Treatment outcomes of proton or carbon ion therapy for skull base chordoma: a retrospective study

Masaru Takagi,Kazuki Terashima,Masayuki Mima,Takashi Akagi,Yusuke Demizu,Yasue Niwa,Tomohiro Yamashita,Fumiko Nagano,Nobukazu Fuwa,Koh-Ichi Sakata,Kuniaki Katsui,Masaki Suga,Dongcun Jin,Osamu Fujii,Tomoaki Okimoto

doi:10.1186/s13014-018-1173-0

Abstract

BackgroundThe usefulness of particle therapy for skull base chordoma has not been established. The aim of this retrospective study was to analyse the treatment outcomes of proton therapy (PT) and carbon ion therapy (CIT) in patients with skull base chordoma at a single institution.MethodsAll patients who underwent PT or CIT with curative intent between 2003 and 2014 at Hyogo Ion Beam Medical Center were included in this study. Twenty-four patients were enrolled. Eleven (46%) received PT and 13 (54%) received CIT. Overall survival (OS), progression-free survival (PFS) and local control (LC) were calculated using the Kaplan–Meier method. Late toxicities were evaluated according to the Common Terminology Criteria for Adverse Events version 4.0.ResultsThe median follow-up was 71.5 months (range, 14–175 months). The five-year LC, PFS and OS rates were 85, 81, and 86%, respectively. The LC (P = 0.048), PFS (P = 0.028) and OS (P = 0.012) were significantly improved in patients who had undergone surgery before particle therapy. No significant differences were observed in the LC rate and the incidence of grade 2 or higher late toxicities between patients who received PT and CIT.ConclusionsBoth PT and CIT appear to be effective and safe treatments and show potential to become the standard treatments for skull base chordoma. To increase the local control, surgery before particle therapy is preferable.

Highlights

The usefulness of particle therapy for skull base chordoma has not been established
The clinical target volume (CTV) that included regions of suspected microscopic spread was generated around the gross tumour volume (GTV) by expanding three-dimensional margins of 5 mm anatomically and using manual corrections based on anatomic structures
The median follow-up was longer in the proton therapy (PT) group than in the carbon ion therapy (CIT) group (86 months vs. 56 months) without statistical significance (P = 0.902)

Summary

Introduction

The usefulness of particle therapy for skull base chordoma has not been established. The aim of this retrospective study was to analyse the treatment outcomes of proton therapy (PT) and carbon ion therapy (CIT) in patients with skull base chordoma at a single institution. 25–35% of tumours are located at the base of the skull [2] Due to their low metastasis rate of these tumours, local control (LC) is the most important indicator of patient survival [3]. Particle therapy, such as proton therapy (PT) and carbon ion therapy (CIT), have been used for skull base chordomas [11,12,13,14,15,16,17,18]. Particle therapies are considered to be able to increase local control and reduce severe late toxicities

Objectives

Methods

Results

Discussion

Conclusion