Abstract

PIP: As more epidemiological studies are done on the effect of oral contraceptives (OCs) on breast cancer, the more unclear the effects are. On the other hand, 9 case control studies demonstrated that combined OCs reduce the risk of endometrial cancer, and 8 case control studies showed a reduced risk of ovarian cancer. It is biologically plausible for there to be a protective effect against these 3 cancers, but as for breast cancer, it is not yet known if combined OCs enhance or antagonize harmful effects of ovarian activity. Researchers conducted a case control study in 11 areas of the United Kingdom consisting of 755 women with breast cancer that had been diagnosed before the age of 36 years. They found an association between the duration of use of combined OCs and the risk of breast cancer (relative risk of 1.74) after 8 years of using combined OCs. The significance of this study was that the association was noted whatever the age at which the combined OCs were taken and was noted both before and after the 1st full term pregnancy. Another new finding included an apparent link between cancer risk and the dose of estrogen: those combined OCs with 50 ug ethinyl-estradiol carried less of a risk, yet some risk was still detectable with low dose pills. Since the researchers restricted the study to women 36 years old, the results may not be relevant to most women with breast cancer, however. Further, the authors of this study bring to the reader's attention that the national breast cancer registration rates are not increasing. This is indeed reassuring.