Differences in PD-L1, PD-L2, and EGFR Expression Between Naive and Recurrent Tumors in Patients With Head and Neck Squamous Cell Carcinoma: A Retrospective Study.

BACKGROUND: The efficacy of anti-PD-1 and EGFR therapies for head and neck squamous cell carcinoma (HNSCC) can be predicted using various markers; however, the stability of these markers remains unclear. METHODS: In this retrospective study, laboratory findings and tissue expression of PD-L1, PD-L2, and EGFR were analyzed in 79 paired naive and recurrent HNSCC tumors. Laboratory findings were also analyzed in nonrecurrent patients using a propensity score-matched analysis. PD-L1 and PD-L2 expression levels were assessed using tumor proportion score (TPS) and combined positive score (CPS), whereas EGFR was evaluated using the H-score. RESULTS: White blood cell, neutrophil, lymphocyte, and monocyte counts and lymphocyte-monocyte ratios were significantly lower in the patients after the first-line treatment regardless of recurrence. PD-L1, PD-L2, and EGFR expression changed in 30%-40% of tumor pairs. Immune but not tumoral PD-L1 positivity rates were significantly higher in the patients with early recurrence. CONCLUSIONS: The expression of immune checkpoints including PD-L1 in naive tumors does not reflect those in recurrent tumors. Increasing PD-L1 expression in immune cells may cause early recurrence of HNSCC.