Characteristics and impact of programmed death-ligand 1 expression, CD8+ tumor-infiltrating lymphocytes, and p16 status in head and neck squamous cell carcinoma

BACKGROUND

No predictive biomarker of immune checkpoint inhibitors in head and neck squamous cell carcinoma (HNSCC) has been well established. The impact of programmed death-ligand 1 (PD-L1) expression, CD8+ tumor-infiltrating lymphocytes (TILs), and p16 status in HNSCC is unclear and may vary according to ethnicity.

METHODS

HNSCC patients treated between 2007 and 2013 were reviewed. Archival tissues were retrieved for PD-L1, CD8+ TILs, and p16 analyses. PD-L1 expression was evaluated by using the validated SP142 assay on the VENTANA platform. CD8+ TILs were defined by using semiquantitative scoring.

RESULTS

A total of 203 patients were analyzed. PD-L1 expression was observed in 80% of patients and was significantly associated with older age (P < 0.001). A high CD8+ TIL score (≥ 6) was significantly associated with never-smoking (P = 0.020), oral cavity cancer (P < 0.001), and stage M0 at presentation (P = 0.025). The p16 status was positive in 12% of patients. Patients with a high TIL score had a significantly longer OS (P = 0.032). Patients with PD-L1 expression of 1-49% and ≥ 50% were associated with a significantly shorter OS compared with those with PD-L1 < 1% (P = 0.027 and P = 0.011, respectively). Multivariate analysis showed that PD-L1 ≥ 50% was significantly associated with a poor OS. (HR 2.98 [95% CI 1.2-7.39]; P = 0.019.) CONCLUSIONS: A high prevalence of PD-L1 expression was observed in HNSCC using the validated SP142 assay. PD-L1 expression was associated with older age, while highly PD-L1 expression (≥ 50%) was an independent prognostic factor for poor OS in anti-PD1/PD-L1 untreated HNSCC patients.

PD-1 and PD-L1 expression in HNSCC primary cancer and related lymph node metastasis - impact on clinical outcome

AIMS

Expression profiles and clinical impact of programmed cell death ligand 1 (PD-L1) and programmed cell death 1 (PD-1) expressing tumour infiltrating lymphocytes (TILs) in head and neck squamous cell carcinoma (HNSCC) are not elucidated fully. This study evaluates expression patterns in primary HNSCC and related lymph node metastasis and the impact on patients' clinical outcome.

METHODS AND RESULTS

Immunohistochemical staining patterns of PD-L1 and PD-1 were evaluated in 129 specimens of primary HNSCC and 77 lymph node metastases. Results were correlated with patients' clinical data. PD-L1 expression was observed in 36% of primary carcinoma and 33% of lymph node metastasis, and correlates significantly with decreased overall survival (OS) (P = 0.01) and disease-free survival (DFS) (P = 0.001) in oral cavity squamous cell carcinoma patients. PD-L1 expression was associated with presence of lymph node metastasis (P = 0.0223). Infiltration of PD-1-expressing lymphocytes correlates significantly with favourable OS (P = 0.001) and DFS (P = 0.001) in oropharyngeal cancer and hypopharyngeal cancer patients OS (P = 0.007) and DFS (P = 0.001). Presence of PD-1 TILs also correlates significantly with better OS (P = 0.005) and DFS (P = 0) in the human papilloma virus (HPV)-negative cohort. Cox regression multivariate analysis revealed PD-1 TIL expression as an independent prognostic marker for OS (P = 0.004) and DFS (P = 0.001) and T stage was validated as negative prognostic marker for OS (P = 0.011). PD-1-expressing lymphocytes (P = 0.0412) and PD-L1 expression (P = 0.0022) patterns correlate significantly in primary cancers and matched lymph node metastases.

CONCLUSIONS

Our results characterise the expression profiles of PD-1 axis proteins in HNSCC which might serve as possible clinical prognostic markers.

Checkpoint cluster: biomarkers of response

Current clinical knowledge surrounding one of the most promising immune checkpoint pathways, namely programmed cell death-1 (PD-1) and its ligands PD-L1 and PD-L2, is reviewed in the context of head and neck squamous cell carcinoma. The results of two phase III clinical trials (KEYNOTE 040 and CheckMate 141) are critically examined. The utility of predictive biomarkers of response to immune checkpoint blockade, such as PD-L1/PD-L2 protein expression, interferon-gamma gene expression signatures, and mutational and neoantigen load, is discussed. Finally, we project future directions in the immuno-oncology field by discussing other promising predictive biomarkers as well as areas where the next advances are likely to take place, such as in the implementation of immune checkpoint inhibitors earlier in the course of cancer treatment and/or in combination therapies.