Pediatric Cancer

PV QA 3 - Poster Viewing Q&A 3

TU_24_3103 - Low Dose Rate in Preventing Pulmonary Toxicities for Pediatric Total Body Irradiation Patients

Tuesday, October 23
1:00 PM - 2:30 PM
Location: Innovation Hub, Exhibit Hall 3

Low Dose Rate in Preventing Pulmonary Toxicities for Pediatric Total Body Irradiation Patients
N. B. Boyce1, R. A. Dahl1, S. K. Ahmed1, and N. N. Laack II2; 1Mayo Clinic, Rochester, MN, 2Department of Radiation Oncology, Mayo Clinic, Rochester, MN

Purpose/Objective(s): Pulmonary toxicity (PT) is common after total body irradiation (TBI) for bone marrow transplant. Prior studies suggest PT is as high as 70% and may be dose-rate and treatment technique dependent. Conflicting reports suggest toxicity may differ between AP/PA with partial transmission blocks versus lateral technique with arm shielding. This study aimed to characterize PT in a homogeneously treated population using lateral treatment technique and to evaluate the effect of dose-rate on incidence of PT.

Materials/Methods: The medical records of patients <21 years of age treated with TBI as a component of stem cell transplantation from 1993-2017 were retrospectively reviewed. All patients in this study received TBI using lateral technique. The incidences of PT, graft versus host disease (GVHD), and other toxicities were recorded for each patient. The category of PT was subdivided into infectious etiology and noninfectious etiology, which was classified by clinical symptoms, pulmonary function test results, and radiographic evidence. The association of PT with other variables was examined using chi-square tests. Overall survival (OS) was estimated by the Kaplan-Meier method.

Results: The cohort consisted of 61 patients. With a median follow up of 3.2 years (range: 0.5 months – 23.0 years), the three-year OS was 65% (95% CI, 54-79%). Indications for transplant included: leukemia, 45 patients; myelodysplastic syndrome, 6 patients; lymphoma, 4 patients; neuroblastoma, 2 patients; and sarcoma, 4 patients. Median TBI dose was 1320 cGy (range: 1000-1320 cGy), and median TBI dose rate was 7.70 cGy/min (range: 4.0-10.1 cGy/min). PT was documented in 20 patients (33%), with an infectious etiology documented in 8 patients (42%). The median time to PT diagnosis after completion of TBI was 0.63 months (range: 0.02-14.7 months). A higher rate of PT was observed in patients with GVHD (65% vs. 35%, p<0.01). TBI dose rate (

Conclusion: A relatively low incidence of PT was observed in this cohort of patients treated with low dose rate, bilateral TBI technique, and total dose of 1000-1320 cGy. Dose rates in the range of 4.0-10.1 cGy/min are associated with acceptable rates of PT.

Author Disclosure: N.B. Boyce: None. R.A. Dahl: None. N.N. Laack: Research Grant; Bristol Myers Squibb, National Institutes of Health. Vice Chair, Bone Committee; Children's Oncology Group.

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