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Breast cancer, cervical cancer, and depot medroxyprogesterone acetate. [WHO Collaborative Study of Neoplasia and Steroid Contraceptives] [letter].
Lancet. 1984 Nov 24; 2(8413):1207-8.This letter presents the preliminary findings of a collaborative, multinational, hospital-based, case-control study being conducted under the auspices of the World Health Organization to assess the influence of depot medroxyprogesterone acetate (DMPA) on risks of mammary, gynecological, and hepatobiliary malignancies. The frequency of ever-use of DMPA was greater in breast cancer cases (15/246, or 6,0%) than in controls (381/4162, or 9.2%). When adjusted for age, center, age of birth of 1st child, and nulliparity, the relative risk in women who had ever used DMPA was 0.7. The lowest risk was noted in women who had used DMPA for 3 or more years, but no decreasing trend in risk with duration of use was evident. The reducton in risk of breast cancer in DMPA users was largely confined to women with 1st exposure after age 30 years. In terms of cervical cancer, a history of DMPA use was reported by slightly more cases (67/469, or 14.3%) than controls (269/2704, or 9.9%). Use of oral contraceptives, number of cervical smears, and number of pregnancies were the variables most strongly related to cervical or having the greatest influence on relative risk estimates for users of DMPA. When controlled for these 4 factors and age and center, the relative risk in DMPA was 1.13. The highest relative risk was found in longterm users, although there was no clear trend of increasing risk with duration of DMPA use. These preliminary findings provide no evidence that DMPA increases the risk of breast cancer. The relative risk for cervical cancer for DMPA users obtained in this study could be due to chance or to incomplete control for the confounding effect of sexual variables. Although the absence of a trend of increasing risk with duration of use tends to rule out a causal connection between DMPA use and cervical cancer, the doubling of risk in women who used DMPA for 5 years or more is of potential concern.