To the Editor.
—Dr Hankinson and colleagues1 recently reported a strong inverse association between tubal ligation and ovarian cancer, with a weaker inverse association between simple hysterectomy and ovarian cancer, using the Nurses' Health Study cohort, thereby confirming previous observations in retrospective studies.2,3 Weiss and Harlow4 had previously suggested that the observed protective effect of prior pelvic surgery might result from examination of the ovaries at the time of surgery, with subsequent removal of abnormal ovaries; in this way, asymptomatic malignant or premalignant ovaries would have been selectively removed from the surgery group, falsely reducing the true relative risk. Hankinson et al attempted to minimize the potential for this detection bias in two ways: by requiring a minimum 4-year interval from the time of tubal ligation to the beginning of the defined risk period, and by examining medical records to determine how many ovarian cancers were detected
Myers ER. Tubal Ligation, Hysterectomy, and Risk of Ovarian Cancer. JAMA. 1994;271(16):1235. doi:10.1001/jama.1994.03510400021010