Correlation of acute and late brainstem toxicities with dose-volume data for pediatric patients with posterior fossa malignancies

Publication date: Available online 19 March 2017
Source:International Journal of Radiation Oncology*Biology*Physics
Author(s): Ronica H. Nanda, Rohit G. Ganju, Edward Schreibmann, Zhengjia Chen, Chao Zhang, Naresh Jegadeesh, Richard Cassidy, Claudia Deng, Bree Eaton, Natia Esiashvili
PurposeRadiation-induced brainstem toxicity after treatment for pediatric posterior fossa (PF) malignancies is incompletely understood, especially in the era of intensity-modulated radiation therapy (IMRT). The rates of and predictive factors for brainstem toxicity after photon radiation therapy (RT) for PF tumors were examined.Materials/MethodsAfter IRB approval, 60 pediatric patients treated at our institution for non-metastatic infratentorial ependymoma and medulloblastoma with IMRT were included in this analysis. Dosimetric variables, including mean and maximum dose to the brainstem, dose to 10-90% of the brainstem (in 10% increments), and the volume of brainstem receiving 40, 45, 50, and 55 Gy were recorded for each patient. Acute (onset within 3 months) and late (beyond 3 months of RT completion) RT-induced brainstem toxicities with clinical and radiographic correlates were scored using CTCAE version 4.0.ResultsPatients from ages 1.4-21.8 years were treated using IMRT or VMAT postoperatively to the posterior fossa or tumor bed. At a median clinical follow up time of 2.8 years, fourteen patients developed symptomatic brainstem toxicity (crude incidence 23.3%). There was no correlation between the dosimetric variables examined and brainstem toxicity. Vascular injury or ischemia strongly trended toward predicting brainstem toxicity (P=0.054). Patients with grade 3-5 brainstem toxicity were treated to significant volumes of the posterior fossa.ConclusionThis series demonstrates a low but not negligible risk of brainstem radiation necrosis for pediatric patients with posterior fossa malignancies treated with intensity-modulated radiation therapy. No specific dose-volume correlations were identified but modern treatment volumes may help limit severe toxicity. Additional work investigating inherent biologic sensitivity may also provide further insight into this clinical problem.

Teaser

The rates of brainstem toxicity and dosimetric factors for children treated with intensity-modulated radiation therapy for posterior fossa CNS malignancies remain unclear. Our series demonstrates a very low rate of severe brainstem toxicity in these patients, with severe toxicities limited to children irradiated to large volumes of the posterior fossa. Limiting the volume of the brainstem and posterior fossa irradiated may limit significant brainstem toxicities.


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