PDCD1 and metastatic melanoma: Despite the lack of a significant correlation between intratumoral PD-L1 expression and survival, PD-1/PD-L1 interactions in the tumor as measured by immune-Förster resonance energy transfer (iFRET) is more predictive of survival in metastatic melanoma and NSCLC patients receiving ICB, in line with findings in draining LNs (89, 100).