PDCD1 and non-small cell lung carcinoma: The timing of the proliferative response was shown to impact on the predictive ability of this biomarker in a study on NSCLC patients treated with pembrolizumab, where the PD-1+ CD8+ T cell proliferative response after a single dose of a PD-1 inhibitor was found to correlate with response only if it occurred within 4 weeks of treatment initiation [101].