Immune-Related Thyroiditis as a Predictor for Survival in Metastatic Renal Cell Carcinoma

Immune checkpoint inhibitors (CPI) are indicated for metastatic renal cell carcinoma (mRCC). Immune-related thyroiditis (irT), an immune-related adverse event (irAE), affects up to 30% of patients. We aimed to determine whether irT is associated with overall survival in mRCC. A retrospective cohort study of 123 consecutive patients treated with CPI for mRCC in a single center between 2015 and 2020 was conducted. Disease risk stratification was assessed by two methods: Heng criteria and a novel dichotomic stratification system to "Low risk" versus "High risk" adding number of metastatic sites. Thirty-eight percent of patients developed irT. In the general cohort, irT was not associated with a survival benefit. However, irT was associated with better survival in the poor risk group per Heng criteria (n = 17, HR = 0.25, p = 0.04) and in the novel "High risk" group (HR = 0.28, n = 42, p = 0.01), including after accounting for covariates in multivariate analysis (HR = 0.27, p = 0.003). Having any irAE was associated with improved survival in the whole cohort, with no significant correlation of any specific irAE, in either the whole cohort or the "High risk" group. We conclude that irT is an early and prevalent irAE, associated with prolonged survival in patients with poor/"High" risk mRCC.