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Pill studies: more data needed.

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.

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