Breast cancer and oral contraceptives: critique of the proposition that high potency progestogen products confer excess risk.

A recent report by Pike et al. from the U. S. A. concluded on the basis of epidemiologic evidence that an increased risk of breast cancer was manifested by young women who had used combination oral contraceptives (OC) with a high "potency" of progestogen over a prolonged period. This conclusion is criticized in the present article, centering on three cardinal defects in the Pike study: (1) The assigned potencies of OC's are fiction and were derived from out-dated delay-of-menses data; (2) Well-known risk factors for breast cancer were ignored; (3) The method assumed no error of recall of OC brand, dose and duration of use occurring many years before telephone interviews. Noting that others have not been able to confirm these findings, it is concluded that there is no scientific basis for accepting the suggestion of Pike et al.