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CONTRACEPTIVE TECHNOLOGY UPDATE. 1992 Jan; 13(1):15-6.A recent World Health Organization (WHO) study found that women using Depo-Provera have only a slight increased risk of breast cancer. WHO examined case-control data from 5 hospitals in Africa, Mexico, and Thailand. The study revealed a 1.21 relative risk of breast cancer among all women in the study who had used Depo-Provera (a relative risk of 1.0 means that there is neither an increased or decreased likelihood to develop the disease in question). A relative risk of 1.21 indicates that there is a 21% increased likelihood of developing the disease, but any relative risk of less than 2.0 is considered slight. The study also found that among the diagnosed breast cancer cases, 12.5% had ever used Depo-Provera, compared to 12.2% among the control patients. Although an increased risk of breast cancer among women--especially women under 35--within the first 4 years of exposure to Depo-Provera was found, the risk did not increase with the duration of use, and it did not increase among women who had used the drug for more than 5 years. WHO explains that the risk of breast cancer among Depo-Provera user is similar to that found among oral contraceptives users, whose relative risk ranges from 1.0-1.42. Based on their findings, WHO investigators estimate that there would be 7-8 new cases of breast cancer per 100,000 Depo-Provera users annually, compared to 5 new cases annually among women who had not used the drug. As a recent commentary by Family Health International (FHI) points out, this increased risk of breast cancer must be weighted against the benefits provided by Depo-Provera. FHI concludes that there is a net gain for women using Depo-Provera, since despite the slight risk of breast cancer, it would result in a higher life expectancy compared to women not using contraception.
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.