Purpose: Chordoma and Chondrosarcoma are rare mesenchymal tumours occurring primarily in the axial skeleton. These slow-growing, relatively radio-resistant tumours may be associated with significant neurological morbidity. Treatment with surgical debulking and adjuvant  radiotherapy is often limited by the proximity of critical structures. We aim to present our experience treated with SRT for these tumours located in the skull base and spine.

Methods: A retrospective review was undertaken of all patients treated the senior author between 1996 and 2014. An electronic database was used to identify potential patients. Those treated with conventional radiation, those referred elsewhere or elected not to proceed with treatment were excluded.Dose fractionation regimens were converted to 2 Gy equivalent doses using an alpha/beta ratio of 2.45 to allow comparison with other series including those employing protons

Results: 22 patients met the inclusion criteria (36 patients screened). Seventeen were identified as having Chordoma (12 skull base, 3 cervical spine and 2 sacrum) and five with skull base Chondrosarcoma. The median age was 61(18-88)yrs with 12 men (54%) and 10 women (46%). Fourteen chordoma (94.1%) patients underwent  surgery prior to radiation whereas only 3 of 5 (60%) chondrosarcoma patients underwent surgery.

The median dose for chondrosarcoma  and chordoma patients treated with radical intent was 66Gy^2.45/33# and 76Gy ^2.45/38#, respectively. 

The median FU was 29 months.

Acute or late toxicity was recorded for 9 of the 15 chordoma patients (2 requiring medical treatment) and was not seen in the chondrosarcoma group. Three recurrences were seen in the chordoma group and in one chondrosarcoma patient.

Conclusion: With this small sample size and the long natural history, statements related to efficacy are necessarily limited, nevertheless the lack of toxicity is encouraging, given the higher than usual doses (up to 84Gy) delivered to the tumour bed.