Carbon Ion Radiotherapy for Unresectable Primary Bone Sarcoma of the Spine

Purpose/Objective(s): Primary bone sarcomas of the spine (PBSS) are rare. Common primary sarcomas include chondrosarcomas, chordoma, osteosarcoma, malignant fibrous histiocytoma (MFH), and Ewing\u27s sarcoma. Surgery remains the mainstay of treatment, although the anatomy of spine and spinal cord often limits complete surgical resection with a wide margin. Chemotherapy and radiation therapy have variable effects on these tumors. Due to the high energy transfer (LET) and the Bragg peak, carbon ion radiotherapy have been expected to be more effective and safe in the treatment for PBSS than low-LET radiation like photons. We evaluated the effectiveness and safety of carbon ion radiotherapy in patients with PBSS.Materials/Methods: From 1996 to 2006, 26 (male/female: 14/12) patients with PBSS (excluded C1-2 and sacrum primary), not suited for resection, received carbon ion radiotherapy. Ages ranged from 19 to 82 (mean 48 years). Nineteen patients had primary disease and 7 recurrent or post operative gross disease. Six tumors were located at cervical, 10 at thoracic, and 10 at lumber spine. Histologic diagnoses were as follows: chondrosarcoma in 8, chordoma in 7, osteosarcoma in 6, MFH in 2, Ewing\u27s sarcoma in 2, and angiosarcoma in 1 patients . Carbon ion radiotherapy was delivered in 16 fractions over 4 weeks. Ten patients were entered onto a phase I/II dose escalation study of carbon ion radiotherapy and the remaining 16 patients a phase II study with fixed doses. Total doses: 52.8 GyE (3.3 GyE/Fr) in 1, 57.6 GyE (3.6 GyE/Fr) in 3, 64.0 GyE (4.0 GyE/Fr) in 13, and 70.4 GyE (4.4 GyE/Fr) in 9 patients. Clinical target volumes ranged between 35 and 1232 cm3 (median 342 cm3).Results: Median survival time was 24 (range: 2-116) months for all patients and all living patients were followed more than 1 year. At 3 and 5 years, actuarial overall survival rates were 52% and 52%. Three patients experienced local recurrence, with time from carbon ion radiotherapy to local recurrence ranging from 1 to 20 months. At 3 years, actuarial local control rate was 8.6%. One grade 3 acute skin reaction and one grade 4 late skin reaction were observed. Three patients required surgical intervention for compression fracture of the affected spine at 2, 3, and 7 years after carbon ion radiotherapy.Conclusions: PBSS are rare. Local control at 3 years in patients with PBSS treated by carbon ion radiotherapy are almost similar to those in reported data on patients treated by surgical resection with/without adjuvant radiotherapy. Despite the higher doses delivered to the tumors and the locally more advanced nature of the patients in this series, toxicities were acceptable level. Carbon ion radiotherapy is suggested to be an effective and safe treatment for PBSS, but further experience and longer follow up are needed