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Letter by Woodard et al Regarding Article, "Exposure to Low-Dose Ionizing Radiation From Cardiac Procedures and Malignancy Risk in Adults With Congenital Heart Disease".

September 25, 2018 1371 Pamela K. Woodard, MD Kathryn J. Lindley, MD Henry D. Royal, MD To the Editor: We read with interest the article by Cohen et al,1 and we agree that as low as reasonably achievable imaging in all patients, including those with congenital heart disease, is critical to good patient care. However, some flaws with the presented analysis should be considered. First, although the incidence of congenital heart disease surgery in the patients with cancer was less than in the patients without cancer, we do not know what percentage of the surgeries in each arm were Fontan repairs, which over time are associated with a significant increase in cirrhosis and development of hepatocellular carcinomas at a rate of 1.5% to 5.0% per year after Fontan.2 The authors also do not consider the incidence of transplant procedures in each arm. Patients receiving a transplant have a disproportionately high number of cancers, and differences in the number of patients receiving a transplant in the arms of the study could skew the results.3 The analysis should be corrected for increased incidence of hepatocellular carcinomas in patients undergoing a Fontan procedure and cancers in patients who have had transplant procedures. Moreover, this study does not meet any of the basic requirements for a valid radiation causation study. Basic requirements for a radiation causation study include organ dose assessment (the authors used effective dose), cancer incidence in exposed organs (authors assessed total cancer in each patient), and demonstration of a dose-response curve using organ doses. Thus, it is possible that this article overestimates the risk of cancer caused by imaging in this patient population, which clearly benefits from imaging in terms of surgical planning and follow-up. Moreover, the risk from suboptimal imaging, which may be caused by aggressive radiation-dose management decreasing the quality of the presurgical imaging road map, may indeed be greater than the risk of increased incidence of cancer in these patients. Indeed, thoughtful imaging in this patient population is needed, and the increased use of echocardiography and MRI, which do not expose the patient to ionizing radiation, should be considered. MRI maintains its own risks in repeated gadolinium-based contrast administration4 and in the sedation of young patients. Overall, keeping in mind that as low as reasonably achievable radiation exposure is critical, patients should receive the quality imaging they need to manage their patient care effectively.