Immune checkpoint inhibitors-associated risk of immune-related hypothyroidism in older patients with advanced melanoma: a real-world analysis of US SEER-Medicare data.

Background: The risk of immune-related(ir)-hypothyroidism in older patients with advanced melanoma treated with anti-CTLA4 or anti-PD1 therapies is poorly understood, especially in the real-world setting. Research design and methods: We identified older patients (≥65 years) diagnosed with advanced melanoma between 2011-2015 and treated with anti-CTLA4 or anti-PD1 agents in the SEER-Medicare database. Applying probability-of-treatment-weighting for confounder adjustment and proportional hazards models, we estimated the risk of ir-hypothyroidism between treatment initiation and up to 90 days from last dose between anti-PD1 and anti-CTLA4 users. Results: Of 210 older patients with advanced melanoma identified, 164 received anti-CTLA4 (ipilimumab) and 46 anti-PD1 agents (11 nivolumab, 35 pembrolizumab). There was no statistically significant difference in ir-hypothyroidism risk between anti-PD1 and anti-CTLA4 users (HR=2.15, 95%CI=0.83-5.53). Pairwise medication comparisons showed a lower risk among ipilimumab versus nivolumab (HR=0.15, 95%CI=0.06-0.40) and pembrolizumab versus nivolumab users (HR=0.13, 95%CI=0.03-0.55). Sensitivity analyses using an all-stages melanoma cohort did not show a difference in ir-hypothyroidism risk between medication classes and individual medications. Conclusions: This retrospective claims data analysis revealed no statistically significant difference in ir-hypothyroidism risk between anti-CTLA4 or anti-PD1 users. However, patients with advanced melanoma treated with ipilimumab or pembrolizumab may have a lower ir-hypothyroidism risk compared to nivolumab users.