PDCD1LG2 and head and neck squamous cell carcinoma: Similarly, although PD-L2 expression in TC was an independent prognostic factor for poor OS in operable HNSCC, in a small clinical study of R/M HNSCC, the PFS and the median time for overall survival in patients with positive PD-L2 expression were significantly longer than PD-L2-negative patients (20).