LAURA I THEVENOT</PersonNm>
        <TitleTxt>CEO</TitleTxt>
        <BaseCompensationFilingOrgAmt>492367</BaseCompensationFilingOrgAmt>
        <CompensationBasedOnRltdOrgsAmt>0</CompensationBasedOnRltdOrgsAmt>
        <BonusFilingOrganizationAmount>97172</BonusFilingOrganizationAmount>
        <BonusRelatedOrganizationsAmt>0</BonusRelatedOrganizationsAmt>
        <OtherCompensationFilingOrgAmt>62014</OtherCompensationFilingOrgAmt>
        <OtherCompensationRltdOrgsAmt>0</OtherCompensationRltdOrgsAmt>
        <DeferredCompensationFlngOrgAmt>38500</DeferredCompensationFlngOrgAmt>
        <DeferredCompRltdOrgsAmt>0</DeferredCompRltdOrgsAmt>
        <NontaxableBenefitsFilingOrgAmt>38731</NontaxableBenefitsFilingOrgAmt>
        <NontaxableBenefitsRltdOrgsAmt>0</NontaxableBenefitsRltdOrgsAmt>
        <TotalCompensationFilingOrgAmt>728784</TotalCompensationFilingOrgAmt>
        <TotalCompensationRltdOrgsAmt>0</TotalCompensationRltdOrgsAmt>
        <CompReportPrior990FilingOrgAmt>0</CompReportPrior990FilingOrgAmt>
        <CompReportPrior990RltdOrgsAmt>0</CompReportPrior990RltdOrgsAmt>
      </RltdOrgOfficerTrstKeyEmplGrp>
      <RltdOrgOfficerTrstKeyEmplGrp>
        <PersonNm>TERRY KARRAS</PersonNm>
        <TitleTxt>CFO</TitleTxt>
        <BaseCompensationFilingOrgAmt>169721</BaseCompensationFilingOrgAmt>
        <CompensationBasedOnRltdOrgsAmt>0</CompensationBasedOnRltdOrgsAmt>
        <BonusFilingOrganizationAmount>2000</BonusFilingOrganizationAmount>
        <BonusRelatedOrganizationsAmt>0</BonusRelatedOrganizationsAmt>
        <OtherCompensationFilingOrgAmt>0</OtherCompensationFilingOrgAmt>
        <OtherCompensationRltdOrgsAmt>0</OtherCompensationRltdOrgsAmt>
        <DeferredCompensationFlngOrgAmt>17698</DeferredCompensationFlngOrgAmt>
        <DeferredCompRltdOrgsAmt>0</DeferredCompRltdOrgsAmt>
        <NontaxableBenefitsFilingOrgAmt>22288</NontaxableBenefitsFilingOrgAmt>
        <NontaxableBenefitsRltdOrgsAmt>0</NontaxableBenefitsRltdOrgsAmt>
        <TotalCompensationFilingOrgAmt>211707</TotalCompensationFilingOrgAmt>
        <TotalCompensationRltdOrgsAmt>0</TotalCompensationRltdOrgsAmt>
        <CompReportPrior990FilingOrgAmt>0</CompReportPrior990FilingOrgAmt>
        <CompReportPrior990RltdOrgsAmt>0</CompReportPrior990RltdOrgsAmt>
      </RltdOrgOfficerTrstKeyEmplGrp>
      <RltdOrgOfficerTrstKeyEmplGrp>
        <PersonNm>EMILY WILSON</PersonNm>
        <TitleTxt>EXECUTIVE VICE PRESIDENT</TitleTxt>
        <BaseCompensationFilingOrgAmt>232867</BaseCompensationFilingOrgAmt>
        <CompensationBasedOnRltdOrgsAmt>0</CompensationBasedOnRltdOrgsAmt>
        <BonusFilingOrganizationAmount>3000</BonusFilingOrganizationAmount>
        <BonusRelatedOrganizationsAmt>0</BonusRelatedOrganizationsAmt>
        <OtherCompensationFilingOrgAmt>0</OtherCompensationFilingOrgAmt>
        <OtherCompensationRltdOrgsAmt>0</OtherCompensationRltdOrgsAmt>
        <DeferredCompensationFlngOrgAmt>24130</DeferredCompensationFlngOrgAmt>
        <DeferredCompRltdOrgsAmt>0</DeferredCompRltdOrgsAmt>
        <NontaxableBenefitsFilingOrgAmt>10361</NontaxableBenefitsFilingOrgAmt>
        <NontaxableBenefitsRltdOrgsAmt>0</NontaxableBenefitsRltdOrgsAmt>
        <TotalCompensationFilingOrgAmt>270358</TotalCompensationFilingOrgAmt>
