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Radiation a major risk factor for breast cancer?

By David Liu, PHD

Sunday July 29, 2012 (foodconsumer.org) -- Last December a committee of the Institute of healths released a study report sponsored by Susan G. Komen for the Cure indicating that medical radiation and hormone-based therapy are two major risk factors for breast cancer for women in the United States.

The IOM press release says that women can reduce their risk for breast cancer by avoiding unnecessary medical radiation, forgoing use of estrogen-progestin menopausal hormone replacement therapy, limiting alcohol drinking, maintaining a healthy body weight, engaging physical exercise regularly and avoiding tobacco use.

In response to the report, Rebecca Voelker wrote an article in JAMA last January to add some details about how dangerous ionizing radiation used for medical diagnostics and disease treatment is.  She cited committee member Robert Hiatt, MD, PhD, of the University of California in San Francisco as saying "the amount of ionizing radiation from 3 abdominal CT scans is equivalent to levels that Japanese women were exposed to in the World War II atomic bomb explosions in Hiroshima and Nagasaki."
 
The IOM also says that evidence indicates it is possible although not as certain that breast cancer may be increased by exposure to benzene, 1,3-butadiene, and ethylene oxide which are chemicals found in some workplace settings and in car exhausts and tobacco smoke.

Ionizing radiation is recognized as a carcinogen by the National Toxicology Program.  Dr.  John Gofman, PHD and MD, a nuclear physician who passed away years ago said 75 percent of breast cancer cases have something to do with medical radiation and the damage by ionizing radiation is irreversible.  He said there is no safe dose and any amount of radiation causes damage and increases cancer risk.

The majority of doctors do not want to discuss with their cancer patients about the cancer risk posed by medical radiation fearing that patients may make a wrong decision and opt not to use radiation therapy.  The patients should have a right to know the risk they have to face and they are able to make an informed decision once they learn of all the benefits and risks associated with a particular treatment or diagnosis, some experts suggested.  Many cancer patients including breast cancer patients who receive radiation treatment end up developing other cancers such as leukemia and skin cancer.

Radiation can not only increase cancer risk but also risk for ischemic heart disease, according to Dr. Gofman. Many consumers are unaware of this risk and doctors may never bother to tell their patients about it.

In a study published in Oct 2011 in the journal Antioxidants & Redox Signaling, John E. Baker of Medical College of Wisconsin in Milwaukee, Wisconsin and colleagues reported that animals exposed to doses of 15 Gy or higher of radiation were at higher risk for cardiovascular disease.  Cancer patients commonly receive more than 15 Gy of radiation for treatment.  Such a dose is so high that radiologists have to administer it in weeks to minimize side effects so that the patients may tolerate the treatment.  Radiation on the chest as breast cancer treatment is particularly harmful to the heart.

It is not just radiation used to treat cancer can increase risk of cancer.  Studies have shown that radiation used in mammography intended for breast cancer screening may increase breast cancer risk.

Dr. Samuel S. Epstein, professor emeritus of Environmental and Occupational Medicine at the University of Illinois School of Public Health says on his website preventcancer.com postmenopausal women who undergo annual mammogram breast cancer screening for a ten-year period would receive exposure to about 10 rads of radiation for each breast.

He says each rad results in one cancer case in every 100 premenstrual women. A woman with exposure to 10 rads or receiving 10 screenings in 10 years would have a 10 percent risk of developing breast cancer, or 10 percent of women would develop the disease.

The risk of breast cancer from mammography is even greater in women with certain genetic variants.  Among women who carry A-T gene, the risk is four times higher. The radiation-induced breast cancer accounts for 20 percent of all breast cancers annually in the United States, Epstein says.

In the United States, more than 220,000 women are expected to be diagnosed with breast cancer each year and the disease kills more than 37,000 women each year in the U.S., according to the National Cancer Institute.