OBJECT Spinal chordomas can have high local recurrence rates after surgery with or without conventional dose radiation therapy (RT). Treatment outcomes and prognostic factors after high-dose proton-based RT with or without surgery were assessed. METHODS The authors conducted a retrospective review of 126 treated patients (127 lesions) categorized according to disease status (primary vs recurrent), resection (en bloc vs intralesional), margin status, and RT timing. RESULTS Seventy-one sacrococcygeal, 40 lumbar, and 16 thoracic chordomas were analyzed. Mean RT dose was 72.4 GyRBE (relative biological effectiveness). With median follow-up of 41 months, the 5-year overall survival (OS), local control (LC), locoregional control (LRC), and distant control (DC) for the entire cohort were 81%, 62%, 60%, and 77%, respectively. LC for primary chordoma was 68% versus 49% for recurrent lesions (p = 0.058). LC if treated with a component of preoperative RT was 72% versus 54% without this treatment (p = 0.113). Among primary tumors, LC and LRC were higher with preoperative RT, 85% (p = 0.019) and 79% (0.034), respectively, versus 56% and 56% if no preoperative RT was provided. Overall LC was significantly improved with en bloc versus intralesional resection (72% vs 55%, p = 0.016), as was LRC (70% vs 53%, p = 0.035). A trend was noted toward improved LC and LRC for R0/R1 margins and the absence of intralesional procedures. CONCLUSIONS High-dose proton-based RT in the management of spinal chordomas can be effective treatment. In patients undergoing surgery, those with primary chordomas undergoing preoperative RT, en bloc resection, and postoperative RT boost have the highest rate of local tumor control; among 28 patients with primary chordomas who underwent preoperative RT and en bloc resection, no local recurrences were seen. Intralesional and incomplete resections are associated with higher local failure rates and are to be avoided.

Background. Proton therapy offers superior low and intermediate radiation dose distribution compared with photonbased radiation for brain and skull base tumors; yet tissue within and adjacent to the target volume may receive a comparable radiation dose. We investigated the tolerance of the pediatric brainstem to proton therapy and identifi ed prognostic variables. Material and methods. All patients Ͻ 18 years old with tumors of the brain or skull base treated from 2007 to 2013 were reviewed; 313 who received Ͼ 50.4 CGE to the brainstem were included in this study. Brainstem toxicity was graded according to the NCI Common Terminology Criteria for Adverse Events v4.0. Results. The three most common histologies were ependymoma, craniopharyngioma, and low-grade glioma. Median patient age was 5.9 years (range 0.5 -17.9 years) and median prescribed dose was 54 CGE (range 48.6 -75.6 CGE). The two-year cumulative incidence of toxicity was 3.8% Ϯ 1.1%. The two-year cumulative incidence of grade 3 ϩ toxicity was 2.1% Ϯ 0.9%. Univariate analysis identifi ed age Ͻ 5 years, posterior fossa tumor location and specifi c dosimetric parameters as factors associated with an increased risk of toxicity. Conclusion. Utilization of current national brainstem dose guidelines is associated with a low risk of brainstem toxicity in pediatric patients. For young patients with posterior fossa tumors, particularly those who undergo aggressive surgery, our data suggest more conservative dosimetric guidelines should be considered.

Our cohort of 174 pediatric patients with low-grade glioma demonstrated progression-free survival and overall survival rates of 84% and 92%, respectively, after proton therapy. These survival rates are similar to those of contemporary photon cohorts. Data from this prospective study inform radiation technique and overall patient management for the most common pediatric brain tumor. Purpose: Dosimetric studies show that proton therapy can reduce the low/intermediate radiation dose to uninvolved tissue in children with low-grade glioma (LGG). For this reason, LGG is the fourth most common pediatric tumor treated with proton therapy, yet clinical outcome data on efficacy and toxicity are limited. Methods and Materials: We reviewed the medical records of 174 children (21 years old) with nonmetastatic LGG enrolled on a prospective protocol and treated with proton therapy between 2007 and 2017. We assessed clinical outcomes and toxicity and analyzed patient, tumor, and treatment-related variables. Results: The median age was 10.2 years (range, 2-21). Fifty-eight percent of tumors were World Health Organization grade 1 and 30% were grade 2; 12% were diagnosed on imaging characteristics alone. The most common histology was pilocytic astrocytoma (47%). The most common tumor subsites were diencephalon/optic pathway (52%), caudal brainstem (16%), and cerebellum (13%). Forty-two percent received chemotherapy before radiation therapy. The median follow-up was 4.4 years. The 5year actuarial rates of local control, progression-free survival, and overall survival were 85% (95% confidence interval [CI], 78%-90%), 84% (95% CI, 77%-89%), and 92% (95% CI, 85%-95%), respectively. On univariate analysis, brainstem/spinal cord tumor location (62% vs 90% elsewhere) and dose <54 GyRBE (67% vs 91% for 54 GyRBE) were associated with inferior local control (P < .01 for both). Twenty-two patients (12.6%) experienced acute nausea or vomiting requiring ondansetron; 2 patients (1.1%) required corticosteroids. Serious toxicities (4% of patients)

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