Preliminary experience in treating skull base chordomas with high-dose hyperfractionated stereotactic photon radiation therapy
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Skull base chordomas (SBC) are characterized by persistent progression. Conventional radiation following resection increases 5- and 10-year local control (LC) to 36 and 23 %, respectively. Patients treated with protons result in 10-year LC of 50 %. Brainstem dose constraints have inhibited higher prescription doses with photons. We reviewed our experience using high-dose fractionated stereotactic photon radiation therapy (HD-FSRT) to 81 Gy for SBC.
We reviewed patients diagnosed with SBC and treated with radiation from 1999 to 2010. We excluded those with metastatic disease and prior radiation. Dose distributions and target volumes were obtained from radiation records.
Twelve patients met the search criteria. Median dose was 81 Gy (76.8–82.5) using a hyperfractionated regimen. Eleven patients with available data had median max and mean doses to the brainstem of 81 Gy (46.7–85.7) and 38 Gy (6.6–58.1). Mean target volume was 22 cm3 (5.3–193. 3). LC at 3 and 5 years was 69 and 46 %. Overall survival was 90 and 68 % with a mean follow-up of 55 months. There was a trend for improved LC in patients treated adjuvantly.
HD-FSRT can achieve comparable doses to proton therapy plans, and preliminary results are an improvement from conventional photon therapy.