1. Proton Therapy for Chondrosarcomas of the Skull Base and Cervical Spine: Long-term Experience at Loma Linda University Medical Center D. Y. Kim 2, R. W. Schulte 1, L. N. Loredo 1, J. D. Slater 1, J. M. Slater 1 1 Department of Radiation Medicine, Loma Linda University Medical Center 2 Research Institute and Hospital, National Cancer Center, Goyang, Republic of Korea

2. Background & Purpose Chondrosarcomas of the Skull Base and Cervical Spine »rare tumors arising from skeletal bone often adjacent to critical neural structures »locally aggressive, but rarely metastatic »most are low or intermediate grade »historically considered to be radioresistant tumors »evolved as indication for high dose fractionated proton/heavy ion therapy during the 1980s »most published series combined chondrosarcomas with chordomas »this is a report on our single-institution experience with proton therapy of chondrosarcoma of the skull base and the cervical spine

3. Materials & Methods »63 patients with non-metastatic chondrosarcoma (June1992 – May 2004) ~Base of skull55 (87.3%) ~Cervical spine 8 (12.7%) ~Male 32 (50.8%) ~Female31 (49.2%) »Median age 43 years (18 – 78 years) »Mean follow-up 84 months (19 – 171 months) »Surgery ~Gross total resection 17 (27.0%) ~Subtotal resection 43 (68.2%) ~Biopsy only 3 ( 4.8%) »Proton treatment (60 pats protons only, 3 pats photons & proton boost) ~Median dose72.0 GyE (RBE = 1.1) (63.0 – 79.2 GyE) ~1.8 Gy/fraction & 5 fractions per week ~Dose constraints/OAR: brainstem ( max. dose < 64 GyE surface, <54 GyE center), Optic chiasm & nerves (max dose < 60 GyE)

4. Results »Local Control and Overall Survival ~9 patients with local failure, 5 died of local progression ~Median time to failure 17 months (8-60 months) ~5- & 10-year local control rates 86.3% and 83.1%, respectively ~5- & 10-year overall survival rates 92.9% and 76.9%, respectively ~Cervical spine location only significant factor for local progression »Late Radiation Toxicity Grade ≥2 (CTCAEv3) ~Otitis media12.7% ~CNS changes in MRI12.7% Grade >3 4.8% ~Hypopituitarism11.1% ~Hearing loss 3.2% ~Cognitive deficits 4.8%

5. Conclusions »Chondrosarcomas can be successfully treated with surgery followed by postoperative high-dose proton therapy to a dose of ~72 GyE »Cervical spine location is associated with poor local control »Late complication rates similar to other series of high- dose proton therapy of base of skull tumors