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

// Angela M Hong 1 , Ricardo E Vilain 2, 3 , Sarah Romanes 4 , Jean Yang 4 , Elizabeth Smith 2 , Deanna Jones 1 , Richard A Scolyer 1, 2 , C Soon Lee 1, 2, 5 , Mei Zhang 1 , Barbara Rose 1 1 Sydney Medical School, The University of Sydney, NSW, Australia 2 Tissue Pathology and Diagnostic Oncology, Royal Prince Alfred Hospital, NSW, Australia 3 Pathology North (Hunter), John Hunter Hospital, Newcastle, NSW, Australia 4 School of Mathematics and Statistics, The University of Sydney, NSW, Australia 5 Discipline of Pathology, School of Medicine, Western Sydney University, NSW, Australia Correspondence to: Angela M Hong, email: angela.hong@sydney.edu.au Keywords: tonsillar cancer, oropharyngeal cancer, human papillomavirus, PD-L1, p16 Received: August 15, 2016      Accepted: October 13, 2016      Published: October 20, 2016 ABSTRACT 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.