PDCD1 and melanoma: In this single-center, open-label, non-randomized dual cohort phase II clinical trial in patients with resected stage III or IV melanoma an experimental treatment regimen using a fixed low dose of the anti-PD-1 mAb nivolumab administered for one year was associated with encouraging efficacy and safety while a shorter combination regimen, including a single fixed dose of the anti-CTLA-4 mAb ipilimumab, resulted in a higher rate of adverse events and no indication for improved efficacy.