Enrichment of somatic mosaic states involving DNA damage response and repair genes in patients treated with ¹⁷⁷Lutetium.

3020 Background: Radioligand therapy (RLT) use has been increasing with the approval of 177 Lu-Dotatate for metastatic neuroendocrine tumors (NET) & 177 Lu-PSMA-617 for metastatic castration resistant prostate cancer (mCRPC). Therapy-related myeloid neoplasms [tMN, including myelodysplastic syndrome (MDS) & acute myeloid leukemia, (AML)] have been reported after 177 Lutetium ( 177 Lu) for NET with rates of 2-20% & median time from first 177 Lu to tMN of 2.8yrs [4-12]. Clonal hematopoiesis (CH) is a risk factor for tMN, with the spectrum of CH depending on selection pressures. To describe the prevalence of therapy selected CH & tMN, we performed a retrospective analysis of patients (pts) who had a bone marrow biopsy (BMB) post- 177 Lu. Methods: After IRB approval, we queried the electronic health record for pts with BMB post- 177 Lu. Pt demographics, treatment history, labs & BMB results were collected. Results: Fifty-seven pts met criteria, 41 (72%) with NET & 16 (28%) with mCRPC. . Median age at BMB was 68yrs (range, 28-85). Of the 57pts, prior treatments included: radiation (RT) in 21 (37%), temozolomide in 14 (25%), taxane in 15 (26%), & platinum agents in 10 (18%). The median number of 177 Lu cycles was 4 (range, 1-11).Cytogenetics were available in 84% (n = 48) & were normal in 60% (n = 29). Of those with abnormal cytogenetics (n = 18, 38%), the most common abnormalities involved chromosome (chr) 7 (n = 12, 26%), chr 5 (n = 7, 15%), chr 20 (n = 5, 11%) and complex karyotypes in 7 (15%), with 3 (17%) of these patients having no mutations. Diagnoses were assessable in 49 (86%) pts: 15 (31%) with undefined cytopeniasand 16 (33%) with tMDS. Metastatic carcinoma was identified in 17 Fifty-one percent (n = 29), at a median of 0.5yrs (range, 0.04-2.6) after hematologic diagnosis. Conclusions: The enrichment of CH involving the DDR pathway in recipients of 177 Lu underscores the impact of RLT on bone marrow progenitors.