Melbye M: Tobacco smoking as a risk factor in anal carcinoma: an antiestrogenic mechanism? J Natl Cancer Inst

associated anogenital carcinogenesis depends on poorly defined cofactors. Smoking was recently suggested to in-crease the risk of anal cancer more in premenopausal women than in post-menopausal women. Thus, we used our population-based anal cancer case– control study in Denmark and Sweden to test this hypothesis. Methods: Our study included 417 patients (324 women and 93 men) who were diag-nosed with anal cancer (84 % invasive cancer) from 1991 through 1994; it also included five patients diagnosed in 1995. Two control groups were used: 1