Human papillomavirus (HPV) is the most common viral sexually transmitted infection (STI) in the world, and is the most common cause of anal cancer. The most common HPV types that cause cancer are types 16 and 18 and it may be useful to test for them. Anal cancer is a cancer of the anus which occurs when healthy cells in the area have become abnormal. These abnormal cells then proceed to grow and destroy healthy cells. HPV is the same virus that causes cancer of the cervix in women. HPV starts out as an infection that may not cause any changes in the tissues; at a later stage, there may be abnormal changes in the tissues (called dysplasia or pre-cancer); some dysplasia can progress to cancer. In HIV-positive MSM, the rates of anal HPV infection are very high and the rates of anal cancer are over 100 times the rate in the general population. Unfortunately, by the time men present with symptoms that suggest anal cancer, the cancer is often quite advanced and not easily treated. Thus, it is best to try to detect pre-cancerous changes so that anal cancer can be prevented.

Despite this evidence regarding anal cancer, there is no agreement on how best to detect and manage the anal pre-cancers in MSM. There are no routine screening programs or guidelines and there is no consensus on how best to diagnose these changes in the anus. There are only a handful of physicians in Canada trained to do detection and treatment of HPV-related pre-cancers in MSM.