In line with our findings, Music et al31 have recently reported an increase in plasma levels of PD-1 in response to pembrolizumab in a mixed cancer cohort of 24 patients, among them 9 patients with CM.31 Interestingly, they report an increase in PD-1 7 weeks after treatment initiation, suggesting that the early elevation detected in our study remains later on during treatment. The gene discussed is PDCD1; the disease is cancer.