Although anal cancers in women are rarer than cervical cancers, anal HPV infections appear more common. Cumulative incidence of anal HPV reaches 70% over a 3 year period of time in young women. The true prevalence of anal HPV infection is unknown since sampling for anal HPV is usually contaminated by passing a swab through the perianal area. Hygiene habits (wiping front to back) may also result in anal sample contamination or a source of infection.
Literature was reviewed.
As seen in the cervix, the majority of anal HPV infections clear within 3 years. HPV 16 appears to clear slower than the other hrHPV types which may explain its prominent role in anal cancer. Factors associated with anal HPV persistence include concomitant cervical HPV infection, alcohol use, smoking, anal finger sex, recent anal intercourse and no condom use during anal or vaginal intercourse.
Repeated anal HPV infections are extremely common. In one study, only one third of women were HPV-free after 3 years of observation. These anal HPV infections are not all benign. Although the data is sparse for general healthy populations, abnormal anal cytology occurs in approximately 4-6% of healthy women. The majority of lesions detected are benign (LSIL). Anal HSIL confirmed by histology is quite low--<1%. Risk factors for anal SIL appear similar to that of the cervix and include number of sex partners, reporting anal sex, smoking, history of abnormal cervical cytology and anal HPV infection.
The natural history of these lesions in healthy women is completely unknown. Progression in MSM has been estimated at 3% per year—if this translates to women who do not practice anal intercourse regularly or at all is questionable.
Although anal cancers occur more often in immunosuppressed women (i.e. HIV infected, solid organ transplants and those with autoimmune disease), the majority of anal cancers occur in women with no known immunodeficiency. There are no recommendations for anal cancer screening in general healthy populations. Screening is only recommended if symptoms of anal cancer are present.