Anal Cancer - Risk Factors

Risk Factors

• Human papillomavirus: Examination of squamous cell carcinoma tumor tissues from patients in Denmark and Sweden showed a high proportion of anal cancers to be positive for the types of HPV that are also associated with high risk of cervical cancer. In another study done, high-risk types of HPV, notably HPV-16, were detected in 84 percent of anal cancer specimens examined. Based on the study in Denmark and Sweden, Parkin estimated that 90% of Anal cancers are attributable to HPV.
• Sexual activity: Having multiple sex partners due to the increased risk of exposure to the HPV virus. Receptive anal intercourse, whether male or female, increases the chances of anal cancer sevenfold due to Human papillomavirus. Those who engage in anal intercourse with multiple partners are 17 times more likely to develop anal cancer than those who don't, if their insertive partners are infected with the HPV virus.
• Smoking: Current smokers are several times more likely to develop anal cancer compared with nonsmokers. Epidemiologist Janet Daling, Ph.D., a member of Fred Hutchinson's Public Health Sciences Division, and her team found that smoking appears to play a significant role in anal-cancer development that's independent of other behavioral risk factors, such as sexual activity. More than half of the anal-cancer patients studied were current smokers at the time of diagnosis, as compared to a smoking rate of about 23 percent among the controls. "Current smoking is a very important promoter of the disease," said Daling. "There's a fourfold increase in risk if you're a current smoker, regardless of whether you're male or female." They explained that the mechanism behind smoking and anal-cancer development is unknown, but researchers speculate that smoking interferes with a process called apoptosis, or programmed cell death, which helps rid the body of abnormal cells that could turn cancerous. Another possibility is that smoking suppresses the immune system, which can decrease the body's ability to clear persistent infection or abnormal cells.

• Immunosuppression, which is often associated with HIV infection.
• Benign anal lesions (inflammatory bowel disease (IBD), hemorrhoids, fistulae or cicatrices). Inflammation resulting from benign anal lesions, such as hemorrhoids and anal fistulas, has been considered to cause a predisposition to anal cancer.