Early life ionizing radiation exposure and cancer risks: systematic review and meta-analysis

Background Ionizing radiation use for medical diagnostic purposes has substantially increased over the last three decades. Moderate to high doses of radiation are well established causes of cancer, especially for exposure at young ages. However, cancer risk from low-dose medical imaging is debated. Objective To review the literature on cancer risks associated with prenatal and postnatal medical diagnostic ionizing radiation exposure among children and to assess this risk through a meta-analysis. Materials and methods A literature search of five electronic databases supplemented by a hand search was performed to retrieve relevant epidemiological studies published from 2000 to 2019, including patients younger than 22 years of age exposed to medical imaging ionizing radiation. Pooled odds ratio (ORpooled) and pooled excess relative risk (ERRpooled) representing the excess of risk per unit of organ dose were estimated with a random effect model. Results Twenty-four studies were included. For prenatal exposure (radiographs or CT), no significant increased risk was reported for all cancers, leukemia and brain tumors. For postnatal exposure, increased risk was observed only for CT, mostly for leukemia (ERRpooled=26.9 Gy(-1); 95% confidence interval [CI]: 2.7-57.1) and brain tumors (ERRpooled=9.1 Gy(-1); 95% CI: 5.2-13.1). Conclusion CT exposure in childhood appears to be associated with increased risk of cancer while no significant association was observed with diagnostic radiographs.