Treatment of Chordomas by Stereotactic Radiosurgery with a Linear Accelerator: Comparison with Other Modes

Abstract

This study was to determine the efficacy and safety of chordoma and chondrosarcoma treatment with CyberKnife Stereotactic Radiosurgery. Eighteen patients diagnosed with chordoma were treated with CSRS as a primary adjuvant treatment (17), or only treatment (1) for the tumor. They were followed at 6 month intervals with neurological examination, testing for pain (VAS), Quality of Life (SF-12) and MRI. Six patients were treated with other radiation modalities prior to CyberKnife: 2 patients had external beam irradiation (EBIR); 1 had proton beam radiation (PBR); 1 had EBIR and chemotherapy; 1 received heavy particle therapy (HPT) with helium ions as well as EBIR; and 1 had Gamma Knife irradiation. The series includes 28 tumor treatments for a total of 24 lesions among 18 patients with chordoma, median age 60 years (24–85 years), and 3 metastatic chordomas were treated solely with surgery. Tumor origin was weighted to the mobile spine (44 %), with 39 % intracranial and 17 % sacral. Male-to-female incidence for chordoma was 1:1. Mean tumor volume was 128.0 cm³ (12.0–457.3 cm³), median tumor radiation dose of 35 Gy (24.0–40 Gy) in five stages. Patients were followed for a median of 46 months (7–65 months) after CSRS treatment. There were 3 significant complications in patients with previous irradiation: infection in the surgical/radiation site (2), and decreased vision (1). Improvement in pain and the physical component of quality of life reached statistical significance (p.05); neurological exam was maintained throughout follow-up. Histological change included: a 10 % MIB index in a marginal recurrence; apoptosis (semi-quantitative studies underway). Seven individuals experienced recurrence at a median post-radiation interval of 10 months (5–38 months), and 4 patients presenting with disseminated tumor died 7–48 months post-therapy. Two patients demonstrated significant reduction of tumor volume (reduction from 13.4 to 2.5 cm³ at 3 years), while 9 others remained stationary with no evidence of recurrence. There has been no evidence of recurrence in one patient treated with CSRS alone (5 years), and no recurrences in spinal chordomas totally resected and irradiated with margin (37.5 Gy to the margin) with CyberKnife. Overall, the local control rate with recurrence free survival to date is 69.57 %. The CSRS safety and efficacy profile compares favorably with other treatment delivery systems. CSRS appears to reduce tumor volume with adequate dose, and the authors recommend treatment with 40 Gy in five stages to the margin of involved tissue (enhancing tumor with 1 cm margin).