        <TotalCompensationRltdOrgsAmt>0</TotalCompensationRltdOrgsAmt>
        <CompReportPrior990FilingOrgAmt>0</CompReportPrior990FilingOrgAmt>
        <CompReportPrior990RltdOrgsAmt>0</CompReportPrior990RltdOrgsAmt>
      </RltdOrgOfficerTrstKeyEmplGrp>
      <RltdOrgOfficerTrstKeyEmplGrp>
        <PersonNm>DAVE ADLER</PersonNm>
        <TitleTxt>VP ADVOCACY &amp; CLINICAL AFFAIRS</TitleTxt>
        <BaseCompensationFilingOrgAmt>184915</BaseCompensationFilingOrgAmt>
        <CompensationBasedOnRltdOrgsAmt>0</CompensationBasedOnRltdOrgsAmt>
        <BonusFilingOrganizationAmount>2000</BonusFilingOrganizationAmount>
        <BonusRelatedOrganizationsAmt>0</BonusRelatedOrganizationsAmt>
        <OtherCompensationFilingOrgAmt>0</OtherCompensationFilingOrgAmt>
        <OtherCompensationRltdOrgsAmt>0</OtherCompensationRltdOrgsAmt>
        <DeferredCompensationFlngOrgAmt>19453</DeferredCompensationFlngOrgAmt>
        <DeferredCompRltdOrgsAmt>0</DeferredCompRltdOrgsAmt>
        <NontaxableBenefitsFilingOrgAmt>22114</NontaxableBenefitsFilingOrgAmt>
        <NontaxableBenefitsRltdOrgsAmt>0</NontaxableBenefitsRltdOrgsAmt>
        <TotalCompensationFilingOrgAmt>228482</TotalCompensationFilingOrgAmt>
        <TotalCompensationRltdOrgsAmt>0</TotalCompensationRltdOrgsAmt>
        <CompReportPrior990FilingOrgAmt>0</CompReportPrior990FilingOrgAmt>
        <CompReportPrior990RltdOrgsAmt>0</CompReportPrior990RltdOrgsAmt>
      </RltdOrgOfficerTrstKeyEmplGrp>
      <RltdOrgOfficerTrstKeyEmplGrp>
        <PersonNm>LAURA GOGAL</PersonNm>
        <TitleTxt>GENERAL COUNSEL</TitleTxt>
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        <CompensationBasedOnRltdOrgsAmt>0</CompensationBasedOnRltdOrgsAmt>
        <BonusFilingOrganizationAmount>1000</BonusFilingOrganizationAmount>
        <BonusRelatedOrganizationsAmt>0</BonusRelatedOrganizationsAmt>
        <OtherCompensationFilingOrgAmt>0</OtherCompensationFilingOrgAmt>
        <OtherCompensationRltdOrgsAmt>0</OtherCompensationRltdOrgsAmt>
        <DeferredCompensationFlngOrgAmt>20164</DeferredCompensationFlngOrgAmt>
        <DeferredCompRltdOrgsAmt>0</DeferredCompRltdOrgsAmt>
        <NontaxableBenefitsFilingOrgAmt>3510</NontaxableBenefitsFilingOrgAmt>
        <NontaxableBenefitsRltdOrgsAmt>0</NontaxableBenefitsRltdOrgsAmt>
        <TotalCompensationFilingOrgAmt>224414</TotalCompensationFilingOrgAmt>
        <TotalCompensationRltdOrgsAmt>0</TotalCompensationRltdOrgsAmt>
        <CompReportPrior990FilingOrgAmt>0</CompReportPrior990FilingOrgAmt>
        <CompReportPrior990RltdOrgsAmt>0</CompReportPrior990RltdOrgsAmt>
      </RltdOrgOfficerTrstKeyEmplGrp>
      <RltdOrgOfficerTrstKeyEmplGrp>
        <PersonNm>JUDY KEEN</PersonNm>
        <TitleTxt>DIRECTOR OF SCIENTIFIC AFFAIRS</TitleTxt>
        <BaseCompensationFilingOrgAmt>156648</BaseCompensationFilingOrgAmt>
        <CompensationBasedOnRltdOrgsAmt>0</CompensationBasedOnRltdOrgsAmt>
        <BonusFilingOrganizationAmount>2000</BonusFilingOrganizationAmount>
        <BonusRelatedOrganizationsAmt>0</BonusRelatedOrganizationsAmt>
        <OtherCompensationFilingOrgAmt>0</OtherCompensationFilingOrgAmt>
        <OtherCompensationRltdOrgsAmt>0</OtherCompensationRltdOrgsAmt>
        <DeferredCompensationFlngOrgAmt>16517</DeferredCompensationFlngOrgAmt>
