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USC study finds no link between breast cancer, oral contraceptives

A new study from Keck School of Medicine researchers adds more evidence to a growing body of findings suggesting there is no association between oral contraceptive use and risk of breast cancer.

“Oral Contraceptive Use and Risk of Breast Carcinoma In Situ”, which appeared in a recent issue of Cancer Causes and Control, compared 567 women newly diagnosed with in situ breast cancer in Los Angeles County with 614 unaffected women who served as control subjects. They found oral contraceptive use was not associated with increased risk of breast cancer.

The study also found risk of in situ breast cancer did not increase with longer periods of oral contraceptive use and risk was not modified by age, race or the estrogen dose of pills.

“Although many studies have examined the impact of oral contraceptives on risk of invasive breast cancer, very few have assessed whether they are associated with risk of in situ breast cancer,” said Leslie Bernstein, professor of preventive medicine and co-author of the study. In situ breast cancer is breast cancer confined to the milk ducts or lobules and has not invaded surrounding breast tissue.

Recent estimates show that more than 80 percent of sexually active women in the U.S. between the ages of 18 and 44 have used oral contraceptives at some time in their lives. Because the contraceptives contain estrogen, which can affect breast cell growth and development, “researchers are very interested in a possible link between oral contraceptive use and breast cancer risk,” said Bernstein.

“Our results are consistent with those of recent studies of invasive breast cancer and two prior studies of in situ breast cancer, confirming the lack of any increase in breast cancer risk,” she said. Efforts are now underway to combine studies of in situ breast cancer, to allow more detailed assessment of subgroups of women and to permit the assessment of predictors of recurrence or progression to invasive breast cancer.

The study was supported by funding from the Department of Defense U.S. Army Medical Research and Materiel Command, the National Institute of Child Health and Human Development, the National Cancer Institute and the California Department of Health Services.

Jasmeet K. Gill, Michael F. Press, Alpa V. Patel, Leslie Bernstein, “Oral Contraceptive Use and Risk Of Breast Carcinoma In Situ (United States)”, Cancer Causes and Control 2006, Volume 17, pages 1155-1162.

USC study finds no link between breast cancer, oral contraceptives

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