PDCD1 and neoplasm: In accordance with these findings, in two studies of a cohort of 20 advanced MM patients each, samples from patients treated with pembrolizumab or nivolumab [82,83], PFS, and response were positively correlated with ≥20% higher proportions of CD8+ T cells in tumor biopsies characterized by high surface expression of CTLA-4 and PD-1 [82,83], regardless of the anatomical site of biopsy or prior therapy.