Article
Spot-scanning proton radiation therapy for extra-cranial chordoma
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Published: | September 24, 2009 |
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Background: Extra-cranial chordomas (ECC) require high dose radiotherapy to achieve local control (LC). Tumor proximity to critical Organs at risk poses significant dose constraints. Proton-Radiotherapy (PT) has been employed at the Center for Proton Radiation Therapy at Paul Scherrer Institue (PSI).
Material and methods: Between 1999–2005, 40 patients with Chordoma of C-, T-, L-spine and Sacrum underwent PT. Eighteen patients had gross residual disease deemed not to be amenable to further resection (GTV, range: 13–495 ml). Twenty-one patients had undergone prior surgical stabilization (SS) of the axial skeleton. Median total dose was 72 Gy. Median follow-up time was 43 months.
Results: At 5 years, overall LC rate was 62%. One failure occurred in 19 patients without SS after 6 years, resulting in actuarial LC rate at 5 years of 100%. Twelve failures were diagnosed in 21 patients with SS, yielding a 5 year LC rate of 30% (p=0.0003). Five-year OS for the entire cohort was 80%. Differences in LC did not yet impact on OS. No high grade neurotoxicity was observed.
Conclusion: Spot scanning based PT at PSI delivered subsequently to function-preserving surgery is safe and highly effective in ECC patients without major surgical instrumentation. Results of a reduced LC rate in patients with SS prompted a detailed cause-analysis. This investigation is currently still in progress.