In a retrospective study involving head/neck cancer patients, treatment response to PD-1 inhibitors was associated with pre-treatment ALC; patients with ALC < 600 cells/μL had shorter progression free survival with PD-1 therapy compared to the cohort with ALC ≥ 600 cells/μL.36 Similarly, shorter time to progression was found in lymphopenic patients with solid tumors who were treated with nivolumab or pembrolizumab anti-PD-1 antibodies.17 The consideration that immunotherapy may be potentiated by enhancing lymphocyte counts warrants further study. Here, PDCD1 is linked to head and neck cancer.