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Lancet. 1983 Oct 22;2(8356):926-30.

Breast cancer in young women and use of oral contraceptives: possible modifying effect of formulation and age at use.

Abstract

A case-control study of 314 breast cancer patients aged less than 37 at diagnosis and 314 individually matched controls was done to assess the influence of oral-contraceptive (OC) use on the risk of the disease. Long-term use before age 25 of combination-type OCs with a "high" content of the progestogen component was associated with increased risk of breast cancer: the relative risk was approximately 4 after 5 years of such use, and 9 cases and no controls had used such combination-type OCs for more than 6 years before age 25. Use of combination-type OCs with a "low" progestogen component appears to increase breast-cancer risk little or not at all.

PIP:

A case control study of 314 breast cancer patients aged under 37 at diagnosis and 314 individually matched controls was done to assess the influence of oral contraceptive (OC) use on the risk of the disease. It was hypothesized that combination type OCs with high estrogen and high progesterone content as measured by uterine reaction would produce the greatest effect of breast tissue; combination OC use at very young ages would create the greater risk of breast cancer since it would increase the number of cycles with elevated hormonal levels among young women who might otherwise experience long and frequently anovular cycles. The patients were Los Angeles county white women with histologically confirmed breast cancer diagnosed between July 1972 and May 1982. The cases had used OCs for an average 49.6 months and controls for 39.2 months, with the difference most pronounced before age 23. The relative risk of breast cancer in relation to OC use before age 25 was 4.9 for 6 or more years of OC use, and the trend of increasing relative risk with longer durations of use was significant. All 8 combination OC formulations with progesterone potencies of 5 units or more were associated with excess use before age 25 in the cases; their use accounted for 86% of the difference in use between controls and cases. 9 cases, but no controls, had used such preparations for more than 6 years before age 25. Use of combination OCs with a low progestogen component appears to increase breast cancer risk little or not at all. These findings are not confirmed in previous studies of older OC users which report no association between breast cancer and OC use when other risk factors are controlled.

PMID:
6138501
[Indexed for MEDLINE]

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