Brainstem toxicity after proton or photon therapy in children and young adults with localized intracranial ependymoma: A French retrospective study.

in Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology by Céline Dalmasso, Claire Alapetite, Stéphanie Bolle, Farid Goudjil, Amélie Lusque, Jacques Desrousseaux, Line Claude, Jérome Doyen, Valérie Bernier-Chastagner, Anne Ducassou, Annick Sevely, Margaux Roques, Fatima Tensaouti, Anne Laprie

TLDR

  • The study looked at the difference between two types of radiation therapy (proton therapy and photon therapy) for a type of brain tumor called ependymoma. The study found that there was no difference in the number of people who got brainstem injury from the two types of radiation therapy. However, the study did find that some people got changes in their brain that didn't cause any symptoms, but could be seen on a scan. This happened in 4.8% of people with ependymoma. The study also found that there was no relationship between the amount of radiation therapy or the type of radiation therapy and the changes in the brain that didn't cause any symptoms.

Abstract

Ependymoma is the third most frequent childhood braintumor. Standard treatment is surgery followed by radiation therapy including proton therapy (PBT). Retrospective studies have reported higher rates of brainstem injury after PBT than after photon therapy (XRT). We report a national multicenter study of the incidence of brainstem injury after XRT versus PBT, and their correlations with dosimetric data. We included all patients aged < 25 years who were treated with PBT or XRT for intracranial ependymoma at five French pediatric oncology reference centers between 2007 and 2020. We reviewed pre-irradiation MRI, follow-up MRIs over the 12 months post-treatment and clinical data. Of the 83 patients, 42 were treated with PBT, 37 with XRT, and 4 with both (median dose: 59.4 Gy, range: 53‑60). No new or progressive symptomatic brainstem injury was found. Four patients presented asymptomatic radiographic changes (punctiform brainstem enhancement and FLAIR hypersignal), with median onset at 3.5 months (range: 3.0‑9.4) after radiation therapy, and median offset at 7.6 months (range: 3.7‑7.9). Two had been treated with PBT, one with XRT, and one with mixed XRT-PBT. Prescribed doses were 59.4, 55.8, 59.4 and 54 Gy. Asymptomatic radiographic changes occurred in 4.8% of patients with ependymoma in a large national series. There was no correlation with dose or technique. No symptomatic brainstem injury was identified.

Overview

  • The study aimed to compare the incidence of brainstem injury after proton therapy (PBT) versus photon therapy (XRT) in patients with intracranial ependymoma aged <25 years at five French pediatric oncology reference centers between 2007 and 2020. The study included 83 patients, with a median dose of 59.4 Gy, range: 53-60. The primary objective was to determine if there was a correlation between dosimetric data and the incidence of brainstem injury after radiation therapy. The study found no new or progressive symptomatic brainstem injury and four patients presented asymptomatic radiographic changes with median onset at 3.5 months after radiation therapy. The study also found that asymptomatic radiographic changes occurred in 4.8% of patients with ependymoma in a large national series. There was no correlation with dose or technique.

Comparative Analysis & Findings

  • The study compared the outcomes observed under different experimental conditions or interventions, specifically the incidence of brainstem injury after PBT versus XRT. The study found no new or progressive symptomatic brainstem injury and four patients presented asymptomatic radiographic changes with median onset at 3.5 months after radiation therapy. The study also found that asymptomatic radiographic changes occurred in 4.8% of patients with ependymoma in a large national series. There was no correlation with dose or technique.

Implications and Future Directions

  • The study's findings suggest that there is no significant difference in the incidence of brainstem injury between PBT and XRT in patients with intracranial ependymoma. The study also highlights the importance of monitoring for asymptomatic radiographic changes after radiation therapy. Future research could focus on identifying factors that may increase the risk of symptomatic brainstem injury and developing interventions to mitigate this risk. Additionally, further studies could explore the use of novel techniques, such as magnetic resonance-guided focused ultrasound (MRgFUS), as an alternative to radiation therapy for ependymoma.
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