what causes anal cancer

Anal cancer is primarily caused by infection with the human papillomavirus (HPV), especially high-risk strains like HPV-16. This virus is linked to about 90% of anal cancer cases. HPV causes changes in the cells of the anus that can lead to cancer by interfering with tumor suppressor proteins in the cells, allowing abnormal growth. Other risk factors that increase the chance of developing anal cancer include having anal sex, a higher number of sexual partners, smoking, being older (over 75), having a weakened immune system (such as from HIV or organ transplant), and having a history of cervical, vaginal, or vulvar cancer. Despite the strong link with HPV, most people infected with HPV do not develop anal cancer. Preventative measures such as HPV vaccination, practicing safe sex, quitting smoking, and maintaining a healthy immune system can help reduce the risk.