NEW YORK (Reuters Health) - Although birth control pills have been weakly linked to breast cancer in some studies, a new study conducted by researchers at the US Centers for Disease Control and Prevention (CDC) has found that past use of such pills does not increase a woman's risk of developing breast cancer.

The study, which also found that current birth control pill users between the ages of 35 and 64 years are also not at significantly increased risk of developing breast cancer, was published in the June 27th issue of The New England Journal of Medicine.

The large study should "reassure the millions of women who have taken, or are currently taking, oral contraceptives," the study's lead investigator, Dr. Polly A. Marchbanks of the CDC in Atlanta, Georgia, told Reuters Health.

About 80% of women in the US born since 1945 have used oral contraceptives, according to Marchbanks, who interviewed 4,575 women who had been diagnosed with breast cancer and 4,682 women who did not have the disease. All of the women answered questions about oral contraceptive use, reproductive history, overall health and family history of diseases.

"The study provides strong evidence that past use of oral contraceptives does not increase the risk of breast cancer later in life," Marchbanks told Reuters Health in an interview.

And women between the ages of 35 and 65 who are "currently using (oral contraceptives) are not at significantly increased risk," she added. However, the findings were less conclusive for those between the ages of 45 and 64.

In other findings, Marchbanks said that women with a family history of breast cancer who took oral contraceptives were not at increased risk of developing the disease, nor were women who started taking birth control pills at an early age.

What's more, the risk of developing breast cancer did not increase the longer a woman used oral contraceptives or with higher doses of estrogen. The results were similar among white and black women, the report indicates.

"The study...provides further reassurance that oral contraceptives use, even for a long period, is not associated with an increased risk of breast cancer," write Drs. Nancy E. Davidson and Kathy J. Helzlsouer of Johns Hopkins University in Baltimore, Maryland in an accompanying editorial.

SOURCE: The New England Journal of Medicine 2002,346:2025-2032, 2078-

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