Medical Imaging and Risk for Blood Cancers in Children and Adolescents

Radiation exposure from imaging studies, primarily computed tomography (CT), is a recognized risk factor for hematologic malignancy. To examine the relation between cumulative radiation exposure and risk for subsequent hematologic cancer, researchers retrospectively examined data on 3.7 million children and adolescents (a total of 35 million person-years) through age 21.

The researchers calculated radiation exposures from radiographs, fluoroscopy, angiography, nuclear medicine, and CT. Only cancer diagnoses that lagged exposure by at least 6 months were included, to avoid concerns that undiagnosed cancers had prompted the imaging. For reference, bone marrow doses of radiation for common studies vary by age of child, but the averages are 0.02 mGy for chest x-rays, 3.8 mGy for abdominal CTs, and 13.7 mGy for head CTs.

Nearly 3000 hematologic cancers were diagnosed. More than 7% of all children and 9% of those with hematologic cancers had received at least 1 mGy of cumulative radiation dose. Risks for hematologic malignancy increased with greater cumulative radiation doses: Compared with no exposure, patients' risk for hematologic malignancy was 1.4-fold higher with exposure of 1 to 5 mGy, 1.8-fold higher with exposure of 15 to 20 mGy, and 3.6-fold higher with exposure of 50 to 100 mGy. Translated to population-wide risks, exposures of ≥30 mGy were associated with 26 excess cancers by age 21 per 10,000 children.