Stephen J.LurieMD, PhD, Senior EditorIndividualAuthor
To the Editor: Ms Grabrick and colleagues1 suggest that the risk of breast cancer from oral contraceptive (OC) use is related to estrogen use. They state, "The amount of estrogen in OCs has decreased from an initial 150 µg to 50 µg or less currently. . . ." However, the original 1960s "pill," Enovid, contained many times that amount of estrogen. I can find no studies on the risk of breast cancer from Enovid use. If the risk is in fact dose-related, that would seem an obvious "natural experiment."
Kirkland LR. Oral Contraceptives and Risk of Breast Cancer in Women With a Family History of Breast Cancer. JAMA. 2001;285(1):39-40. doi:10.1001/jama.285.1.39