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Study Finds Higher Breast Cancer Risk For Women Who Took Older Versions of Oral Contraceptives (dateline October 13, 2000)

A new study finds that women with a family history of breast cancer who took oral contraceptives prior to or during 1975 are at a higher risk for breast cancer than women with similar family histories of breast cancer who did not take the older versions of birth control pills. The link between breast cancer and oral contraceptives was strongest among women with five or more cases of breast or ovarian cancer in their families. According to researcher Thomas Sellers, PhD, there is no currently evidence that oral contraceptives on the market after 1975 increase breast cancer risk.

"These results suggest that women who have ever used earlier formulations of oral contraceptives and who also have a first-degree relative with breast cancer may be at particularly high risk for breast cancer," wrote the researchers. The study appears in the October 11, 2000 issue of the Journal of the American Medical Association.

In the study, researchers studied multiple generations of 426 families with members who had been diagnosed with breast cancer between 1944 and 1952. The results of the study show that sisters and daughters of these women were more likely to develop breast cancer if they took oral contraceptives before or during 1975 compared with women who did not take oral contraceptives. The risk of breast cancer was highest among women with several cases of breast or ovarian cancer in their families.

Oral contraceptives made after 1975 contain lower levels of estrogen and progestin and were not associated with increased breast cancer risk in the study. According to the researchers, further studies are needed to determine whether women with a strong family history of breast cancer should avoid oral contraceptives today.

Though the study does find a significant link between earlier forms oral contraceptives and breast cancer risk, the results leave many unanswered questions. According to Wylie Burke, MD, PhD, the study does not indicate whether any or all of the women with a family history of breast cancer also carried genetic risk factors for the disease. Studies have shown that women who have genetic mutations of BRCA1 (breast cancer gene 1) and BRCA2 (breast cancer gene 2) are at significantly higher risk of breast and ovarian cancer.

How Does the Study Affect Women Who Use (or Have Used) Oral Contraceptives?

The results of the study do indicate that women who took oral contraceptives before or during 1975 should be aware that they may be at higher risk for breast cancer and should discuss this issue with their physicians. Women 40 years of age and older should receive annual mammograms, annual clinical breast exams, and perform monthly breast self-exams.  In addition, some of the women who took older versions of oral contraceptives may be candidates for the drug tamoxifen, which has been shown to help reduce the risk of breast cancer. However, according to Dr. Burke, the effectiveness of tamoxifen in women with BRCA gene mutations is still unknown.

Preventive breast removal (called prophylactic mastectomy) is another option for women at very high risk of breast cancer. Prophylactic mastectomy has been shown to reduce the risk of breast cancer by 90% in women at high risk for the disease. While preventive breast removal may increase life expectancy in women with aggressive tumors, some women with a strong family history will never develop breast cancer and would not benefit from a prophylactic mastectomy. Also, if breast cancer is detected early, less invasive procedures such as lumpectomies can often be performed without having to remove the entire breast(s).

The study did not find an increased risk for breast cancer among women who took oral contraceptives after 1975. Most oral contraceptives prescribed after 1975 contain less than 50 micrograms of estrogen (50% to 100% less estrogen than most birth control pills contained before 1975).

According to Dr. Burke, "the use of oral contraceptives needs to be considered on an individual basis, taking into account baseline risk for breast and ovarian cancer, alternative strategies for cancer risk reduction, and other benefits oral contraceptives may provide." Several studies have shown that oral contraceptives significantly reduce the risk of ovarian cancer, especially if taken for more than five years. Because there may be no obvious symptoms associated with early stages of ovarian cancer, many cases are diagnosed in advanced stages, when survival is much lower.

Future studies will help determine whether women with a very strong risk of family history should avoid oral contraceptives and whether the risk associated with oral contraceptives is reduced after a woman stops taking "the Pill."

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