Effect of HLA restriction on racial and ethnic disparities in access to immune therapies for advanced synovial sarcoma.

Purpose: Synovial sarcoma (SS) is aggressive with poor outcomes. Cellular therapies are now FDA approved for advanced disease, but are restricted to certain HLA-A*02 alleles. We estimate eligibility to cellular therapies by race and ethnicity.

Materials and methods: Demographic and clinical features of SS cases from 2001 to 2020 were obtained from the United States Cancer Statistics (USCS; NPCR-SEER). Survival analyses were performed overall and by races/ethnicity. The proportion eligible for cellular therapy was estimated by races/ethnicity using previously published data on HLA-A*02 status and MAGE-A4 positivity.

Results: From 2001 to 2020, 10,605 patients (48% female, 64% Non-Hispanic White, 17% Hispanic) with SS were identified. The incidence rate was 1.5-1.8/million/person-years and was stable over time, corresponding to an average 530 new cases annually. The most common primary site was the extremity (n = 5,877; 58%), and most patients presented with localized disease (n = 5,753; 54%). The 5-year cause-specific survival was 60% across all races/ethnicities and 79% for localized, 57% for regional, 12% for distant disease. Differences by race and ethnicity were found in the proportions of patients expected to be eligible for HLA-restricted cellular therapies targeting MAGE-A4. People of European/European descent had the highest estimated proportion (25-39%), and people of Asian/Pacific Islander descent had the lowest (11-17%).

Conclusion: Engineered T-cells targeting MAGE-A4 have shown encouraging safety and efficacy in advanced SS; however, eligibility restrictions will lead to racial and ethnic disparities. HLA-independent solutions must be developed to counter disparities and ensure all patients have access.