Breast cancer primary prevention

, Jack Khouri

Phytoestrogens and soy
Phytoestrogens such as found in soybeans have been extensively studied in animal and human in-vitro and epidemiological studies. The literature support the following conclusions: It seems reasonable to conclude that soybean-based phytoestrogens are not a major contributor to the incidence of breast cancer.
 * 1) Plant estrogen intake, such as from soy products, in early adolescence may protect against breast cancer later in life.
 * 2) Plant estrogen intake later in life is not likely to influence breast cancer incidence either positively or negatively.

Folic acid (folate)
Studies have found that "folate intake counteracts breast cancer risk associated with alcohol consumption" and "women who drink alcohol and have a high folate intake are not at increased risk of cancer." A prospective study of over 17,000 women found that  those who consume 40 grams of alcohol (about 3-4 drinks) per day have a higher risk of breast cancer. However, in women who take 200 micrograms of folate (folic acid or Vitamin B9) every day, the risk of breast cancer drops below that of alcohol abstainers.

Folate is involved in the synthesis, repair, and functioning of DNA, the body’s genetic map, and a deficiency of folate may result in damage to DNA that may lead to cancer. In addition to breast cancer, studies have also associated diets low in folate with increased risk of pancreatic, and colon cancer.

Foods rich in folate include citrus fruits, citrus juices, dark green leafy vegetables (such as spinach), dried beans, and peas. Vitamin B9 can also be taken in a multivitamin pill.

Oophorectomy and mastectomy
Prophylactic oophorectomy (removal of ovaries), in high-risk individuals, when child-bearing is complete, reduces the risk of developing breast cancer by 60%, as well as reducing the risk of developing ovarian cancer by 96%.

Bilateral prophylactic mastectomies have been shown to prevent breast cancer in high-risk individuals, such as patients with BRCA1 or BRCA2 gene mutations.

Medications
Hormonal therapy has been used for chemoprevention in individuals at high risk for breast cancer. In 2002, a clinical practice guideline by the US Preventive Services Task Force (USPSTF) recommended that "clinicians discuss chemoprevention with women at high risk for breast cancer and at low risk for adverse effects of chemoprevention" with a grade B recommendation.

Selective estrogen receptor modulators (SERMs)
The guidelines were based on studies of SERMs from the MORE, BCPT P-1, and Italian trials. In the MORE trial, the relative risk reduction for raloxifene was 76%. The P-1 preventative study demonstrated that tamoxifen can prevent breast cancer in high-risk individuals. The relative risk reduction was up to 50% of new breast cancers, though the cancers prevented were more likely estrogen-receptor positive (this is analogous to the effect of finasteride on the prevention of prostate cancer, in which only low-grade prostate cancers were prevented). The Italian trial showed benefit from tamoxifen.

Additional randomized controlled trials have been published since the guidelines. The IBIS trial found benefit from tamoxifen. In 2006, the NSABP STAR trial demonstrated that raloxifene had equal efficacy in preventing breast cancer compared with tamoxifen, but that there were fewer side effects with raloxifene. The RUTH Trial concluded that "benefits of raloxifene in reducing the risks of invasive breast cancer and vertebral fracture should be weighed against the increased risks of venous thromboembolism and fatal stroke". On September 14, 2007, Steven Galson, director, US Food and Drug Administration's Center for Drug Evaluation and Research announced approval of the sale of raloxifene to prevent invasive breast cancer in postmenopausal women.