Carbon Ion Radiotherapy for Chondrosarcoma

Purpose: Chondrosarcoma is the second most frequent primary malignant bone tumor. Surgery has been considered as the main form of treatment for chondrosarcoma, and the definitive en bloc resection of tumor is mandatory to obtain long term disease free survival. However, radical surgical resection is often difficult in patients with chondrosarcoma of the trunk and photon radiotherapy is not useful for chondrosarcoma because of radioresistant tumor. Due to the high linear energy transfer (LET) and the Bragg peak, carbon ion radiotherapy has been expected to be more effective and safe in the treatment for chondrosarcomas than low-LET radiation like photons. The aim of this study is to evaluate the effectiveness and safety of carbon ion radiotherapy for chondrosarcoma not suited for surgical resection.\nMethods: From June 1996 to December 2009, 78 lesions of 75 (male/female:43/32) patients with chondrosarcoma (excluded skull base primary) received carbon ion radiotherapy. They had no metastases and determined to be unresectable by the referring surgeons. In this series, 5 patients who refused surgery were included. Ages ranged from 17 to 82 years (median 56). Sixty patients had primary disease and 15 patients with recurrent disease after surgery. Histologic grades of the 78 lesions were as follows: grade 1 in 11, grade 2 in 47, grade 3 in 4, dedifferentiated in 3, mesenchymal in 5 patients, and 8 in not specified their grade. There were 54 pelvic (38 iliac, 14 sacral, and 2 pubic) lesions, 6 thoracic spine, 5 lumber, 5 rib, 4 cervical, 2 scapula, 1 femur, and 1 fibula. Carbon ion radiotherapy was delivered in 16 fractions over 4 weeks. Total doses: 57.6 GyE (3.6 GyE / Fr) in 2, 64.0 GyE (4.0 GyE / Fr) in 7, 70.4 GyE (4.4 GyE / Fr) in 66, and 73.6 GyE (4.6 GyE / Fr) in 3 lesions. Clinical target volumes ranged between 25 and 2900 cm3 (median 496 cm3). \nResults: The median follow up was 41 (range: 3-117) months for all patients and all living patients were followed more than 2 years. At 5 years, actuarial local control (LC) rate and overall survival (OS) rate were 55% and 57%, respectively. In patients with smaller target volume (<400cm3), 5-year LC rate and OS rate were 76% and 73%, respectively. There were significant differences in LC and OS between smaller and larger target volume group (p