By David Liu, PHD

Wednesday Oct 31, 2012 (foodconsumer.org) -- There should be no denying of the fact that ionizing radiation even in a low dose can increase risk of breast cancer and the risk is particularly significant in those whose genetics makes them more vulnerable than others.

A new study published in Sept 2012 in British Medical Journal confirmed an early finding that exposure to low doses of ionizing radiation such as that used in mammogram screening and other radiation-based diagnostic tools can increase risk of breast cancer in carriers of BRCA1/2 mutations.

A. Pijpe from Netherlands Cancer Institute, Department of Epidemiology and Biostatistics in Amsterdam, Netherlands and colleagues conducted the restrospective cohort study to examine the risk of breast cancer associated with diagnostic radiation in women with BRCA1/2 mutations.

They found women with BRCA1/2 mutations who were exposed to diagnostic radiation before the age of 30 years were almost twice as likely as those who were not to develop breast cancer.

The study of 1993 female carriers of BRCA1/2 mutations, enrolled from 2006 through 2009 in three nationwide studies (GENEPSO, EMBRACE, HEBON) in France, United Kingdom, and the Netherlands also found the risk of breast cancer associated with the diagnostic radiation was dose-responsive.

Women whose exposure doses were in the highest quartile were almost four times as likely as those who were not exposed to diagnostic radiation to develop breast cancer.  Even those whose exposure doses were in the lowest quartile had 63 percent increased risk of the disease.

Further, the study showed a pattern: a higher number of radiographs was associated with a higher risk of breast cancer in those who were exposed to radiation before age 20 and before age 30, compared with those without exposure to diagnostic procedures.  A history of mammography screening before age 30 was also correlated with an 43 percent increased risk of breast cancer. 

The researchers were able to ascertain with sensitivity analysis that this association was not caused by confounding by indication of family history.

The researchers concluded "In this large European study among carriers of BRCA1/2 mutations, exposure to diagnostic radiation before age 30 was associated with an increased risk of breast cancer at dose levels considerably lower than those at which increases have been found in other cohorts exposed to radiation."

The study abstract did not say how radiation exposure affect the risk of breast cancer after age 30.  Prior evidence has suggested that mammogram screening also has a cancer causing effect on the breast cancer risk, particularly in women with BRCA 1/2 mutations.  It's just that women who are younger are at a higher risk if they are exposed to the same dose of radiation.

Ionizing radiation has been recognized as a human carcinogen by the National Toxicology Program.  Ironically, such a cancer-causing agent is used to diagnose and treat many types of cancers including breast cancer. In reality, radiatherapy kills cancer cells and in the meantime cause carcinogenesis in healthy cells that can lead to future cancers.

John Gofman, Ph. D. M.D. late nuclear physician, said medical radiation is involved in 75 percent of breast cancer cases.

Exposure to radiation on the chest also increases risk of ischemic heart disease, which is less publicized than the cancer-causing effect.

Breast cancer is expected to be diagnosed in more than 230,000 women in 2012 in the United States and the disease is expected to kill about 37,000 in the same year and same country.

An authoritative organization says that two most important risk factors for breast cancer are medical radiation and hormone therapy.  Other risk factors such as exposure to pesticides are minor players.

Women who definitely want to receive mammograph screening may consider taking high doses of vitamin C in a few days before and after the procedure.  Studies show that vitamin C can reduce the damage induced by radiation.