        <DeferredCompRltdOrgsAmt>0</DeferredCompRltdOrgsAmt>
        <NontaxableBenefitsFilingOrgAmt>18558</NontaxableBenefitsFilingOrgAmt>
        <NontaxableBenefitsRltdOrgsAmt>0</NontaxableBenefitsRltdOrgsAmt>
        <TotalCompensationFilingOrgAmt>193723</TotalCompensationFilingOrgAmt>
        <TotalCompensationRltdOrgsAmt>0</TotalCompensationRltdOrgsAmt>
        <CompReportPrior990FilingOrgAmt>0</CompReportPrior990FilingOrgAmt>
        <CompReportPrior990RltdOrgsAmt>0</CompReportPrior990RltdOrgsAmt>
      </RltdOrgOfficerTrstKeyEmplGrp>
      <RltdOrgOfficerTrstKeyEmplGrp>
        <PersonNm>ANNE HUBBARD</PersonNm>
        <TitleTxt>DIRECTOR OF HEALTH POLICY</TitleTxt>
        <BaseCompensationFilingOrgAmt>150928</BaseCompensationFilingOrgAmt>
        <CompensationBasedOnRltdOrgsAmt>0</CompensationBasedOnRltdOrgsAmt>
        <BonusFilingOrganizationAmount>3500</BonusFilingOrganizationAmount>
        <BonusRelatedOrganizationsAmt>0</BonusRelatedOrganizationsAmt>
        <OtherCompensationFilingOrgAmt>0</OtherCompensationFilingOrgAmt>
        <OtherCompensationRltdOrgsAmt>0</OtherCompensationRltdOrgsAmt>
        <DeferredCompensationFlngOrgAmt>16169</DeferredCompensationFlngOrgAmt>
        <DeferredCompRltdOrgsAmt>0</DeferredCompRltdOrgsAmt>
        <NontaxableBenefitsFilingOrgAmt>21615</NontaxableBenefitsFilingOrgAmt>
        <NontaxableBenefitsRltdOrgsAmt>0</NontaxableBenefitsRltdOrgsAmt>
        <TotalCompensationFilingOrgAmt>192212</TotalCompensationFilingOrgAmt>
        <TotalCompensationRltdOrgsAmt>0</TotalCompensationRltdOrgsAmt>
        <CompReportPrior990FilingOrgAmt>0</CompReportPrior990FilingOrgAmt>
        <CompReportPrior990RltdOrgsAmt>0</CompReportPrior990RltdOrgsAmt>
      </RltdOrgOfficerTrstKeyEmplGrp>
      <RltdOrgOfficerTrstKeyEmplGrp>
        <PersonNm>AMY NORDENG</PersonNm>
        <TitleTxt>ASSOCIATE GENERAL COUNSEL</TitleTxt>
        <BaseCompensationFilingOrgAmt>150660</BaseCompensationFilingOrgAmt>
        <CompensationBasedOnRltdOrgsAmt>0</CompensationBasedOnRltdOrgsAmt>
        <BonusFilingOrganizationAmount>0</BonusFilingOrganizationAmount>
        <BonusRelatedOrganizationsAmt>0</BonusRelatedOrganizationsAmt>
        <OtherCompensationFilingOrgAmt>0</OtherCompensationFilingOrgAmt>
        <OtherCompensationRltdOrgsAmt>0</OtherCompensationRltdOrgsAmt>
        <DeferredCompensationFlngOrgAmt>16299</DeferredCompensationFlngOrgAmt>
        <DeferredCompRltdOrgsAmt>0</DeferredCompRltdOrgsAmt>
        <NontaxableBenefitsFilingOrgAmt>21900</NontaxableBenefitsFilingOrgAmt>
        <NontaxableBenefitsRltdOrgsAmt>0</NontaxableBenefitsRltdOrgsAmt>
        <TotalCompensationFilingOrgAmt>188859</TotalCompensationFilingOrgAmt>
        <TotalCompensationRltdOrgsAmt>0</TotalCompensationRltdOrgsAmt>
        <CompReportPrior990FilingOrgAmt>0</CompReportPrior990FilingOrgAmt>
        <CompReportPrior990RltdOrgsAmt>0</CompReportPrior990RltdOrgsAmt>
      </RltdOrgOfficerTrstKeyEmplGrp>
      <RltdOrgOfficerTrstKeyEmplGrp>
        <PersonNm>ANNA ARNONE</PersonNm>
        <TitleTxt>VP MEMBER RELATIONS &amp; COMMUNICATIONS</TitleTxt>
        <BaseCompensationFilingOrgAmt>145715</BaseCompensationFilingOrgAmt>
        <CompensationBasedOnRltdOrgsAmt>0</CompensationBasedOnRltdOrgsAmt>
