Institutional Series Validation of a Preoperative Grading System for Cranial Chordomas

Introduction: Chordomas are rare tumors of the axial skeleton arising from embryonic notochord tissue. Current standard treatment generally includes gross-total resection with adjuvant radiotherapy, though recurrence and persistence of disease remains challenging both to predict and to treat. Prior grading systems have been proposed and typically focus on elements related to surgical approach or extent. In 2017, Sekhar et al proposed a new preoperative grading system for cranial chordomas to enable tumor comparison and correlate features of clival chordoma with postoperative clinical outcomes: the Sekhar Grading System for Cranial Chordomas (SGSCC). The aim of this study is to determine utility, generalizability, and validity of this grading system through application to our institutional cohort.

Methods: This is a retrospective chart review of a single-institution tertiary care center cohort. Patients treated for clival chordoma from 1984 to 2018 are included. Collected variables include demographic information, preoperative exam, radiological findings, pathological findings, treatment details, complications, and clinical outcomes. Additional variables from the SGSCC are added to clinical data for validation, including tumor size, vascular encasement by tumor, intradural extension, brainstem involvement, and prior treatment.

Results: The current study is ongoing. Our institutional series includes 67 patients treated for clival chordoma. This cohort notably includes a larger proportion of patients treated via an endoscopic or combined approach than the original Sekhar et al cohort, which was treated largely by open approach (88%). Tumors are re-staged based on the SGSCC to determine validity of the proposed scale based on our robust institutional experience ([Table 1]). Specific staging variables undergoing analysis are tumor equivalent diameter (scale 1–4), anatomic sites involved (scale 1–9), vascular involvement (scale 0–5), intradural invasion (scale 0–2), and tumor regrowth after prior treatment (scale 0–5). These are classified into low- (score 0–7), intermediate- (score 8–12) and high-risk (score ≥ 13) grades and linked with clinical outcomes to determine utility of the preoperative grading system.

Conclusion: This study links variables from the SGSCC to existing clinical information to determine validity and generalizability of the proposed preoperative grading system. SGSCC grade has previously been correlated to completeness of resection, treatment complications, overall survival, recurrence free survival, and Karnofsky Performance Status. Application of this system to our large institutional series will help to determine whether this system is useful for clinical decision-making in a way that may guide treatment, including both surgical extent and adjuvant therapies, to ultimately impact patient outcomes.