{'fraction_non_alphanumeric': 0.03837719298245614, 'fraction_numerical': 0.024671052631578948, 'mean_word_length': 4.944625407166124, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 2, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Multiple Site SBRT in Pediatric, Adolescent, and Young Adult Patients With Recurrent and/or Metastatic Sarcoma.

BACKGROUND
Stereotactic body radiation therapy (SBRT) is increasingly used for patients with recurrent and or metastatic tumors. Sarcomas are generally considered not sensitive to radiotherapy and SBRT may allow for increased biological effectiveness. We report intermediate outcomes and toxicity for pediatric, adolescent, and young adult patients treated with SBRT to sites of recurrent and or metastatic sarcoma.


PROCEDURE
We queried an Institutional Review Board-approved registry of patients treated with SBRT for metastases from pediatric sarcomas. Patients age 29 and below were assessed for local control, survival, and toxicity.


RESULTS
Thirty-one patients with a total of 88 lesions met eligibility criteria. Median patient age was 17.9 years at treatment. Sixteen patients were treated with SBRT to >1 site of disease. The median dose was 30 Gy in 5 fractions. The median follow-up time was 7.4 months (range: 0.2 to 31.4 mo). Patients were heavily pretreated with systemic therapy. In 57 lesions with >3 months of radiographic follow-up, the 6-month and 12-month local control rates were 88.3%±4.5% and 83.4%±5.5%, respectively. Radiographic local failures were rare (6/57 in-field, 4/57 marginal). Only 1/88 treated lesions was associated with a radiation-related high-grade toxicity; late grade 3 intestinal obstruction in a re-irradiated field while on concurrent therapy (gemcitabine and docetaxel). No acute grade ≥3 toxicity was observed.


CONCLUSIONS
SBRT was well tolerated in the majority of patients with favorable local control outcomes. Additional studies will be required to determine the optimal SBRT dose and fractionation, treatment volume, and appropriate concurrent therapies.