The influence of human papilloma virus (HPV) infection on the outcome of subjects with anal squamous cell carcinoma.

Abstract

e15152 Background: HPV infection is a risk factor for the development of anal cancer. P16 expression correlates highly with HPV infection. The influence of HPV infection on the outcome of these subjects has not been well defined. To evaluate the influence of HPV infection on prognosis of subjects with anal squamous cell cancer, a retrospective analysis was conducted. Methods: Subjects with anal squamous cell cancer diagnosed at the University of Arkansas for Medical Sciences between 1992 and 2010, were identified from the tumor registry. The charts were reviewed to confirm the diagnosis, stage, treatment and outcome of the subjects. Paraffin tissue blocks of the subjects were stained for p16 expression using the immunoperoxidase method using mouse monoclonal antibody (Clone E6H4) and CINTek Histology VKit. Slides were scanned to digital file (Aperio CS, Aperio, Vista, CA). Neoplastic regions were analyzed using a color deconvolution algorithm (Aperio). Based on the percentage of pixels with weak, moderate, strong, and negative staining, each slide was given a score between 0-300. Score of 150 and above was designated as positive. P16 positive and negative groups were compared for differences in recurrence-free survival (RFS) and overall survival (OS) via log-rank test. Results: There were 19 deaths observed among 33 study-eligible subjects during 103.2 person-years of follow-up. The median age (quartiles) was 53 (45-61) years. Males were 55%; Caucasians were 94%. All subjects were treated with chemotherapy and radiation. 26 subjects were p16 positive and 7 were p16 negative. The median RFS was 2.99 years for the p16-positive group vs. 1.90 years for the p16-negative group (p = 0.32). The median OS was 3.14 years for p16-positives vs. 2.00 years for p16-negatives, (p = 0.52). Conclusions: 78% of the patients with anal squamous cell cancer in our study were p16-positive. The RFS and OS tended to be longer for patients with p16-positive cancer, but the lack of statistical significance might be explained by the small number of p16-negative subjects. A larger study needs to be conducted to further evaluate the difference. [Table: see text]