PD-L1 expression in tonsillar cancer is associated with human papillomavirus positivity and improved survival: implications for anti-PD1 clinical trials

In this study, we examined PD-L1 expression by immunohistochemistry in 99 patients with tonsillar cancer and known human papillomavirus (HPV) status to assess its clinical significance. We showed that the pattern of PD-L1 expression is strongly related to HPV status. The PD-L1 positivity rate was 83.3% in HPV-positive cases and 56.9% in HPV-negative cases (p < 0.05). Patients with HPV-positive/PD-L1-positive cancer had significantly better event free survival and overall survival compared with patients with HPV-negative/PD-L1-negative cancer. Relative to those patients with HPV-negative/PD-L1-negative disease who had the highest risk of death, patients with HPV-positive/PD-L1-positive cancers had a 2.85 fold lower risk of developing an event (HR 0.35, 95% CI: 0.16-0.79) and a 4.5 fold lower risk of death (HR =0.22, 95% CI: 0.09-0.53). Our findings will help to guide future clinical trial design in immunotherapy based on PD-L1 expression in tonsillar cancer.