Squamous anal cancer: patient characteristics and HPV type distribution
BACKGROUND: Infection with high risk human papillomavirus (HPV) is strongly associated with anal cancer. However, detailed studies on HPV type distribution by gender and age are limited. METHODS: Retrospective study of 606 invasive anal cancers diagnosed between 1990 and 2005 in two large urban areas of the province of Québec, Canada. Cases were identified from hospitalization registry. Patient characteristics were collected from medical files. Archived anal squamous cancer specimens were available from 96 patients and were tested for HPV DNA and typing. Variant analysis was performed on 16 consecutive and 24 non-consecutive HPV16-positive samples to assess potential contamination during amplification. RESULTS: Among the 606 patients with anal cancers, 366 (60%) were women. Median age at diagnosis was 63 years. HPV was detected in 88/96 (92%) of cases. HPV16 was the most frequent type detected in 90% of HPV-positive specimens. Other types including 6, 11, 18, 33, 52, 53, 56, 58, 62 and 82 were also found. HPV 97 was not detected. HPV prevalence was associated with female gender and younger age. No contamination occurred during amplification as shown by the subset of 41 HPV16-positive samples, as 37, 2 and 1 isolates were from the European, African and Asian lineages, respectively. The most frequent variants were G1 (n=22) and the prototype (n=12). CONCLUSIONS: Women with anal cancer are at higher risk for anal HPV infection, and HPV infection, especially HPV16, is strongly associated with squamous anal cancer. Therefore, HPV vaccine could potentially prevent the occurrence of anal cancer in both men and women.