        <BonusFilingOrganizationAmount>2000</BonusFilingOrganizationAmount>
        <BonusRelatedOrganizationsAmt>0</BonusRelatedOrganizationsAmt>
        <OtherCompensationFilingOrgAmt>0</OtherCompensationFilingOrgAmt>
        <OtherCompensationRltdOrgsAmt>0</OtherCompensationRltdOrgsAmt>
        <DeferredCompensationFlngOrgAmt>15212</DeferredCompensationFlngOrgAmt>
        <DeferredCompRltdOrgsAmt>0</DeferredCompRltdOrgsAmt>
        <NontaxableBenefitsFilingOrgAmt>18842</NontaxableBenefitsFilingOrgAmt>
        <NontaxableBenefitsRltdOrgsAmt>0</NontaxableBenefitsRltdOrgsAmt>
        <TotalCompensationFilingOrgAmt>181769</TotalCompensationFilingOrgAmt>
        <TotalCompensationRltdOrgsAmt>0</TotalCompensationRltdOrgsAmt>
        <CompReportPrior990FilingOrgAmt>0</CompReportPrior990FilingOrgAmt>
        <CompReportPrior990RltdOrgsAmt>0</CompReportPrior990RltdOrgsAmt>
      </RltdOrgOfficerTrstKeyEmplGrp>
      <SupplementalInformationDetail>
        <FormAndLineReferenceDesc>PART I, LINE 4B</FormAndLineReferenceDesc>
        <ExplanationTxt>DURING THE YEAR ENDED DECEMBER 31, 2018, LAURA THEVENOT, CEO, PARTICIPATED IN A 457(F) NONQUALIFIED PLAN, WITH CONTRIBUTIONS TO THE PLAN OF $11,000.</ExplanationTxt>
      </SupplementalInformationDetail>
    </IRS990ScheduleJ>
    <IRS990ScheduleO documentId="RetDoc1044400001">
      <SupplementalInformationDetail>
        <FormAndLineReferenceDesc>FORM 990, PART VI, SECTION A, LINE 6</FormAndLineReferenceDesc>
        <ExplanationTxt>ASTRO'S NOMINATING COMMITTEE IS COMPRISED OF EIGHT PERSONS ELECTED FROM ITS MEMBERSHIP. THE NOMINATING COMMITTEE IS RESPONSIBLE FOR FINALIZING THE SLATE OF CANDIDATES FOR THE BOARD OF DIRECTORS.</ExplanationTxt>
      </SupplementalInformationDetail>
      <SupplementalInformationDetail>
        <FormAndLineReferenceDesc>FORM 990, PART VI, SECTION A, LINE 7A</FormAndLineReferenceDesc>
        <ExplanationTxt>REFER TO EXPLANATION PROVIDED IN RESPONSE TO LINE 6 FOR A DESCRIPTION OF THE MEMBERS WITH THE RIGHT TO ELECT THE GOVERNING BODY.</ExplanationTxt>
      </SupplementalInformationDetail>
      <SupplementalInformationDetail>
        <FormAndLineReferenceDesc>FORM 990, PART VI, SECTION A, LINE 7B</FormAndLineReferenceDesc>
        <ExplanationTxt>REFER TO EXPLANATION PROVIDED IN RESPONSE TO LINE 6 FOR A DESCRIPTION OF THE MEMBERS WITH THE RIGHT TO PARTICIPATE IN ASTRO'S GOVERNANCE.</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 FOR THEIR REVIEW AND APPROVAL. THE REVISED DRAFT IS THEN PROVIDED TO THE FULL BOARD OF DIRECTORS FOR THEIR REVIEW PRIOR TO FILING WITH THE INTERNAL REVENUE SERVICE.</ExplanationTxt>
      </SupplementalInformationDetail>
      <SupplementalInformationDetail>
        <FormAndLineReferenceDesc>FORM 990, PART VI, SECTION B, LINE 12C</FormAndLineReferenceDesc>
        <ExplanationTxt>ASTRO'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 INTERESTS FOR THESE INDIVIDUALS.</ExplanationTxt>
      </SupplementalInformationDetail>
      <SupplementalInformationDetail>
        <FormAndLineReferenceDesc>FORM 990, PART VI, SECTION B, LINE 15</FormAndLineReferenceDesc>
