PDCD1 and melanoma: More recently, a retrospective study compared young adult melanoma patients ≤40 years to older age groups, and found no overall difference in immunotherapy response based on age, but young adults had a significantly higher response rate (53% vs 38%) and improved PFS (median 13.7 vs 4.0 months) with combination ICI (anti-PD-1+anti-CTLA-4) compared to monotherapy12.