Women carrying a mutation in the BRCA1- or BRCA2- (breast cancer) genes who have undergone diagnostic radiation to the chest before the age of 30 are more likely to develop breast cancer than those who carry the gene mutation but have not been exposed, according to a study published Sept. 6 in British Medical Journal. The authors recommended that clinicians use non-ionizing imaging modalities for surveillance imaging of BRCA 1/2 mutation carriers.
Researchers have suggested that women with a mutated BRCA 1/2 gene could have increased radiosensitivity because of impaired DNA repair mechanisms. Thus, the benefit from mammographic screening in young BRCA 1/2 mutation carriers may not outweigh the risk.
Anouke Pijpe, Msc, postdoctoral research fellow from the Netherlands Cancer Institute in Amsterdam, and colleagues sought to estimate the risk of breast cancer associated with diagnostic radiation in carriers of BRCA 1/2 mutations and studied 1,993 female BRCA 1/2 mutation carriers in the Netherlands, France and the U.K. between 2006 and 2009. Follow-up ended with diagnosis of first breast cancer. All patients were aged 18 or older.
Women were questioned on radiation exposure via x-ray or CT of the chest/shoulders, mammogram, fluoroscopy and other diagnostic exams. Women also listed age at first exposure, number of exposures before age 20, at ages 20 to 29, 30 to 39 and age at last exposure. Researchers estimated cumulative breast dose in units of Gy.
Pijpe and colleagues conducted an analysis of the entire cohort and of a subcohort of cases within the last five years, which was designed to correct for potential survival bias.
Results showed that 43 percent of the 1,993 women were diagnosed with breast cancer. A total of 48 percent reported ever having an x-ray and 33 percent had a mammogram. The average age at first mammogram was 29.5 years.
A history of any exposure to diagnostic or screening radiation to the chest at ages 20 to 29 increased breast cancer risk by 43 percent and any exposure before the age of 20 increased breast cancer risk by 62 percent. No association with breast cancer was apparent for exposures at ages 30 to 39.
“We also observed a pattern of increasing risk with increasing dose; for a cumulative dose estimate of more than 0.0174 Gy we observed an almost fourfold increased risk of breast cancer. A similar increased risk was observed for exposure before age 20 even after a lower dose of more than 0.0066 Gy.”
Pipje and colleagues concluded, “In this large European study among BRCA 1/2 mutation carriers, 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 results of this study support the recommendation to use non-ionising radiation imaging techniques (such as MRI) as the main tool for surveillance among young BRCA 1/2 mutation carriers.”