        <ExplanationTxt>AN INDEPENDENT CONSULTANT PERFORMED 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 CEO IN 2016. THE CEO'S COMPENSATION IS DETERMINED BY A SUBCOMMITTEE OF THE BOARD USING COMPARABLE SALARIES OF SIMILAR CEO POSITIONS OF NONPROFIT MEDICAL ORGANIZATIONS. THIS REVIEW WAS DISCUSSED WITH THE BOARD OF DIRECTORS AND RECEIVED THEIR APPROVAL. ANNUALLY, BUDGET GUIDELINES ARE SET FOR ANY ADDITIONS TO STAFF AND SALARY INCREASES. MANAGERS MAKE RECOMMENDATIONS FOR ANNUAL INCREASES AND PROMOTIONS WHICH ARE REVIEWED BY HUMAN RESOURCES AND THE DIVISION VICE PRESIDENTS. ALL PROMOTIONS ARE APPROVED BY THE CHIEF EXECUTIVE OFFICER.</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>
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      <IdRelatedTaxExemptOrgGrp>
        <DisregardedEntityName>
          <BusinessNameLine1Txt>RADIATION ONCOLOGY INSTITUTE</BusinessNameLine1Txt>
        </DisregardedEntityName>
        <USAddress>
          <AddressLine1Txt>251 18TH STREET SOUTH 8TH FLOOR</AddressLine1Txt>
          <CityNm>ARLINGTON</CityNm>
          <StateAbbreviationCd>VA</StateAbbreviationCd>
          <ZIPCd>22202</ZIPCd>
        </USAddress>
        <EIN>510178702</EIN>
        <PrimaryActivitiesTxt>TO SUPPORT AND CONDUCT RESEARCH AND EDUCATIONAL ACTIVITIES</PrimaryActivitiesTxt>
        <LegalDomicileStateCd>IL</LegalDomicileStateCd>
        <ExemptCodeSectionTxt>501(C)(3)</ExemptCodeSectionTxt>
        <PublicCharityStatusTxt>LINE 12B, II</PublicCharityStatusTxt>
        <DirectControllingEntityName>
          <BusinessNameLine1Txt>ASTRO</BusinessNameLine1Txt>
        </DirectControllingEntityName>
        <ControlledOrganizationInd>1</ControlledOrganizationInd>
      </IdRelatedTaxExemptOrgGrp>
      <IdRelatedTaxExemptOrgGrp>
        <DisregardedEntityName>
          <BusinessNameLine1Txt>ASTRO PAC</BusinessNameLine1Txt>
        </DisregardedEntityName>
        <USAddress>
          <AddressLine1Txt>251 18TH STREET SOUTH 8TH FLOOR</AddressLine1Txt>
          <CityNm>ARLINGTON</CityNm>
          <StateAbbreviationCd>VA</StateAbbreviationCd>
          <ZIPCd>22202</ZIPCd>
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      <GiftGrntCapContriFromOthOrgInd>1</GiftGrntCapContriFromOthOrgInd>
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      <DivRelatedOrganizationInd>0</DivRelatedOrganizationInd>
      <AssetSaleToOtherOrgInd>0</AssetSaleToOtherOrgInd>
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      <PerformOfServicesForOthOrgInd>0</PerformOfServicesForOthOrgInd>
      <PerformOfServicesByOtherOrgInd>0</PerformOfServicesByOtherOrgInd>
      <SharingOfFacilitiesInd>1</SharingOfFacilitiesInd>
      <PaidEmployeesSharingInd>1</PaidEmployeesSharingInd>
      <ReimbursementPaidToOtherOrgInd>1</ReimbursementPaidToOtherOrgInd>
      <ReimbursementPaidByOtherOrgInd>1</ReimbursementPaidByOtherOrgInd>
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      <TransferFromOtherOrgInd>0</TransferFromOtherOrgInd>
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        <OtherOrganizationName>
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      <TransactionsRelatedOrgGrp>
        <OtherOrganizationName>
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      </TransactionsRelatedOrgGrp>
      <TransactionsRelatedOrgGrp>
        <OtherOrganizationName>
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</Return>