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Physical Activity cuts breast cancer risk even in BRCA mutation carriers

Below is a report intended to remind our readers that physical activity can help reduce the risk of breast cancer even in BRCA1 and BRCA2 mutation carriers.
BRCA1 and BRCA2 are human genes that belong to a class of genes known as tumor suppressors. Mutations of these genes disable the genes' anticancer functions, thus raising the risk of developing breast cancer and other female reproductive cancers like ovarian cancer.
A study published in the journal Breast Cancer Research and Treatment suggests that simply engaging in physical exercise and sports activity may significantly reduce the risk of breast cancer in women who carry BRCA1/2 mutations.
For the study, Anouk Pijpe at the Netherlands Cancer Institute and colleagues studied the association between self-reported lifetime sports activity and breast cancer risk in a study population including 725 BRCA1/2 mutation carriers, of whom 218 had been diagnosed with breast cancer, within 10 years prior to the survey about their lifestyle.
Those who participated in sports activities were at a 16 percent reduced risk of breast cancer, but the reduction was considered statistically insignificant.
Among women who had ever engaged in sports activity, those who had 11 to 22.7 mean MET hours per week over a lifetime reduced their risk of breast cancer by 41 percent.
Engaging in sports activity both before and after age 30 was inversely associated with breast cancer risk in BRCA1/2 mutation carriers.
It is unknown why physical activity reduces the risk. Physical activity is known to help metabolize the female sex hormone estrogen and prevent it from accumulating to harmful levels -- estrogen is known to promote the development of breast cancer.
Another explanation, which is rarely mentioned in media reports and research reports, is that physical activity promotes blood circulation by pumping oxygen quickly to the location that is needed.  Cancer cells do not grow well when oxygen is present, a fact that is well known by cancer researchers. 
Women with BRCA1 or BRCA2 or mutations of both genes are at much higher risk of breast cancer than noncarriers.  
Allison W. Kurian and colleagues at Stanford University School of Medicine and colleagues in 2009 published a study in the Journal of Clinical Oncology saying the survival probability by age 70 is 53 percent for BRCA1 mutation carriers and 71 percent for BRCA2 mutation carriers.
One needs to know what these researchers found to appreciate the protective effect of physical activity against breast cancer in BRCA mutation carriers.
According to the researchers, prophylactic oophorectomy, or surgically removing ovaries at age 40 years, can boost survival rate by 15 percent for those with BRCA1 mutations and prophylactic mastectomy or surgically removing the breast, which is considered most effective for BRCA2 mutation carriers, boosted a survival rate by merely 7 percent.

Physical activity also cuts risk of death from breast cancer in non BRCA mutation carriers.

A recent study published in the April 22, 2010 issue of Medical Oncology shows that post-diagnosis physical activity reduced breast mortality by 34 percent and physical activity in general reduced mortality by 41 percent.
The study led by Ibrahim E. M. and Al-Homaidh A. from International Medical Center in Kingdom of Saudi Arabia involved 12,108 patients with breast cancer.
Breast cancer will be diagnosed in more than 175,000 women and kills about 50,000 each year in the United States, according to the National Cancer Institute. One in eight women in this country is expected to develop the disease sooner or later in their lifetime.
More studies will be reported on foodconsumer.org in the National Breast Cancer Awareness Month to help readers better understand the disease and how to prevent it.  In addition to wearing pink, many other things can be done to reduce the risk.

David Liu and editing by Rachel Stockton