Skull Base Chordoma and Chondrosarcoma: Changes in National

1. Skull Base Chordoma and Chondrosarcoma: Changes in National Radiotherapy Patterns and Survival Outcomes Henry S. Park, MD, MPH; Kenneth B. Roberts, MD; James B. Yu, MD Department of Therapeutic Radiology, Yale University School of Medicine BACKGROUND Table 2: Multivariate logistic regression analysis identifying predictors of gross total resection and radiation therapy utilization. Table 1: Demographic and clinical information of patients receiving RT vs. those not receiving RT. • Skull base chordoma and chondrosarcoma are rare tumors that arise from embryonic remnants along the neuroaxis. • Indolent course typical, but local recurrences common despite maximal surgical resection and high-dose radiotherapy (RT), especially in skull base. • Single-institution retrospective evidence indicates that proton beam radiotherapy (PBRT) may improve long-term outcomes, but meta-analyses do not conclusively demonstrate progression-free survival or overall survival benefit for PBRT. • We sought to assess the evolving role of RT and its effect on survival of skull base chordoma and chondrosarcoma. METHODS • Study design: Retrospective cohort analysis using prospectively collected data from the National Cancer Institute’s Surveillance Epidemiology, and End Results (SEER) database, which captures ~28% of all U.S. cancer diagnoses. • Subjects: 376 adult patients with histologically-diagnosed chordoma not otherwise specified (NOS) [ICD-O-3 code 9370], chondroid or dedifferentiated chordoma [9371, 9372] or chondrosarcoma [9220, 9221, 9230, 9240, 9242, 9243] located in the bones of the skull or face (C410) diagnosed from 1988-2008. • Statistical Analysis: Chi-square tests, Wilcoxon rank sum test, logistic regression analysis, Kaplan-Meier analysis, and Cox proportional hazards model analysis. Table 3: Cox proportional hazards model identifying predictors of overall survival. Figure 1: Kaplan-Meier survival curves by (A) year of diagnosis and (B) histology. A RESULTS • Among 57% of patients who underwent surgical resection, 42% received gross total resection (GTR). • RT was utilized in 46% of patients overall and in 45% of patients following GTR. • Utilization of surgical resection or RT was not significantly different by sex, race, diagnosis year, or histology on univariate or multivariate analysis. • After adjustment, patients ≥ 65 years were less likely to receive GTR (OR 0.39, p=0.018) and more likely to receive RT (OR 1.75, p=0.048). • After adjustment, diagnosis after 2001 (HR 0.42, p=0.002) and chondrosarcoma histology (HR 0.47, p=0.003), but not surgical extent or RT utilization, were associated with improved survival. CONCLUSIONS Log-rank p < 0.001 • On a national scale, overall survival from skull base chordoma and chondrosarcoma has improved significantly over time, though rates of surgical resection and RT have not increased over time. • Older patients less likely to receive GTR and more likely to receive RT. • Lack of association between GTR/RT utilization and improved survival may be confounded by unmeasured variables. • Future research is needed to evaluate potential determinants of this improved survival, including PBRT utilization, imaging technology, surgical technique, and supportive care. B Log-rank p < 0.001 For reprints, please contact: Henry Park, henryspark@gmail.com