How much is too much? Systematic review of cumulative doses from radiological imaging and the risk of cancer in children and young adults

BACKGROUND: While medical imaging plays a key role in diagnostic and treatment guidance, evidence shows that the number of investigations using ionizing radiation has greatly increased over the last decades, which could be a concern among paediatric patients. Repeated imaging, as required for certain congenital conditions is of particular interest in regard to cumulative dose and the associated risk of cancer. In this context, the aim of the current work is to systematically collate and evaluate the findings reported in the literature over the last 10 years, based on the imaged anatomical area, in order to identify trends, consensus and/or discrepancies in reported risks.

METHODS AND FINDINGS: Two databases (MEDLINE, and Scopus) were systematically searched for literature published between 2010 until July 2020. Randomized clinical trials (RCTs), controlled clinical trials (CCTs), prospective and retrospective cohort studies, and case series (with ≥10 cases) were sought. Forty-five studies met eligibility criteria for inclusion in the review, with all studies achieving good-to-high-quality ratings based on the Critical Appraisal Skills Programme (CASP) assessment. The eligible articles were divided into different groups, according to the irradiated anatomy, considering that anatomy-specific assessment has important implications for future study designs, by accounting for the physiological and radiobiological particularities of a specific organ or tissue.

CONCLUSIONS: Although majority of the reports present certain limitations concerning the study design or data analysis, there is a general agreement regarding paediatric exposure that require a number of key measures to reduce long-term effects, such as: dose reduction by employing non-ionizing imaging modalities, whenever possible, or plain radiographs; use of CT imaging selectively rather than routinely; use of dedicated scan protocols for each imaging modality and device; recording of specific exposure parameters for each patient during the procedure for more accurate dose calculations; creation of dose registries for paediatric exposure; cumulative dose monitoring for long-term risk analysis; and comparative dose-risk analysis among various imaging modalities for different conditions in order to evaluate the most optimal choice for each situation.