Imaging in childhood cancer: a Society for Pediatric Radiology and Children's Oncology Group Joint Task Force report

Abstract

Contemporary medical imaging is a cornerstone of care for children with cancer. As 5-year survival rates for children with cancer exceed 80%, imaging technologies have evolved in parallel to include a wide array of modalities. Here, we overview the risks and benefits associated with commonly used imaging modalities and survey the current landscape of medical imaging for children with cancer. We find evidence-based imaging guidelines to assist in protocol development and to guide decision-making for optimal patient care are often lacking. The substantial variation in protocol-based recommendations for imaging both during and following therapy may hinder optimal clinical research and clinical care for children with cancer.

Fig. 1

Estimated attributable lifetime risk from a single small dose of radiation as a function of age at exposure [7]. Females have higher risk due to breast and thyroid cancers. Younger age at exposure imparts greater risk that is usually not expressed until late in life [5]. Grays (Gy) is the unit of measurement of the absorbed dose. (Reprinted with permission from the National Academies Press, Copyright 2006, National Academy of Sciences.)

Fig. 2

Effective dose estimates of frequently used imaging modalities in relation to common exposures for a 10-year-old child [4,9]. Effective dose summates the absorbed organ doses in the exposed field and multiplies it by a weighting factor determined by the differential radiosensitivity of the organ, and is expressed in Sieverts (Sv). One Sievert equals 100 rem (roentgen equivalent man), and is roughly equivalent in biological effectiveness to one Gy (gray) of gamma radiation. It is important to note that these are estimates only and actual effective dose is dependent of patient body habitus, equipment settings and equipment manufacturer; doses can vary significantly within and across institutions and may vary amongst machines. Unless appropriate adjustments are made in exposure settings, pediatric patients receive higher effective doses of radiation than adult patients because their smaller size leads to less attenuation of the primary X-ray beam; these adjustments are now made in most pediatric and academic hospitals [89]. *If best practices are followed (see www.imagegently.org), the effective dose estimates may be lower than those noted (e.g., mean dose for a chest CT could be as low as 1.6 mSv based on a correction factor of 0.013 mSv/mGy/cm [90] applied to values derived from Ref. [91]).

Fig. 3

Typical chest imaging involving ionizing radiation for select higher risk primary cancer diagnoses, based on Children’s Oncology Group research protocols (AEWS02P1, ARMS0431, AHOD0831, and AREN0533), available via clinicaltrials.gov (identifier NCT00061893, NCT00354744, NCT01026220, and NCT00379340, respectively; left panel). Cumulative effective dose of ionizing radiation from chest CT scans from staging through to 5 years from diagnosis, estimated based on 4.1 mSv per study in a 10-year-old (right panel). Note that effective dose per study is likely less at pediatric imaging centers. In addition, when multiple examinations are performed, the risk per mSv is reduced by at least 50%. EWS, Ewing sarcoma; RMS, rhabdomyosarcoma; HD, Hodgkin lymphoma.