Delivery of re-irradiation and complex palliative radiotherapy using proton therapy in pediatric cancer patients.

ABSTRACT

BACKGROUND: The intent of this study is to characterize indications for pediatric palliative-intent proton radiation therapy (PIPRT). PROCEDURE We retrospectively reviewed patients 21 years and younger who received PIPRT. We defined PIPRT as radiotherapy (RT) aimed to improve cancer-related symptoms/provide durable local control in the non-curative setting. Mixed proton/photon plans were included. Adjacent re-irradiation (reRT) was defined as a reRT volume within the incidental dose cloud of a prior RT target, whereas direct reRT was defined as in-field overlap with prior RT target. Acute toxicity during RT until first inspection visit was graded according to the Common Terminology Criteria for Adverse Events. The Kaplan-Meier method, measured from last PIPRT fraction, was used to assess progression-free survival (PFS) and overall survival (OS). RESULTS: Eighteen patients underwent PIPRT between 2014 and 2020. Median age at treatment start was 10 years [2-21]. Median follow-up was 8.2 months [0-48]. Treatment sites included brain/spine [10], abdomen/pelvis [3], thorax [3], and head/neck [2]. Indications for palliation included durable tumor control [18], neurologic symptoms [4], pain [3], airway compromise [2], and great vessel compression [1]. Indications for protons included reRT [15] (three adjacent, 12 direct), craniospinal irradiation [4], reduction of dose to normal tissues [3]. Sixteen experienced grade (G) 1-2 toxicity; two G3. There were no reports of radionecrosis. Median PFS was 5.3 months [95% confidence interval (CI) 2.7-16.3]. Median OS was 8.3 months [95% CI 5.5-26.3]. CONCLUSIONS: The most common indication for PIPRT was reRT to provide durable tumor control. PIPRT appears to be safe, with no cases of high-grade toxicity.