CD8+ and CD4+ Tumour Infiltrating Lymphocytes in Relation to Human Papillomavirus Status and Clinical Outcome in Tonsillar and Base of Tongue Squamous Cell Carcinoma

Patients with human papillomavirus (HPV) positive tonsillar and base of tongue squamous cell carcinoma (TSCC and BOTSCC, respectively) have a better clinical outcome than those with HPV negative tumours, irrespective of treatment. However, to better individualise treatment, additional biomarkers are needed together with HPV status. In a pilot study, we showed that high numbers of CD8(+) tumour infiltrating lymphocytes (TILs) in HPVDNA+ p16(INK4a+) TSCC indicated a better outcome. Here this study was extended. Totally 203 TSCC and 77 BOTSCC formalin fixed paraffin embedded tumour biopsies, earlier tested for HPV DNA (79% HPVDNA+) and p16(INK4a) from patients treated with curative intention, were analysed for CD8(+) and CD4(+) TILs by immunohistochemistry. Data obtained for 275 patients were correlated to HPVDNA and p16(INK4a) status, overall survival (OS) and disease free survival (DFS). In both HPVDNA+ and HPVDNA+ p16(INK4a+) tumours higher CD8(+) TIL counts correlated to a better 3-year OS (logrank test, both p<0.001) and 3-year DFS (logrank test, p = 0.003 and p = 0.004 respectively) as compared to the lowest quartile in the groups. A similar pattern was observed when analysing TSCC alone, while for BOTSCC significance was obtained only for 3-year OS. In HPVDNA- tumours the trend was similar, but significance was obtained again only for 3-year OS. The number of CD4(+) TILs did not generally correlate to survival. In conclusion, in HPVDNA+ and/or HPVDNA+ p16(INK4a+) tumours high CD8(+) TIL counts indicated a better 3-year OS. This suggests that high CD8(+) TIL counts together with HPVDNA+ or HPVDNA+ p16(INK4a+) could be used when selecting patients for more individualised treatment.