Ionizing radiation imaging raises breast cancer risk in BRCA1/2 carriers

By Lynda Williams, Senior medwireNews Reporter

Exposure to ionizing radiation at an early age increases the risk for breast cancer among women with BRCA1/2 mutations, reveals research published in the BMJ.

Results taken from three studies conducted in France, the UK, and the Netherlands show that women with the mutations who were exposed to diagnostic radiation before the age of 30 years were a significant 1.9 times more likely to develop breast cancer than those who were not.

This increased risk roughly followed a dose-response relationship, with a hazard ratio (HR) of 1.63 for patients exposed to less than 0.0020 Gy by 30 years, rising to 3.84 for patients exposed to more than 0.0174 Gy or more.

A similar risk was found for exposure before the age of 20 years, with a HR of 3.16 for a dose of 0.0066 Gy or above, whereas there was no increased risk found for patients exposed between ages 30 and 39 years.

Noting that the doses associated with an increased risk were significantly lower than previously reported for individuals, even after adjusting for early mammogram screening due to family history, Flora van Leeuwen (Netherlands Cancer Institute, Amsterdam) and co-workers say: "The results of this study support the recommendation to use non-ionising radiation imaging techniques (such as [magnetic resonance imaging]) as the main tool for surveillance in young BRCA1/2 mutation carriers."

Overall, 48% of the 1993 women recruited in 2006 to 2009 for the GENEPSO, EMBRACE, and HEBON trials for women with a BRCA1/2 mutation were diagnosed with breast cancer.

Around half (48%) had undergone radiography and 33% had received a mammogram, with a median of 2.4 and 2.2 of procedures before the age of 40 years per women, respectively. Less than 5% had undergone computed tomography. The average estimated dose from ionizing radiation imaging was estimated to be 0.0140 Gy.

Further analysis confirmed the increased risk for breast cancer with any ionizing radiation imaging exposure before age 30 years in BRCA1 carriers (HR=2.83), and the dose-response effect, with a HR of 5.00 for a dose of 0.0174 Gy and above.

No such significant association was found between exposure and risk among BRCA2 carriers, although the researchers note that this may be due to the small number of patients.

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