Sexual behaviour and increased anal cancer.

An increase in epidermoid anal cancer has been observed in the past 30 years (1959-89). This increase in anal cancer has been noted to be more pronounced in women than men. The absence of a significant interactive effect of the HIV and human papillomaviruses and the incidence of anal cancer has been noted in some studies. These observations provide the rationale for consideration of other aetiologic agents that may contribute to the increase of anal cancer in men and women. Within the context of their ability to serve as cancer initiating and promoting factors, spermatozoa and seminal plasma are suggested as aetiologic agents and/or cofactors which are common to men and women practising anal intercourse in whom an increase in anal cancer has been observed. It is further suggested that sexual behaviour, that is, anal intercourse, not sexual preference, is one of the primary factors in the development of anal cancer.