Maximum surgical resection and adjuvant intensity-modulated radiotherapy with simultaneous integrated boost for skull base chordoma

Background: Local recurrence is common after surgical resection of clivus chordoma. We report the results of maximum surgical resection followed by intensity-modulated radiotherapy with simultaneous integrated boost (IMRT-SIB). Methods: We reviewed 14 consecutive clivus chordoma cases undergoing postoperative IMRT-SIB using the institutional protocol between 2005 and 2013. Total and near-total resections were achieved in 11 patients (78.6 %), partial in 2 patients (14.3 %), and 1 patient (7.1 %) received RT for recurrent tumor after total resection. Gross residual or the high-risk area defined the planning target volume (PTV)1; PTV2 was the postoperative tumor bed plus a 3–5-mm margin, and PTV3 was PTV2 plus a 5–10 mm margin. A moderate hypofractionation schedule was used: doses to PTV1, PTV2 and PTV3 were 3.9 Gy, 3.15 Gy and 2.8 Gy through 15 fractions for the first two patients, and the rest received 2.5 Gy, 2.2 Gy and 1.8 Gy through 25 fractions. The biologically equivalent dose in 2-Gy fractions (EQD2) was 65–68 Gy for PTV1, 52–56 Gy for PTV2, and 44.3–44.8 Gy for PTV3. Results: Median follow-up was 41 months. Eight patients were free of disease for median 42.5 months (range 23–91 months), four patients had stable disease for median 60.5 months (range 39–113 months), and 1 patient showed partial response for 38 months after RT. Local progression was seen in one patient who received EQD2 67.8 Gy after partial resection. Estimated 5-year progression-free and overall survival rates were 92.9 %. Surgery improved the neurologic deficit in six patients, and IMRT-SIB was well tolerated without lasting toxicity. Conclusion: Our experience suggests that maximum resection and high-dose IMRT-SIB can achieve local control without significant morbidities.