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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.
People. 1984; 11(1):33.Recent suggestions that there might be a causal link between oral contraceptives (OCs) and breast and cervical cancer are not based on evidence strong enough to warrant any change in prescribing practice, according to the medical advisers of the International Planned Parenthood Federation (IPPF). A US study suggests that for women who use OCs for several years before the age of 25 there may be a slightly increased risk of developing breast cancer later in their lives. The risk of breast cancer was influenced by the type of OCs the women took. They suggest that those brands with a high level of progestogen potency are the culprits. The other study from the UK suggests that women who use OCs for several years are more likely to develop cancer of the uterine cervix than women who use IUDs for similar lengths of time. Both studies left the Medical Advisory Panel of IPPF convinced that there is insufficient evidence to make it advisable for family planning programs to change their prescribing policies. The breast cancer study has several methodological weaknesses which could have influenced its results and these differed from results published by other, large scale studies. There is strong disagreement in the medical profession about the validity of the way the US team assessed progestogen potency. The Panel agreed that the number of women in the study who used each brand of OC was too small to justify drawing any definite conclusions about which OCs to prescribe for women aged under 25. The Panel noted that the cervical cancer study failed to take into account the sexual history of the subjects even though the age at 1st intercourse and the number of sexual partners a woman has are known to affect the likelihood of her developing cervical cancer. This, combined with the fact that other studies have not shown a relationship between OC use and cervical cancer, led the Panel to recommend to change in current practice. Data from the 2 studies are currently being analyzed again, to look specifically at the association between breast cancer and OC use. This reanalysis will be closely monitored by the Panel which will review its own recommendations as further evidence becomes available.