Objective — The oncogenic HPV subtypes responsible for gynecologic malignancies have also been implicated in the development of squamous cell cancer of the anus (SCAC). SCAC is more common in women, typically presenting at an older age than gynecologic cancers. The aim of this study was determine whether women diagnosed with anal cancer are more likely to have a history of HPV-related gynecological cancer as compared to a matched control group.
Methods — We performed a population-based, case-control study at the Institute for Clinical Evaluative Sciences (ICES) which houses the administrative databases for all residents of the province of Ontario, Canada. All women diagnosed with SCAC between 1992 and 2005, identified using ICD-9 codes (154.2, 154.3, 154.8) for anatomic site and ICD-O codes (8070–8075, 8120, 8123, 8124) for histologic subtype, were included as cases. Up to 5 female controls, matched for age, socioeconomic status, health region and number of years enrolled in the provincial health plan, were selected for each case. The exposure of interest was previous HPV-related gynecologic cancer, specifically cervical cancer, vulvar cancer and vaginal cancer. Conditional logistic regression was performed to assess the relationship between this exposure and SCAC.
Results — A total of 674 women with SCAC were identified whose median age was 61. Amongst the cases, there were 7 cervical, 3 vulvar and 1 vaginal cancers compared with 5 cervical, 0 vulvar and vaginal cancers in the 3264 controls. Previous HPV-related gynecological cancer (cervical, vaginal or vulvar cancer) was significantly associated with SCAC (OR: 10.5, 95% C.I.: 3.6 to 30.3). The median time between the diagnosis of anal cancer and previous cervical cancer was 20 years.
Conclusions — Previous HPV-related gynecological cancers are strongly associated with anal cancer and may occur decades before the anal cancer.