Although the external performance of the CA209-538 strain–response signature fell short of what is required for clinical use, its performance was remarkably better in CICB (AUC = 0.67, 0.40, 0.78 and 0.75) than anti-PD-1 (AUC = 0.46, 0.44, 0.58 and 0.54) melanoma cohorts from other industrialized countries. This evidence concerns the gene PDCD1 and melanoma.