ORAL CONTRACEPTIVE USE AND BREAST CANCER IN YOUNG WOMEN IN SWEDEN

Abstract

This letter reports the results of a case-control investigation of the relationship between oral contraceptive (OC) use and breast cancer in young women in southern Sweden. 80 consecutive cases of breast cancer in women born in 1939 or later and diagnosed at the age of 45 years or earlier were each matched to 3 healthy controls selected from the population registry. Logistic regression analyis indicated that women who began OC use at 20-24 years of age had 3 times the risk of developing breast cancer before 46 years of age as nonusers. The relative risk increased with earlier age of start of OC use. The risk was lower although not significantly so for women who started OC use after their 1st pregnancy. Increased breast cancer risk was further related to a low age at menarche and a high age at 1st fullterm pregnancy. These findings are consistent with earlier reports linking OC use and breast cancer; they will be reported more fully elsewhere.