by Rosanna Grobbink, B.Sc, ND (Cand)
As practitioners with a special interest in the prevention of disease, naturopathic oncologists often are asked by patients to discuss the topic of potential risks involved with various types of diagnostics. A common concern of a patient is the long term effect of radiation emitting imaging. This is especially a concern if the imaging must be repeated frequently.
There has been continuous debate about the most appropriate screening guidelines for breast cancer. The risks of various forms of screening (self and clinical breast exam, radiographic imaging and MRI) must be weighed against the benefits. Recently there has been ample media attention given to the topic of mammography increasing the risk of breast cancer in women with known genetic risk factors, specifically BRCA1/2 gene mutation carriers. The BRCA1/2 genes are responsible for repair of DNA double strand breaks and known mutations of these genes are associated with increased risk of breast cancer. A recent study published in the British Medical Journal examined patients that were carriers of the BRCA1/2 mutation and correlated their exposure to radiation with a subsequent increase in the risk of breast cancer.
The study, which was published in September 2012, was a retrospective cohort study of 1993 female carriers of BRAC1/2 mutations, from France, the UK and Netherlands. This study was proposed based on an established risk between ionizing radiation and breast cancer in the general population when exposure occurred during childhood and adolescence compared to exposure during adulthood. The researchers hypothesized an increased risk of radiosensitivity for individuals with BRCA1/2 gene mutations.
The female carriers were evaluated for their risk of breast cancer based on their self-reported exposure to diagnostic radiation from a questionnaire about lifetime exposure of radiation to the chest/shoulders. Participants were asked about imaging indications, ever/never exposure, age at first exposure, number of exposure before age 20, and at ages 20-29, 3 -39 and age at last exposure. This information was used to calculate the cumulative breast dose in Gy units based on breast dose for various radiographic techniques.
The information gathered in the study was subjected to a Cox proportional hazard model to calculate adjusted hazard ratios of breast cancer and 95% confidence interval with age (in years) as the time scale and cumulative radiation exposure from diagnostic procedures as a time dependent variable. The researchers adjusted to exclude procedures that could have been used as a result of the diagnosis of breast cancer, exclusion of radiation that most likely did not contribute to the development of breast cancer, survivorship bias, testing bias and family history.
The study reported carriers of the BRAC1/2 mutation who were exposed to any radiation before the age of 30 had an increased risk of breast cancer in a dose-response pattern (hazard ratio 1.90, 95% confidence interval 1.20 to 3.00). For cumulative doses estimates of greater than 0.0174 Gy there was almost a four-fold increase risk of breast cancer for those exposed before the age of 30. There was no associated risk of breast cancer for radiation exposure between the ages of 30 to 39. The study also reports analyses of different types of diagnostic procedures showed a pattern of increasing risk with increasing number of radiography before the age of 20 and age of 30 when compared to no exposure.
Based on these results, the authors of the study conclude there is evidence to support using non-ionizing radiation imaging techniques (such as MRI) as the main tool for surveillance in women under 30 with BRAC1/2 mutations. It is important to continue to evaluate new available literature and to increase the efficacy of screening programs while reducing the chances of increasing risk factors for these patients.