Multicentric randomized phase II trial of gamma knife surgery (GKS) versus image-guided, intensity-modulated radiation therapy (IG-IMRT) in patients with sacrococcygeal chordoma.

Abstract

11033 Background: Chordoma is a rare slow-growing neoplasm arisen from cellular remnants of the notochord. About 30% occur in the sacrococcygeal region. Surgical resection is recommended treatment. Due to the high recurrence rate, adjuvant radiation therapy was suggested to receive as an effective method to improve local control rates. Methods: Thirty eight patients were pathologically diagnosed as non-metastatic sacrococcygeal chordoma from Aug. 2003 to May. 2015 were recruited retrospectively to analysis. All patients received surgical resection after diagnosed. Initial surgery included subtotal resection (24% of patients), and gross total resection (76% of patients). Among these patients, 25 patients treated with adjuvant IG-IMRT, while 13 patients treated GKS after surgical resection. The median follow-up was 40 months (range, 6–151 month) for all patients, The PTV of IG-IMRT group received total doses were 60 Gy (range, 56-74Gy), delivered with 2-2.2 Gy/fraction, while GKS group underwent a total of 6-8 sessions treatment. Results: For the IG-IMRT group and the GKS group, the 5-year overall survival and local control rates were 87.5% and 67.7%, respectively. And 5-year local control rates were 35% and 22.2%, respectively. In total, 18 patients progressed locally: 11 were in the IG-IMRT group and 7 in the GKS group. In comparison with GKS group, the IG-IMRT group has a better overall recurrence-free survival (p = 0.03), the significance remained after adjusted for surgery results, age and gender. Moreover, there is no significant difference of overall survival was found between these two groups. Conclusions: We report favorable local control and adverse event rates following IG-IMRT, and suggested IG-IMRT is the first choice of adjuvant radiation therapy for sacrococcygeal chordoma treatment.