Changes In The Incidence Of Anal Cancer Cases In Canada: From 1971 To 2010 A Population Based Study

Joseph NIYIBIZI, University of Montreal, Canada

1 Department of Social and Preventive Medicine, Sainte Justine Hospital Research Center, Montreal, Quebec, Canada
2 Department of Obstetrics and Gynecology, Faculty of Medicine Memorial University, St John's, Newfoundland, Canada
3 Public Health Agency of Canada, Ottawa, Ontario, Canada
4 Merck Canada, Montreal, Quebec, Canada

Purpose: Assess the change in incidence in men and women of HPV-related anal cancer in Canada and evaluate temporal and age specific trends.
Methods: National incidence data for HPV-related anal cancer were obtained from the Canadian Cancer Registry from January 1st, 1971 to December 31st, 2010. Age standardized incidence rates (ASR) per 100,000 person years were calculated. Trends in ASR were analyzed using the Joinpoint Regression Program. Average Annual Percentage Change (AAPC) was used to summarize trend changes over this period, rejecting the null hypothesis that AAPC equals 0 if the resulting p-value was <0.05.
Results: From 1971 to 2010, the ASR for anal cancer per 100,000 increased from 0.3 to 1.2 for males and from 0.5 to 2.3 for females. The AAPC for anal cancer was 4.3 (95% CI 2.7-5.6) p=0 and 3.8 (95% CI 3.0-4.6) p=0, in men and women respectively. The greatest ASR increase occurred prior to 1981 with a significant AAPC of 14.1 in men and 12.3 in women. In both men and women, nearly a quarter of overall anal cancer cases (27.9% and 23.1% respectively) were diagnosed between 65 and 74 years old. The peak ASR in men (2.2) occurred in the 65-74 age group between 1996 and 2000; and in women (2.9), in the 55-64 age group over the 2006-2010 period.
Conclusions: Anal cancer has increased over 40 years. There is no population based screening for this cancer. With HPV vaccination, incidence is expected to decrease by the next generation.
Funding source: None