Proton Beam Craniospinal Irradiation Reduces Acute Toxicity for Adults With Medulloblastoma

Purpose

Efficacy and acute toxicity of proton craniospinal irradiation (p-CSI) were compared with conventional photon CSI (x-CSI) for adults with medulloblastoma.

Methods and Materials

Forty adult medulloblastoma patients treated with x-CSI (n=21) or p-CSI (n=19) at the University of Texas MD Anderson Cancer Center from 2003 to 2011 were retrospectively reviewed. Median CSI and total doses were 30.6 and 54 Gy, respectively. The median follow-up was 57 months (range 4-103) for x-CSI patients and 26 months (range 11-63) for p-CSI.

Results

p-CSI patients lost less weight than x-CSI patients (1.2% vs 5.8%; P=.004), and less p-CSI patients had >5% weight loss compared with x-CSI (16% vs 64%; P=.004). p-CSI patients experienced less grade 2 nausea and vomiting compared with x-CSI (26% vs 71%; P=.004). Patients treated with x-CSI were more likely to have medical management of esophagitis than p-CSI patients (57% vs 5%, P<.001). p-CSI patients had a smaller reduction in peripheral white blood cells, hemoglobin, and platelets compared with x-CSI (white blood cells 46% vs 55%, P=.04; hemoglobin 88% vs 97%, P=.009; platelets 48% vs 65%, P=.05). Mean vertebral doses were significantly associated with reductions in blood counts.

Conclusions

This report is the first analysis of clinical outcomes for adult medulloblastoma patients treated with p-CSI. Patients treated with p-CSI experienced less treatment-related morbidity including fewer acute gastrointestinal and hematologic toxicities.

Introduction

Medulloblastoma is a primitive neuroectodermal tumor accounting for approximately 20% to 30% of childhood brain tumors. However, adult medulloblastoma is rare, with an incidence rate of 0.5 per million, and differs from pediatric medulloblastoma in clinical outcomes as well as its molecular profile 1, 2, 3, 4. Craniospinal irradiation (CSI), typically x-ray based (XRT), plays a critical role in management of pediatric and adult medulloblastoma, but is associated with significant acute and late side effects 5, 6, 7. These adverse effects can dramatically influence patient outcomes and quality of life (8). Proton-beam radiation therapy (PBRT) has been proposed to reduce treatment-related morbidity in patients requiring CSI. However, much of the current literature supporting proton beam CSI (p-CSI) is focused on late effects in pediatric patients and is based on risk estimates and modeling rather than actual patient data 8, 9, 10. In an effort to minimize toxicity, adults requiring CSI were treated with PBRT at the University of Texas MD Anderson Cancer Center since 2006 when PBRT became available.

The purpose of this study was to compare efficacy and acute toxicity of p-CSI versus conventional photon CSI (x-CSI) in adults with medulloblastoma. In the absence of randomized trials for this rare condition, these data can inform clinicians and patients about acute toxicities related to both p-CSI and x-CSI.