Abstract Melanoma mortality particularly affects older patients, and age is a powerful independent predictor of death. The pathogenic mutations and transcriptomic changes associated with poor survival in aged patients are not known. We analyzed 5 cohorts of metastatic (N=324, N=18, N=66) and primary melanomas (N=103, N=30) to establish the effect of age on prognosis, identify age-specific driver genes and transcriptomic changes linked to survival and immunotherapy response. We identify the pathogenic mutations and transcriptomic changes associated with poor survival by age, and show mutations in BRAF, NRAS, CDKN2A or IDH1 identify metastatic and primary melanoma aged patients with worse outcome. In contrast, activation of immune-regulatory pathways is a hallmark of long-term survival. We tested if mutations in genes linked to poor outcome are associated to immunotherapy responders, exploring combinations of agespecific mutations in metastatic immune checkpoint inhibitor aged responders. Strikingly, aged patients with BRAF, NRAS, CDKN2A or IDH1 mutations and high tumor mutation burden treated with immunotherapy have an improved median survival of 12 months. These data highlight the molecular landscape of melanoma varies by age, and age stratification can refine prognosis and therapy rationales. A set of mutations identifies patients at highest risk of death who are likely immunotherapy responders.

MOLECULAR LANDSCAPE OF OLD AGE MELANOMA BY SURVIVAL AND IMMUNOTHERAPY RESPONSE