Etiologic fraction of HPV-attributed anal and penile squamous cell carcinoma: study in specialized hospitals, Sri Lanka

Introduction The Human Papilloma Virus (HPV) infection is known to cause anogenital cancers. Male HPV prevalence and population-attributable risk (PAR)are important to plan future HPV preventive strategies for HPV-driven anogenital cancers in males. Methods A hospital-based case-control study was carried out to determine the etiologic fraction attributed to HPV-driven anal and penile(anogenital) cancers among male patients presenting to tertiary care hospitals in Gampaha district and Apeksha Hospital (cancer specialized), Sri Lanka and to calculate PAR percentage on anogenital SCC among the study population where HPV prevalence was 5.7%. New or already diagnosed patients for anal and penile SCC who reported to selected hospitals from August 2022 to June 2023 were recruited for data and specimen collection. A sample size of 20 cases and 80 controls were selected, with four controls chosen per case from sexually active, clinically normal men aged 20-70 years residing in the Gampaha district. Additional etiological factors that were checked included the presence of sexually transmitted infections, phimosis, anogenital injury, and the use of tobacco, alcohol or illegal drugs. The chi-square test was used at the level p<0.05 significance. Bivariable and logistic regression analyses were used to calculate odds ratios (ORs). Results A significantly associated factor for getting anal and penile SCC was HPV infection (p<0.001; adjusted OR: 27.7; 95% CI: 4.3,177.8).For any HPV genotype & high-risk HPV genotype, prevalence was 55% & 50% among cases and 5% & 2.5% among controls respectively. Assuming prevalence among controls as the population prevalence, the calculated PAR% was 62.2% for any HPV genotype and 33% for the HPV 16 HR genotype. Conclusions Sixty-two per cent of the anal and penile SCCs were attributed to any HPV genotype and one-third of anal and penile SCCs can be prevented by introducing HPV 16 genotype-containing vaccine to male.