In the phase 2 study Keynote-055, in which patients with head and neck cSCC refractory to platinum and cetuximab were treated with pembrolizumab, no significant differences in response rates were observed between those with ≥ 50% PD-1 expression (i.e. percentage of tumor and mononuclear inflammatory cells within tumor nests and adjacent supporting stroma expressing PD-L1 at any intensity) and < 50% PD-1 expression (27% [95%CI 15–42] vs. 13% [95%CI 7–20], respectively) [61]. Here, CD274 is linked to neoplasm.