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.

The evolution of HPV-related anogenital cancers reported in Quebec - incidence rates and survival probabilities.

Non-cervical anogenital cancers (i.e. anal, vulvar, vaginal and penile cancers) associated with the human papillomavirus (HPV), for which HPV is known to be the necessary cause of carcinogenesis, are poorly documented due to their relatively low incidence rate. The aim of this study is to describe the incidence rates of these cancers between 1984 and 2001, and their relative survival probabilities, in Quebec (Canada) between 1984 and 1998. The incidence of these cancers is on the rise, particularly anal cancer in women and, more recently (since 1993-95), vulvar cancer. Between 1984-86 and 1993-95, the 5-year relative survival probability for men with anal cancer decreased from 57% to 46%, while that for penile cancer dropped from 75% to 59%. However, during the same period, the 5-year relative survival probability for women with anal cancer rose from 56% to 65%, and remained stable for cervical and vulvar cancers, at 74% and 82%, respectively.

Sources of nitrate exposure in residents of rural areas in Quebec, Canada.

Nitrate exposure was investigated in a group of 187 people using well water and living in four areas of rural Quebec (Canada) with intensive agricultural activities. Nitrate intake was evaluated using a 24-h dietary recall and a food frequency questionnaire, in conjunction with a validated food database and measurements of nitrate concentrations in private wells. The total internal dose was estimated by means of the 24-h urinary nitrate excretion, while taking into account risk factors for endogenous nitrate formation. Mean (geometric) 24-h urinary nitrate excretion was 16.9 mg N for the 100 people with low groundwater contamination (mean nitrate concentration=0.18 mg N/l) and 23.3 mg N in the 87 individuals with moderate groundwater contamination (mean nitrate concentration=7.1 mg N/l). A multivariate analysis revealed that dietary nitrate intake during the last 24 h was the principal source of exposure, followed by water intake during the last 24 h. The Quetelet index was also a significant predictor of urinary excretion. The total predictive model explained only 29% of the variability in urinary nitrate excretion (R2=0.286). Neither the inflammatory status as indicated by elevated C reactive protein, the presence of Helicobacter pylori antibodies nor the occurrence of diarrhea during the last 24 h prior to urine collection were associated with urinary nitrate excretion. In conclusion, food and to a lesser extent water contribute to nitrate exposure in this rural setting with moderate water contamination. Better predictors of endogenous nitrate production are needed to improve our ability to model nitrate body burden and estimate associated health risks.