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Oral contraceptives and breast cancer risk

Researchers continue to unravel the web concerning the use of oral contraceptives and the risk of breast cancer. A study published in June 2002 indicated that birth control pills don't increase the risk of breast cancer for women in the general population (see August update). But a new study published in the December 4, 2002, issue of the Journal of the National Cancer Institute shows oral contraceptives can increase the risk of breast cancer in women with a particular genetic mutation.

The study examined whether the use of oral contraceptives increased the risk of breast cancer in women with a mutation in the BRCA1 or BRCA2 gene. Women who have such a mutation are already known to have a high risk of developing breast cancer and ovarian cancer. A person inherits these types of gene mutations.

The study involved 1,311 pairs of women who have the BRCA1 mutation, BRCA2 mutation, or both. Each pair of women shared certain characteristics, including mutation type, age, country, and history of ovarian cancer. Each pair included one woman who had been diagnosed with breast cancer and one who had not. Participants completed a questionnaire regarding their use of oral contraceptives based on their memory.

The researchers discovered that the use of oral contraceptives by women with the BRCA2 mutation was not associated with an increased risk of breast cancer compared to women who had not used the pill. For women with the BRCA1 mutation, use of the pill was associated with a modest increase in risk. However, women with the BRCA1 mutation and certain other characteristics had a significant increase in risk. For example, BRCA1 carriers who used oral contraceptives for five or more years had a 33% increase in risk of breast cancer compared to BRCA1 carriers who did not use oral contraceptives. In addition, women with the BRCA1 mutation who used the pill before 1975, when estrogen levels in the pill were higher, had a 42% increase in risk. Use of oral contraceptives before the age of 30 was associated with a 29% increase in risk for these women.

These findings apply only to women with the BRCA1 gene mutation, which can be detected through genetic testing. In light of this study, women who know they have this genetic mutation should discuss the pros and cons of birth control pills with their doctors. One benefit of taking the pill may be a decrease in the risk of ovarian cancer. A study published in the New England Journal of Medicine in 1998 showed women with either the BRCA1 mutation, the BRCA2 mutation, or both who took oral contraceptives for 5 years had a 60% decrease in risk of developing ovarian cancer compared to women who did not take the pill.

A woman’s age and how long she plans to use the pill should also be considered; use after the age of 30 and for fewer than five years was not associated with a significant increase in risk of breast cancer.

January 2003 Update

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Birth Control Pills and Breast Cancer

Good news for women who take the Pill — a new study, published in the June 27, 2002, issue of the New England Journal of Medicine, shows that current or former use of oral contraceptives does not increase the risk of breast cancer later in life.

Previous research indicated women who use or had used oral contraceptives in the past ten years were at an increased risk for breast cancer compared to women who had never used the Pill or had used it less recently. The new study was necessary now because the first generation of women to use the Pill at a younger age is reaching the period in their lives when the risk for breast cancer is greatest.

The study, conducted in Atlanta, Detroit, Los Angeles, Philadelphia, and Seattle, involved 4,575 women with breast cancer and 4,682 without. Study participants were between the ages of 35 and 64. Seventy-seven percent of the women with breast cancer and 79% of the women with no personal history of breast cancer had used oral contraceptives in their lives. The results were analyzed according to race, age, family history of breast cancer, and type of oral contraceptive used.

According to the results, women who took the Pill were as likely to have breast cancer as those who had never taken it. The results also showed the risk for breast cancer did not increase with longer periods of use or with higher doses of estrogen. Age, race, weight, and family history did not affect the risk of breast cancer in women using the Pill compared to women who did not.

Researchers interviewed only Caucasian and African American women. They also evaluated the risk of breast cancer in relation to a family history in first-degree relatives only (not including grandmothers, aunts, and cousins). Regardless, the results of this study should allay the fear that breast cancer may be related to use of the Pill.

August 2002 Update

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Long or Irregular Menstrual Period and Diabetes Risk

Women with long or highly irregular menstrual periods face twice the risk of developing adult-onset diabetes compared with women with regular periods, a new study suggests.

More than 100,000 women with no prior history of diabetes recorded their menstrual cycles and were tracked for eight years as part of the Nurse's Health Study.

One in every 95 subjects with cycles 40 days or longer developed diabetes, while only 1 in every 297 women with cycles of 26 to 31 days did. Women with cycles too irregular to measure also showed a significant increase in the occurrence of diabetes. The risk was modestly greater for women with a cycle length less than 21 days, though there were few women in this category and the connection was only found when there was a family history of the disease.

The link between a long menstrual cycle and diabetes was even stronger in obese women. Oral contraception use had no effect on risk. This was particularly interesting, because oral contraceptives may adversely affect insulin sensitivity and glucose tolerance, therefore increasing the woman's risk for diabetes.

In light of these findings, researchers suggest women with irregular or long menstrual cycles make an extra effort to control other risk factors for diabetes, such as excessive weight and lack of exercise.
January 2002 Update

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