Outcomes of melanoma soft parts/clear cell sarcoma (MSP/CCS) patients (pts) with immune and targeted therapies.

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e21046 Background: Overall survival (OS) for pts with cutaneous melanoma has vastly improved with checkpoint inhibitors (CPI) and targeted therapy (TT), but less is known about outcomes of other rare tumors showing melanocytic differentiation. We examined outcomes for metastatic pts with MSP/CCS at MD Anderson (MDA) to characterize outcomes with contemporary therapies. Methods: Pts with MSP/CCS were identified in the MDA databases. Pts with < 2 visits to MDA or without molecular confirmation of dx were excluded. Log-rank testing was used to compare OS among distributions. Results: A total of 102 MSP/CCS pts were identified. Initial diagnosis was local disease 46%, regional metastases 34%, and systemic metastases 20%. Primary tumor site was lower extremity (LE) 48%, GI tract 29%, upper extremity (UE) 18%. 65 pts were diagnosed with metastatic disease (dz), including 32% with lung-only, 14% liver-only, and 51% with multiple metastatic sites. Median OS from diagnosis of distant metastatic dz was 22 mos (95% CI 16-34 mos). Primary tumor site (GI 46.4 vs. LE 19.1 vs. UE 14.7 mos; p = 0.018) and race (white 26.8 vs. black 6.5 mos, p = 0.019, HR 0.45) were significantly associated with OS from distant metastasis; sex, age, decade of diagnosis, size of primary, and prior treatment with neoadjuvant or adjuvant therapy were not. Treatments for metastatic dz included chemotherapy (n = 29), biochemotherapy (n = 11), biotherapy (n = 5), CPI (n = 11) and TT (n = 19). Median OS was 15.9 mos from start of CPI (range 10.7 to NR) and 16.9 mos from start of TT (range 7.8 to NR). Median OS from metastatic dz for pts not treated with CPI or TT was 17.1 mos (range 12.4 to 32.5), which was not significantly different versus CPI or TT. Duration of response was < 6 mos for 91% pts receiving CPI and 89% pts receiving TT. One pt had a durable response (41.8 mos) to anti-PD1 and one pt had a durable response (24.8 mos) to an AKT inhibitor. Conclusions: While rare responses to CPI and TT were observed, no significant difference was detected in OS compared to traditional therapies in pts with metastatic MSP/CCS. The development of more effective therapies remains an unmet need for this disease.