Preliminary Result of Hyperfractionated High-Dose Proton Beam Radiotherapy for Pediatric Skull Base Chordomas

Abstract

Objective: Proton beam therapy (PBT) may provide good local control for skull base chordoma and reduced toxicities, especially for pediatric patients. Methods: We evaluated the efficacy and safety of hyperfractionated high-dose PBT in6 pediatric patients with newly-diagnosed skull basechordoma who were treated with PBT at our institute from 2011 to 2015. The patients were 5 males and one female, and the median age was 9 years old (range: 5 -13). All patients received surgery before PBT. The median period between surgery and PBT was 57 days (range: 34 -129 days). The treatment dose was 78.4 GyE in 56 fractions (twice per day). Results: All patients received PBT without severe acute toxicity. The median follow-up period was 27 months (range: 21 -71 months). At the last follow-up, all patients were alive and all tumors were well controlled. Acute and late toxicities were generally acceptable, with only grade 1 and 2 events. Late toxicities included growth hormone abnormality and cortical hormone abnormality. One patient needed growth hormone and cortical hormone replacement therapy. Conclusion: Although the number of pediatric patients was small, our overall findings in the 6 cases indicate that hyperfractionated high-dose PBT is safe and effective for pediatric patients with skull base chordoma.

Risk Factors for Radiation Necrosis and Local Recurrence after Proton Beam Therapy for Skull Base Chordoma or Chondrosarcoma

“…In multivariate analysis, tumor maximum diameter and pathology were significant factors associated with local recurrence. Previous studies have shown that chordoma has more local recurrence than chondrosarcoma [3,13,14]. In a multicenter study of Gamma-knife treatment of 16 Gy (median) for 51 postoperative (n = 30) or recurrent (n = 21, 41%) chondrosarcomas, Kawashima et al achieved good 3-, 5-and 10-year posttreatment local control rates of 87%, 78% and 67%, respectively [33].…”

“…Skull base chordoma accounts for 0.5% of primary brain tumors and chondrosarcoma accounts for 0.1% in Japan [1]. The standard treatment for skull base chordoma or chondrosarcoma is tumor resection [2,3]. However, due to the complexity of the anatomy of the base of the skull, it is difficult to completely remove the tumor with a sufficient margin.…”

The role of particle radiotherapy in the treatment of skull base tumors

“…Protons and heavy ions, such as carbon ions, can potentially improve dose sparing of normal tissues through the exploitation of the Bragg peak phenomenon, resulting in an increase in energy deposition with penetration depth up to a sharp maximum followed by a rapid decrease at the end of the penetration range ( 3 ). These features permit more precise and conformal dose localization to the target compared with conventional photon RT ( Figure 1 ).…”