Impact of using volumetric dosimetry to screen childhood cancer survivors for radiation-related late effects.

Abstract

12066 Background: Late effects screening guidelines for survivors of childhood cancer treated with radiation therapy currently use irradiated regions (IR) rather than volumetric dosimetry (VD), which more precisely identifies organs-at-risk (OAR). We recently showed that VD reduced mean number of recommended screening diagnostic imaging studies and procedures by 37.0% per patient (p<0.001).1 Here we have incorporated chemotherapy and refined volumetric dosimetry dose thresholds. Methods: This was a cross-sectional cohort study of patients (n=132) treated for cancer using computerized tomography-planned irradiation at Children’s Hospital Los Angeles from 2000-2016. For each patient, both VD and IR methods were used to determine radiation exposure to the cochlea, heart, lung, breast, and colon. Dose thresholds for VD were based on those supplied in the Children’s Oncology Group (COG) Long-Term Follow-Up Guidelines. Relevant chemotherapy exposures were recorded. Under each method, COG Long-Term Follow-Up Guidelines were applied to determine potential chemotherapy- and radiation-related late effects and their correlative screening practices (complete audiologic evaluation, pure tone audiometry, mammogram, breast MRI, echocardiogram, pulmonary functions test, and/or colonoscopy). Identified OAR were compared using Exact McNemar’s test. Total numbers of screening practices were computed using VD and IR and compared. Results: Median age at end of treatment was 10.6 years (range 1.4-20.4). The most frequent cancer type was brain tumor (45%), followed by bone and soft tissue tumor (39%) and leukemia/lymphoma (16%). Head/brain was the most commonly irradiated region (61%), followed by abdomen (22%). Anthracyclines were received by 25% of patients at < 250 mg/m2 and by 16% at ≥ 250 mg/m2. With use of VD, fewer patients were flagged for screening for each organ of interest: cochlea (-21.3%, p<0.001), heart (-22.5%, p<0.001), lung (-13.8%, p=0.219), breast (-25%, p=0.625), colon (-51.9%, p<0.001). Over the lifetime of this cohort, use of VD resulted in recommendations for 1,333 fewer pure tone audiometric tests (-21.5%), 9 fewer complete audiologic evaluations (-16.1%), 4 fewer pulmonary function tests (-13.8%), 112 fewer mammograms (-25.0%) and breast MRIs (-25.0%), 349 fewer echocardiograms (-16.1%), and 275 fewer colonoscopies (-51.9%). Conclusions: Use of VD rather than IR significantly reduces guideline-based screening for radiation-related late effects in long-term childhood cancer survivors. This work forms the basis for a comparative cost-effectiveness analysis of these two approaches. (1) Cohen-Cutler et\xa0al, Cancer Medicine, 2020.