What's the Evidence?
The anus has cells that can become infected with human papilloma virus (HPV) which causes changes to those cells and can lead to cancer, similar to how HPV can lead to cervical cancer. "No one knew that cervical cancer was preventable before the use of Pap smears became widespread in the 1960s and cut the incidence of the disease by 80 percent.
What Data is Still Missing?
Screening for anal cancer is not routine like screening for cervical or colon cancer. Although Pap smears and removal of cells damaged by HPV has been proven to prevent cervical cancer, we don’t know whether a similar approach can prevent anal cancer. We think that anal cancer can be prevented by routine screening and removal of precancerous cells.
This strategy has reduced cervical cancer rates by 80%. But to get the insurance companies to cover routine anal cancer screening and preventative treatment, we need to prove that this strategy actually prevents cancer.
The best way to show that is to recruit people with High Grade Squamous Intraepithelial Lesions (or HSIL for short) into a study and assign them randomly to a treatment arm or a monitoring arm. We then follow everyone for five years to compare the rates of cancer in both study arms. At the end of the study we’ll know whether screening and treatment of HSIL are effective strategies in preventing anal cancer. We’ll also learn a lot about HPV and other risk factors and why these sometimes cause cancer.