Radiotherapy for Adult Medulloblastoma: Evaluation of Helical Tomotherapy, Volumetric Intensity Modulated Arc Therapy, and Three-Dimensional Conformal Radiotherapy and the Results of Helical Tomotherapy Therapy

Received Oct 18, 2017; Revised Jan 30, 2018; Accepted Feb 19, 2018

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1. Introduction

Medulloblastoma (MB), which can spread through the cerebrospinal fluid, is a malignant primitive neuroectodermal tumor that originates from the posterior cranial fossa (PCF). A total of 80% of medulloblastoma patients are diagnosed when they are younger than 15 years of age (median age, 5 years) [1]. The incidence of adult medulloblastoma (AMB) is approximately 0.5/100000 [2, 3], accounting for 0.4–1% of adult nervous system tumors [4]. Surgery is the first treatment choice for nonmetastatic MB, and all patients should be treated with craniospinal irradiation (CSI) postoperatively. Because of the long irradiation range, multiple radiation fields must be designed for conventional radiotherapy technology. It is difficult to abut adjacent radiation fields. CSI can be completed in only one session with helical tomotherapy (HT) [5–8], which is convenient for clinical practice.

This study retrospectively analyzed the treatment results of 5 cases of AMB treated with HT at Zhejiang Cancer Hospital. After that we completed the volumetric intensity modulated arc therapy (VMAT) and three-dimensional conformal radiotherapy (3D-CRT) plan retrospectively and evaluated the dose of HT, VMAT, and 3D-CRT.

2. Methods

2.1. General Information

Five AMB patients (18 years of age and older) who were confirmed by pathology and treated with HT from June 2015 to October 2016 at Zhejiang Cancer Center were enrolled in the study. The Chang staging system [9] was used to evaluate the patients. Acute toxicity was evaluated with Common Toxicity Criteria (CTC) V4.0, and the last follow-up time was in January 2018. Patients were immobilized by the head, neck, and shoulder, and they wore body thermoplastic masks. CT-simulation equipment was used (i.e., Philips Brilliance CT or GE Light Speed), and the scanning range was from the top of the head to the ossa sedentarium. The simulation images were transmitted to an Accuray CT Planning Station Hi-Art Version 5.1.0 workstation, RayStation 4.0V, and Pinnacle Version 9.2 workstation.

2.2. Target Definition and Prescription Dose

The brain, spinal cord, PCF, and organs at risk (OAR) were contoured on the simulation CT images layer...