Prevalence and genotyping of HPV in anal squamous cell carcinoma

Abstract

Introduction: Anal squamous cell carcinomas (ASCC) account for approximately 2% of all gastrointestinal malignancies. The annual incidence of ASCC has increased by 2.9% per year in recent decades. In 2012, according to GLOBOCAN, 40,000 cases of anal cancer were reported worldwide, 35,000 (87%) attributable to HPV, being HPV-16 the most frequent serotype. A highly active HPV infection is associated with a more immunogenic tumor microenvironment with strong expression of immune markers, such as CD8+ and PD- 1+ tumor infiltrating lymphocytes (TILs), PD-L1+, FOXP3+ Tregs, caspase 8. Methods: 52 FFPE samples of patients with histologically confirmed ASCC were analyzed for HPV genotyping. The DNA, from the histological sections (previous step of deparaffinization) and the swab cells were purified using the QIAamp DNA Mini Kit that included 36 HPV genotypes. A retrospective review of the medical records was performed to correlate clinical data and treatment response with HPV results. The FFPE samples analyzed were exclusively obtained from the primary tumor. The selection was identified as a random sample of patients with FFPE available for HPV analysis, but were not selected by behavioral risk groups as men who have sex with men (MSM), a history of cancer of the cervix or vulva, immunosuppressed as HIV + or history of organ transplantation. Results: Median age 59 (31-80y); gender: F 35/52(65%). HIV+: 17% (9/52). HPV was detected in 84%(44/52) of which 80% had HPV16+. Multiple-serotype HPV infection was detected in 13% of the samples that included other high-risk serotypes 18, 33, 42, 44, 45, 52, 54, 72. Serotypes of low oncogenic risk as HPV6-11 were detected in 5% of the cases. We obtained follow up data from 42/52 cases treated in our institution. The initial treatment approach was Local Resection: 3 patients, Definitive CRT: MMC+5FU:17pts (5-FU 1000 mg/m2/d IV d1-4 and 29-32 mitomycin 10 mg/m2/d IV bolus d1)MMC+Cape: 3pts. (capecitabine 825 mg/m2 PO BID days 1-5 weeklymitomycin 12 mg/m2 IV bolus day 1), CDDP+5FU: 15pts. (5-FU 1000 mg/m2/d IV d1-4 and 29-32 CDDP 75 mg/m2/d IV bolus d1) and Palliative Care treatment 4 pts. Response assessment after CRT was Complete Response: 80% (28/35), Partial Response: 14% (6/35) and Disease Progression: 6% (2/35). In the subgroup of HPV+ patients, CR was observed in 82% (23/28). Median OS in complete responder was 54m (14-190m) and OS in non-complete responders was 18m (16-52m) p=0.003. Median Colostomy free survival in CR was 46m (14-190m). Conclusion: The HPV prevalence in our cohort is similar to that described in other regions. The serotype spectrum is limited with a remarkable predominance of HPV16 and a minority of multiple infections. The presence of HPV 6 and 11 reconfirms the transformative potential of these low risk viruses in the anus. There is still a certain lack of homogeneity in the response rate of HPV+, probably related to the immune response in the host. Collaborative efforts for these rare types of cancer are needed towards a broad comprehensive classification for both patient staging and improved treatment strategies.