TP53 and cancer: Although ATM is a recurrently mutated DNA repair gene in cancer, it does not have a well-described mutational signature associated with it.30 Hence, to evaluate whether newly identified pathogenic mutations in AlphaMissense were functional, we relied on well-described genetic associations with ATM mutations (mutual exclusivity with TP53 mutations) and previously described responses to RT.11,30 Among 2,153 patients with ATM missense mutations in the MSK-IMPACT cohort, 610 (28.3%) had newly identified pathogenic ATM mutations (Data Supplement, Table S6).