PD-L1 expression in head and neck squamous cell carcinoma and its clinical significance: A prospective observational study from a tertiary care centre.

Background: Programmed Death Ligand 1 (PD-L1) expression in tumor cells contribute to tumor immunity and therapies directed against it, have shown encouraging results in recent years. As there is limited data on the significance of PD-L1 expression in Head and Neck Squamous Cell Carcinoma (HNSCC) from India, we aimed to study the PD-L1 expression and its relation with different clinic-pathological parameters in patients of HNSCC from a tertiary care center in Eastern India.

Methods: A prospective evaluation of HNSCC patients diagnosed and managed at our center over a period of two and half years, was performed. PD-L1 expression in formalin fixed-paraffin embedded tumor tissue specimens was measured using SP-263 (Ventana) and 22C3 (Dako). A PD-L1 expression of <1%, 1-19%, ≥20% were considered negative, low, and high expression, respectively, and was correlated with various parameters.

Results: A total of 71 patients (mean age 50.8 ± 13.3 years, 86% males) were diagnosed with HNSCC (buccal mucosa-28, tongue-22, rest of oral cavity-8, larynx-7, nasopharynx-6). The tumor was poorly differentiated in 12 (17%). PD-L1 positivity was seen in a total of 51 (71.8%) patients (1-19%:18, ≥20%:33). Thirty (85.7%) patients among those aged <50 years and 58.3% of those aged ≥50 years showed PD-L1 positivity which was significant (P = 0.01). There were no statistically significant differences in PD-L1 positivity with respect to gender, tobacco use, tumor grade as well as tumor and nodal stage. Median follow up duration was 18 months (range 3-31 months) and there was significant difference in overall survival among PD-L1 positive and negative groups (31 vs 24 months; log rank P = 0.03).

Conclusions: 72% of HNSCC patients in our cohort showed PD-L1 positivity and it was not associated with any patient demographic characteristics or aggressive pathological features. Positive PD-L1 expression may have a beneficial effect on overall survival in HNSCC.