Anal cancer incidence among women with a history of vulvar cancer by histology, age, and time since diagnosis.

Women with a history of vulvar cancer face a high risk of anal cancer; however, incidence according to histology, age-at, and time since vulvar cancer diagnosis remains unexplored. Using data from SEER-8 and SEER-17 registries, we identified 21,230 women with vulvar cancer, with 154,825 person-years follow-up from 1975 to 2021. We observed 95 anal cancer cases, resulting in an incidence of 61.4 per 100,000 person-years (95% CI, 49.6-75.0). Incidence was higher among women with vulvar squamous cell carcinoma (SCC) (78.7; 95% CI, 62.9-97.1) than vulvar non-SCC (19.8; 95% CI, 9.0-37.6). The highest incidence (>100 per 100,000) was observed in women <45 years old with vulvar SCC and those >10 years post-diagnosis. These findings could inform anal cancer screening guidelines, as women with vulvar cancer, particularly those diagnosed with SCC, may substantially benefit from heightened surveillance or targeted screening.