Simple Lifestyle Changes Can Protect Against Breast Cancer

 Behind the Cancer Headlines®

December 16, 2005

Preventing cancer, rather than treating it after it appears, may ultimately be the key to breast cancer control. Leslie Bernstein, PhD, from the University of Southern California Norris Comprehensive Cancer Center, addressed this issue at the 28^th Annual San Antonio Breast Cancer Symposium. According to Bernstein, risk factors that may lead to cancer can frequently be modified, some through the use of drugs or surgery, but some through simple lifestyle changes. 

Risk factors for breast cancer can generally be divided into those that cannot be changed and those that can. Risk factors that cannot be changed include age, gender, race/ethnicity, early noncancerous changes in the breast, family history of breast cancer, age at first menstrual period, and age at menopause. Those that can be changed include pregnancy history (number of births, no births), removal of the ovaries prior to menopause, lactation, density of the breasts as shown during mammography, past radiation treatment, physical activity, postmenopausal obesity/adult weight gain, hormone therapy, and alcohol intake. 

How do these factors affect the risk of breast cancer? The answer is complex. For example, pregnancy/lactation may protect against breast cancer by reducing subsequent circulating estrogen levels, or because of changes in the breast that result from high levels of estradiol and progesterone, or perhaps in response to varying levels of another hormone called human chorionic gonadotropin. Can we develop a prevention strategy using this knowledge, based on mimicking the hormonal environment that occurs in a pregnant woman? 

We do know that the risk of breast cancer can be significantly reduced by taking tamoxifen, a drug that is chemically similar to estrogen but blocks estrogen action. Unfortunately, many women at risk for breast cancer are reluctant to take tamoxifen, because of the potential for side effects, including severe hot flashes and possible uterine cancer. For some women at very high risk (for example, those with specific gene mutations associated with breast cancer), the prophylactic removal of both breasts may be an option, but again, most women are reluctant to pursue this. 

Many women would prefer to consider lifestyle changes. Obesity in postmenopausal women (usually defined as a body mass index >27) is associated with increased risk, with about 7.6% of breast cancers in the United States attributable to obesity. Thus, simple weight loss is a feasible strategy. Exercise in women of reproductive age, especially in younger women and teenagers, can have a significant effect on the occurrence of breast cancer, possibly due to disturbances in the menstrual cycle that result in reduced hormone levels. Lifetime physical activity is associated with lower risk of invasive breast cancer among women in Europe and Asia and among Asian-American and Hispanic-American women. In contrast to the risk associated with obesity, in this case risk reduction is greater among women without a first degree family history of breast cancer. 

There are also dietary factors that may affect breast cancer risk. For example, biologically active compounds from green tea have been shown to suppress the growth of human breast cancer cells injected into mice, and consumption of green tea is associated with reduced breast cancer risk in Asian-American women. 

Bernstein pointed out that, as opposed to pharmacological and surgical strategies, these lifestyle changes have the advantage of being cost-effective and likely to meet with greater patient acceptance. Further research needs to address questions about the importance of age of exposure, duration of exposure, and exposure intensity, as well as the size of the benefit that can be obtained from lifestyle changes. 

SOURCE: 

San Antonio Breast Cancer Symposium, December 12, 2005, San Antonio, TX