Healthcare disparities in Merkel cell carcinoma (MCC) in immune checkpoint inhibitor (ICI) era: A SEER study of survival disparities in older adults.

Abstract

e21602 Background: MCC is an aggressive type of neuroendocrine skin cancer, with an incidence of 1.0 to 9.8 (per 100,000 person-years) in adults aged 60–64 and 85+ years respectively. For patients undergoing cytotoxic chemotherapy in advanced MCC, the reported median progression-free survival was only three months, until the advent of ICI, which was first approved in 2017 as treatment for patients with metastatic MCC. Here we report the survival differences post ICI. Methods: We retrospectively collected data from the SEER database (Surveillance, Epidemiology, and End Results) Research Plus Data. We identified 9331 patients 65 and older diagnosed with MCC using ICD code 8247/3 from 2000 to 2021. We analyzed survival trends and clinical outcomes based on age, gender, ethnicity, socioeconomic status, and place of residence to evaluate the role of ICI in older MCC patients before and after 2017 (FDA approved ICI for MCC). Median survival times were calculated for each time period and compared using the log-rank test. For multivariate analysis, a Cox proportional hazards regression model was applied to examine the association between time period and five-year survival time, irrespective of the cause of death. Results: The median overall survival (mOS) time for all patients diagnosed with MCC was 8 months longer post 2017, (45 months, 95% CI 42 to 52 months) compared to pre 2017 (37 months, 95% CI 35 to 39 months). The adjusted HR post to pre 2017 was 0.87 (95% CI 0.81 to 0.93, P value <0.0001). Comparable results were found using Fine-Gray sub distribution hazard model: HR=0.87, 95% CI 0.79 to 0.96, p=0.005. mOS from 2000-2021 was 63 months in Hispanics, 33 months among blacks, and 38 months in Whites with p<0.0001. Among MCC patients living in metropolitan areas, mOS was 40 months compared to 32 months (p=0.0016) for those in non-metropolitan areas. In patients with median household income of $40,000-54,000, $55,000-74,999, $75,000-94,999 and $95,000+, mOS was 32, 36, 42 and 43 months respectively (p=0.0003). Males had worse survival with mOS of 33 months (HR 1.261 95% CI 1.199 to 1.326, p<0.0001), compared to females whose mOS was 51 months. Conclusions: These findings highlight the survival benefits of ICI in MCC compared to chemotherapy. There was a statistical difference in mOS before and after 2017 in males, females, Whites, and patients living in metropolitan area (refer to table). By examining disparities in survival based on gender, race, household income and residential areas, we identified potential areas for improvement in healthcare delivery of appropriate therapy. Subgroup analysis of each time period. Pre 2017 2017 and later p-value mOS (in months) 37 45 P = 0.000133 Age <70 119 Not reached (NR) P = 0.0772 Age >80 24 28 P = 0.0696 Male 31 39 P = 0.0002 Female 48 58 P = 0.0078 Whites 35 44 P <0.0001 Blacks 28 38 P = 0.2931 Hispanics 66 54 P = 0.9600 Metro 49 NR P = 0.0211 Non metro 30 38 P = 0.2057