European questionnaire-based study leaves the question unanswered.

Because ionizing radiation can damage DNA, diagnostic x-ray exposure in individuals with defects in DNA repair mechanisms (such as those associated with BRCA1 and BRCA2 mutations) could lead to excess risk for cancer. Investigators surveyed women with documented BRCA1/2 mutations in the Netherlands, France, and the U.K. to evaluate any association between radiation exposure and later development of breast cancer. Questionnaires were administered to BRCA1/2 carriers from 2006 to 2009 to elicit their recollections of the type and number of diagnostic procedures they had received in their lifetimes. Estimates of radiation doses to the breast during each type of diagnostic procedure (mammography, fluoroscopy, and computed tomography and conventional radiography of the chest or shoulder) were used to determine total cumulative dose. Cases that were diagnosed >5 years before completion of the study questionnaire were excluded to prevent survival bias.

Of the 1993 participants, 43% (mean age, 49.7) had received diagnoses of breast cancer. Self-reported exposure to any form of diagnostic radiation before age 30 was associated with significantly higher risk for breast cancer (hazard ratio, 1.90; 95% confidence interval, 1.20–3.00), and risk rose with increasing cumulative dose. A history of mammography before age 30 was associated with nonsignificantly increased risk for breast cancer (HR, 1.43; 95% CI, 0.85–2.40). No evidence of excess risk was found for diagnostic radiation exposure between ages 30 and 39.

Comment: As with other epidemiologic studies of diagnostic radiation and risk for breast cancer in BRCA1/2 mutation carriers, the results of this study are inconclusive. The retrospective questionnaire design is subject to recall bias, especially given that women were asked to recollect events occurring up to 30 years earlier. Moreover, no attempt was made to document the date and type of radiologic tests that were reported. Furthermore, estimates of cumulative radiation dose were hypothetical and subject to wide variation based on factors in individuals as well as facilities. Until further data are obtained, the National Comprehensive Cancer Network recommendation of screening with magnetic resonance imaging and mammography in BRCA mutation carriers beginning at age 25 should be followed.

Source: Journal Watch Oncology and Hematology