Genes and Breast Cancer:  
Perspective &  Prevention

 by Kumara Sidhartha, MD

Among Massachusetts women, breast cancer tops the list of cancers. It is more common than lung, colon & skin cancers, all combined. Breast cancer and its genetic risks are in the news following the poignant article published in the New York Times by actress Angelina Jolie describing her decision to undergo double mastectomy. To put genetic risk into perspective, it is important to understand the role of genes in cancer within the context of other significant risks for breast cancer.

Cancer prevention is a built-in feature in our cells. Cancer-inducing genes in our bodies are tightly balanced with protective, cancer-suppressing genes. Unfortunately, this balance tips toward cancer when inherited genetic errors cripple protective genes such as BRCA 1 or 2.

The majority of breast cancers though are unrelated to inherited BRCA gene defects. In fact, nine out of ten breast cancers are not related to inherited gene defects. 

Inheriting a defective gene is not an inevitable fatal blow to every person involved. Researchers Sining Chen and Giovanni Parmigiani conclude that nearly half the women carrying defective BRCA 1 or 2 genes do not develop breast cancer. Differences in lifestyle habits may explain why every person carrying the defective gene does not get breast cancer.

Healthy lifestyle protects against breast cancers - both non-genetic and genetic. Nearly half of all the non-genetic breast cancers can be prevented by avoiding these risks:

• Excess body weight,
• Alcohol consumption of more than one drink per week,
• Physical activity of less than five hours per week, and

A healthy lifestyle may even trump inherited gene defects. Dr.Dean Ornish, in a small study, showed that lifestyle changes including 100% plant-based diets can turn-on protective genes and turn-off harmful genes of prostate cancer. Among women, eating a diversity of food while including more vegetables, fruit, whole grains and legumes, and reducing excess dietary protein and cholesterol appears to protect some even with BRCA gene defects, according to an analysis of tens studies in 2007 by researchers A. Nkondjock and P. Ghadirian.

So who should consider getting tested for the presence of BRCA 1 & 2 gene defects? According to the National Cancer Institute, women of Ashkenazi Jewish descent need to consider genetic testing if:

• any first-degree female relative (mother, daughter, or sister) is diagnosed with breast or ovarian cancer or
• two second-degree relatives  (grandmother or aunt) on the same side of the family are diagnosed with breast or ovarian cancer.

For all other women, consider testing if you have:

• two first-degree relatives diagnosed with breast cancer, one of whom was diagnosed at age fifty or younger;
• three or more first-degree or second-degree relatives diagnosed with breast cancer regardless of their age at diagnosis;
• a combination of first- and second-degree relatives diagnosed with breast cancer and ovarian cancer (one cancer type per person)
• a  first-degree relative with cancer diagnosed in both breasts
• a combination of two or more first- or second-degree relatives diagnosed with ovarian cancer regardless of age at diagnosis;
• a first- or second-degree relative diagnosed with both breast and ovarian cancer regardless of age at diagnosis;
•  breast cancer diagnosed in a male relative.

The testing process involves counseling by a geneticist to discuss the pros and cons of having the test done. Based on results, further treatment needs to be tailored to the particular individual's risk for breast cancer.   

The good news is that 98%of women in the US will not fit these risk profiles and hence need not pursue genetic testing for BRCA 1 or 2. But this rare nature of the defects also means that BRCA studies have fewer participants, and the fewer participants a research study has, the weaker the strength of its evidence. Given such limitations in BRCA research, answers emerge slowly, bit-by-bit.

Until more robust data is available, you can take these five steps to move from fear to hopeful action, regardless of your genetic tendencies: 1. Increase your dietary fiber in the form of legumes and whole grains, 2. Eat a variety of antioxidant-rich, colorful vegetables in abundance, 3. Exercise regularly, 4. Avoid weekly consumption of alcohol, and 5. If you smoke, quit.

Kumara Sidhartha MD is a primary care physician accepting new patients at the Cotuit office of Emerald Physicians, Cape Cod, MA. He is currently studying Master of Public Health Nutrition at the online School of Public Health at University of Massachusetts, Amherst.