Oral Contraceptives and Benign Ovarian Tumors

(We’ve known for some time that antecedent use of oral contraceptives during the reproductive-age years reduces the risk of ovarian cancer after menopause. However, whether there is a parallel effect on benign ovarian tumors has not been answered definitively. Most studies of the “nonendometriosis” benign tumors, such as serous cystadenoma, mucinous cystadenoma, teratoma, Brenner tumor, and fibroma-thecoma, have had relatively small numbers of patients and have not demonstrated marked effects of oral contraceptives, either beneficial or detrimental. Actually, the present study also does not demonstrate dramatic decreases in the prevalence of these types of tumors in women taking oral contraceptives. Even when endometriosis was included with the other benign tumors, the use of oral contraceptives was associated, at best, with a modest decrease in the risk (odds ratio = 0.79, 95% confidence interval = 0.60–1.05). There was no suggestion of reduced risk for short-term (1–24 months) current users, but for current users who used oral contraceptives for a longer period, there was the suggestion of a reduced risk. There was a strong trend of decreasing risk with duration of use for all types of tumor, and this trend seemed to be due to the decreased risk for women with endometriosis or endometriomas. Similar to the findings for current use, when duration of use was evaluated as a continuous variable in months, the trend toward decreasing risk with increasing oral contraceptive use essentially was limited to women with endometriomas. It isn’t too surprising that the impact of oral contraceptive use was seen primarily in women with “endometriomas.” Actually, the authors lumped together patients with endometriosis and patients with endometriomas and referred to the entire group as the “endometrioma” group. Endometriosis is the most hormone-dependent of the disorders of the ovary investigated in the present study and thus most likely to be affected by hormonal therapy. The authors note that previous studies have found a negative association in endometriosis with current users only (MP Vessey et al., BMJ 1993;306:182; F Parazzini et al., Contraception 1994;49:47) and that the authors of those studies concluded that oral contraceptive use does not offer long-term protection against endometriosis. In contrast, in the present, larger, study, a decreased risk of endometriosis/endometriomas for both current and past oral contraceptive users as well as a decreasing risk with increased duration of use were observed. This didn’t surprise me, because improvement often continues to occur in patients who receive gonadotropin-releasing hormone (GnRH) analogs for treatment of endometriosis after the GnRH analog is discontinued (unlike in women with leiomyomas, which resume their former size quite rapidly after the GnRH analog is stopped.) Thus, oral contraceptive use was associated with a modest, long-lasting decreased risk of the lesions studied in this investigation, mostly in the endometriosis/endometrioma group, which was the largest group of patients. These findings held for both low- and high-estrogen-dose oral contraceptives, which is also not surprising because even low-dose preparations inhibit gonadotropins and therefore ovarian stimulation.—RBJ)