Trends in Risks for Second Primary Cancers Associated With Index Human Papillomavirus–Associated Cancers

IMPORTANCE: In the last 4 decades, survival among patients with human papillomavirus (HPV)–associated cancers has improved, while the incidence of these cancers has increased among younger cohorts. Among survivors of HPV-associated cancers, persistent HPV infection may remain a risk factor for preventable HPV-associated second primary cancers (HPV-SPCs). OBJECTIVES: To investigate the risk of HPV-SPCs among survivors of HPV-associated index cancers and to test the hypothesis that the HPV-SPC risk among these persons has increased over the last 4 decades. DESIGN, SETTING, AND PARTICIPANTS: A retrospective cohort study of 9 cancer registries of the Surveillance, Epidemiology, and End Results (SEER) database was conducted to identify patients with HPV-associated (cervical, vaginal, vulvar, oropharyngeal, anal, and penile) cancers diagnosed from January 1, 1973, through December 31, 2014. The dates of analysis were July 1, 2017, to January 31, 2018. MAIN OUTCOMES AND MEASURES: The HPV-SPC risk was quantified by calculating standard incidence ratios (SIRs) and excess absolute risks (EARs) per 10 000 person-years at risk (PYR). The HPV-SPC risk by time was estimated using Poisson regression. RESULTS: From 113 272 (73 085 female and 40 187 male) survivors of HPV-associated cancers, 1397 women and 1098 men developed HPV-SPCs. The SIRs for HPV-SPCs were 6.2 (95% CI, 5.9-6.6) among women and 15.8 (95% CI, 14.9-16.8) among men. The EARs were 18.2 per 10 000 PYR for women and 53.5 per 10 000 PYR for men. Among both women and men, those who had index oropharyngeal cancers had the highest HPV-SPC risk (SIR, 19.8 [95% CI, 18.4-21.4] and EAR, 80.6 per 10 000 PYR among women; SIR, 18.0 [95% CI, 16.9-19.1] and EAR, 61.5 per 10 000 PYR among men). Women who had index cervical cancers and men who had index anal cancers had the lowest HPV-SPC risk (SIR, 2.4 [95% CI, 2.2-2.7] and EAR, 4.5 per 10 000 PYR among women; SIR, 6.5 [95% CI, 4.7-8.8] and EAR, 18.5 per 10 000 PYR among men). Both women and men who had index HPV-associated cancers of any kind had a significantly higher risk of oropharyngeal HPV-SPCs. Over the last 4 decades, the risk of developing most types of HPV-SPCs after index cervical, vaginal, and vulvar cancers increased. CONCLUSIONS AND RELEVANCE: According to this study, the HPV-SPC risk among survivors of HPV-associated cancers is significant, implying that persistent HPV infection at multiple sites may be associated with HPV-SPCs. These findings have the potential to inform surveillance recommendations for survivors of HPV-associated cancers.