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Study Explores Why Pregnancy at An Early Age Reduces Breast Cancer Risk (dateline October 31, 2001)

Researchers have known for some time that having children at a young age decreases a woman’s risk of breast cancer. Now, a new study provides data that may help explain why this is the case. The research involved studying the levels of a tumor suppressor protein called p53 in rats. According to the researchers, early pregnancy increases the amount of p53 in the rat’s bodies, which appears to provide protection against breast cancer. Though the study results are preliminary and need to be evaluated in humans, the researchers believe that the study suggests that a drug therapy could be developed based on p53 levels that could make young women resistant to breast cancer.

While there is no sure-fire method of preventing breast cancer, it is known that having children before age 30 can decrease a woman’s risk of developing the disease. This is because pregnancy involves an interruption of menstrual cycles, which is thought to provide protection against both breast cancer and ovarian cancer. However, pregnancy after age 30 does not appear to provide protection against breast cancer, and in fact, it is thought to increase the risk of breast cancer.

Dr. Bert W. O’Malley and his colleagues from the Baylor College of Medicine in Houston, Texas set out to examine why pregnancy at an early age decreases breast cancer risk. Dr. O’Malley and his team gave estrogen and progesterone to young female rats in the study to simulate increased hormone levels associated with pregnancy. The researchers discovered that early pregnancy resulted in increased levels of p53 in the rats compared with untreated rats of the same age group. However, administering estrogen and progesterone to older rats did not produce the same results, suggesting that only early pregnancy enables the body to protect against breast cancer.

p53 is a tumor suppressor protein that decreases breast cancer risk. According to Dr. O’Malley and his colleagues, short exposure to estrogen and progesterone associated with pregnancy early in life leads to continuously higher levels of p53. Previous studies have shown that women who carry abnormal forms of the p53 protein have a higher risk of breast cancer because their bodies are less able to protect against the disease.

Though the research is compelling, it must be confirmed in additional studies. Dr. O’Malley and his team are not certain whether the effect of early pregnancy on p53 levels is the same in humans as it is in rats. However, if future human studies do yield similar results, the researchers suggest that a drug could be developed based on the p53 effect to reduce breast cancer risk in young women. Currently, Dr. O’Malley and his colleagues are investigating the mechanism that contributes to the elevation of p53 in the body.

In addition to pregnancy at an early age, several other factors have been identified as having an effect on a woman’s risk of breast cancer. For example, the following factors have been associated with a higher than average risk of breast cancer:

To help detect breast cancer in early stages when it can often be easily treated, all women 40 years of age and older should have yearly mammograms and clinical breast exams and practice monthly breast self-exams. Women younger than age 40 should also have regular clinical breast exams and practice monthly breast self-exams.

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