A total of 2129 patients who received ICI therapy were included (252 [11.8%] with MUC16 variant; median [interquartile range] age, 63.0 [54.0-71.0] years; 1255 [58.9%] men), of whom 595 (28.0%) had melanoma, 510 (24.0%) had non–small cell lung cancer (NSCLC), and 1024 (48.1%) had 12 other cancer types. The gene discussed is MUC16; the disease is lung cancer.