76. High dose radiation therapy improves survival for chordoma patients with positive surgical margins

Abstract

BACKGROUND CONTEXT The role of radiation therapy (RT) for the treatment of axial chordomas remains controversial. Previous large database reviews have not found adjunct RT to improve overall survival, but these studies did not stratify based on high/low dose RT, the modality of RT, or the patient's surgical margin status. PURPOSE We investigated the National Cancer Database (NCDB) to determine if high dose RT improves survival in patients with positive vs negative surgical margins. Additionally, the study compares the 5-year survival between patient's treated with high vs low dose RT and advanced vs conventional delivery methods. STUDY DESIGN/SETTING Retrospective study. PATIENT SAMPLE A total of 1,480 chordoma patients. OUTCOME MEASURES Five-year overall survival. METHODS A total of 1,480 patients were identified in the NCDB between 2004 and 2015 with a histologically confirmed axial chordoma. Survival analysis was performed using the Kaplan Meier method. The 5-year survival was compared between surgical resection alone and surgical resection and adjunct therapeutic RT for the overall cohort, patients with positive surgical margins, and patients with negative surgical margins. Therapeutic RT was defined as a radiation dose greater than 65Gy. For patients treated with RT, the 5-year survival was compared between palliative dose ( 65Gy) RT. Similarly, 5-year survival was compared between proton beam therapy (PBT), stereotactic radiosurgery (SRS), intensity-modulated radiation therapy (IMRT), and conventional external beam radiation therapy (EBRT). A multivariable analysis was performed to determine independent prognosticators associated with 5-year overall survival. RESULTS The cohort included 1,480 chordoma patients; skull base (n=569), sacral (n=551), mobile spine (n=360). The 5-year survival for the entire cohort was 76%. The survival for patients treated with surgical resection and adjunct therapeutic RT was greater than surgery alone (85% vs 80%, p=0.04). Therapeutic adjunct RT improved survival compared to surgery alone in the setting of positive surgical margins (82% vs 71%, p=0.03). In the setting of negative surgical margins adjunct RT did not statistically improve survival (p=0.33). Radiation dose >65Gy improved survival when compared to radiation dose between 40-65Gy (85% vs 69%, p CONCLUSIONS Adjunct RT (dose >65Gy) was associated with improved survival for patients with positive surgical margins; however, a survival benefit was not observed for patients with negative surgical margins. High dose RT and advanced radiation techniques, specifically PBT, were associated with improved 5-year survival. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.