CTLA4 and metastatic melanoma: In addition, given the small number of patients, we have carried out external validation with eight external cohorts of metastatic melanoma patients, six treated with anti-PD1, one treated with anti-PD1 + anti-CTLA4 and one treated with anti-CTLA4 in the context of five different studies [34,35,36,37,38] (Table S11).