Volumetric Analysis of Extent of Resection, Survival, and Surgical Outcomes, for Skull Base Chordomas

Background Skull base chordomas are aggressive primary bone neoplasms that often originate from the residual embryonic notochord located in the skull base. These tumors make up 1 to 4% of the primary malignant bone tumors and occur in 0.02 in 100,000 people per year. For skull base chordomas, the median survival is 6.29 years, with a 5-year progression-free survival (PFS) of 50.8%. The standard of care for these lesions involves maximal surgical resection followed by radiation treatment. However, to date, there is no literature that statistically evaluates the role of volumetrically calculated extent of chordoma tumor resection on prognosis. This study evaluates the role of volumetrically analyzed extent of resection on PFS and determines predictors that influence the surgical extent of resection.

Methods Twenty-three patients who had undergone an endoscopic endonasal resection of a skull base chordoma from 2008 to 2016 were analyzed. Pre- and postoperative tumor volumes were calculated based on the T2 MRI imaging and the extent of resection was calculated utilizing OsiriX software. Kaplan–Meier curves and linear regression modeling were implemented to evaluate the role of EOR on PFS as well as to determine predictors that significantly influenced the extent of resection for skull base chordomas.

Results The mean EOR was 80.7%. The median preoperative tumor volume was 14.6 cm³ (range: 0.41–68.4). Complete 100% resections were seen in 12 (52.2%) of cases. EOR of 100% was found to have a significantly better PFS compared with EOR <100 (p = 0.037, [Fig. 1]). Interval increases in EOR did not show significant differences in PFS when comparing EOR <70 to EOR 70–99 (p = 0.114, [Fig. 2]). Factors that were significantly associated with EOR in the univariate linear regression model were gender, tumor diameter, preoperative tumor volume, and intradural tumor invasion, while only intradural invasion was significant in the multivariate model (Table 1).

Fig. 1 Kaplan–Meier curve of EOR 100 vs. <100% on PFS.

Fig. 2 Kaplan–Meier curve depicting interval EOR on PFS.

Table 1 Linear regression model of variables affecting extent of resection

Conclusion A complete 100% resection of a skull base chordoma may provide improved PFS for chordoma patients. Tumor size, gender, tumor histology, and specific bony invasion were not significant predictors of EOR, while intradural invasion of the tumor can limit the extent of resection. Although maximal resection may improve PFS, careful surgical planning with a thorough evaluation of the tumor anatomy must be implemented to provide safe and effective surgical management.