Introduction: Several types of immune checkpoint inhibitors (ICIs) are approved to treat advanced melanoma, but their effectiveness has not been compared in older patients treated outside of a clinical trial. Moreover, evidence suggests that a patient's response to ICI therapy may vary by age and type of ICI. The purpose of this study was to compare survival by ICI type in older patients with melanoma and to investigate treatment effect modification by age.
Materials and methods: Using the SEER-Medicare database, we identified patients with cutaneous melanoma (2012-2015) treated with an ICI (CTLA-4, PD-1, or combination CTLA-4 + PD-1 inhibitors). Cox proportional hazards regression was used to estimate hazard ratios (HRs) with 95% confidence intervals (CI) for ICI types. We used an interaction term and stratified models to test for treatment effect modification by age.
Results: Of the 1435 patients included in our analysis, 790 (55.1%) received CTLA-4 inhibitors, 512 (35.7%) received PD-1 inhibitors, and 133 (9.3%) were treated with combination ICIs. Median survival ranged from 13.4 months (95%CI: 10.7-16.3) for CTLA-4 inhibitors to 23.5 months (95%CI: 16.2-30.0) for combination ICIs. In multivariable models, the risk of death was lower with PD-1 inhibitors compared to CTLA-4 inhibitors (HR = 0.78, 95%CI: 0.68-0.89). An age*ICI type interaction term was significant (p < 0.001), and survival gains were greater the older age group (≥80) compared to the younger group (65-79).
Discussion: In a population-based setting, we identified important differences in survival by ICI type in older patients with melanoma treated with ICIs, with prolonged survival associated with PD-1 inhibitors compared to CTLA-4 inhibitors.
Keywords: Aged; Immunological antineoplastic agents; Medicare; Melanoma; Survival analysis.
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