Overall Survival after Y-90 Selective Internal Radiotherapy of Liver Metastases in Oligometastatic Patients

Abstract

<h3>Purpose/Objective(s)</h3> Y-90 Selective Internal Radiotherapy (SIRT) is an ablative therapy used for patients with inoperable liver metastasis. The purpose of this investigation was to examine the impact of local control after SIRT on overall survival (OS) in oligometastatic patients, hypothesizing that local failure after SIRT would be correlated with lower OS. <h3>Materials/Methods</h3> A retrospective, single-institution, IRB-approved study selected oligometastatic patients defined as 5 or fewer total non-CNS metastases at the time of unilateral or bilateral lobar Y-90 SIRT from 2009 to 2021. Patients were staged with CT and/or MRI. The primary endpoint was OS defined from Y-90 SIRT completion to date of death or last follow-up. Local failure was classified as progressive disease at the target lesion(s) by RECIST v1.1 criteria starting at 3 months after SIRT. Failure was defined by imaging or if salvage locoregional therapy was performed. OS outcomes were calculated using the Kaplan-Meier method, and correlations with clinical variables were evaluated using log-rank testing. <h3>Results</h3> Twenty-three oligometastatic patients, with a total of 57 liver lesions, completed SIRT. The cohort was comprised of patients with colorectal adenocarcinoma (n=15), pancreatic adenocarcinoma (n=6), thymic carcinoma (n=1), and uveal melanoma (n=1). Fifteen patients (65%) received bilateral lobar SIRT and 8 (35%) received unilateral lobar treatment. Median follow up was 15.6 months (range 2.7-54.3). Twenty patients were treated with resin Y-90 microspheres and 3 received glass microspheres. On volumetric analysis of liver tumor burden, the range of liver involvement was 0.03% to 18.2%. The range of liver metastases was 1 to 5 with a median of 3. Of the 57 individual lesions treated, 19 (33%) failed. Fourteen patients (61%) failed in a treated lesion, including 9 as the first site of failure. Seven patients received salvage liver-directed therapy following intrahepatic failure; six received repeat SIRT. Seven patients did not receive post-SIRT chemotherapy, of which 5 experienced intralesional failure. Median OS (mOS) was 20.1 months, and 12-month OS was 68.6%. Metachronous versus synchronous metastasis at presentation was not found to be prognostic of OS (21.7 months vs 17.9 months (p<0.96)). Those with tumor involving <5% of the liver (n=17) had a mOS of 21.7 months vs 15.1 months for those with >5% (n=6) (p<0.12). Intralesional failure was associated with worse mOS (15.1 months vs. not reached, p<0.03). <h3>Conclusion</h3> These results suggest that intralesional failure following Y-90 may be associated with inferior OS, emphasizing the importance of disease control in low metastatic burden patients. Percentage of liver involvement may be predictive of local failure after SIRT. Larger prospective studies examining oligometastatic patients treated with SIRT are needed for further patient risk stratification.