Trends in anal cancer in Australia, 1982-2005

Most anal squamous cell carcinomas (SCCs) are caused by high risk types of human papillomavirus (HPV) and are potentially preventable by HPV vaccination. In order to understand the burden of potentially preventable anal cancer in Australia, we examine the incidence and survival from invasive anal SCC 1982-2005.

We reviewed data on invasive anal cancer cases notified to the National Cancer Statistics Clearing House. Age specific incidence rates of SCC were calculated by year of cancer diagnosis and by birth cohort, and rates of anal adenocarcinoma were included for comparison. Incidence rates were age standardised to the Australian 2001 standard population. Trends in relative survival of SCC were examined.

During the study period, a total of 4615 invasive anal cancer cases were diagnosed and most (69.7%) were SCC. Annual incidence of SCC increased almost 50%, from 0.65 to 1.00/100,000. Incidence increased at all ages. The annual rate of increase was almost two-folder higher in men (3.42%, 95% CI 2.49-4.35) than in women (1.88%, 95% CI 1.18-2.58). Five-year relative survival increased by nearly 10% from 58.9% to 68.3% over the last 20 years. Younger patients and women had better survival. For anal adenocarcinoma, increases of borderline significance were seen in men and women.

There is an increasing burden of anal SCC in Australia. The group with the highest incidence - homosexual men - are not likely to be protected under the current vaccination policy.