Extent of Resection in Glioblastoma: Incorporating IDH Status and Clinical Factors to Predict Outcome
Abstract
Background: The benefits of increasing extent of resection (EOR) for both overall survival and progression-free
survival(PFS) in glioblastoma has been well documented. However, models predicting surgical outcomes have failed to
incorporate a patient’s IDH status, a known prognostic factor.
Objective: We isolate the impact of IDH and the interaction between IDH and tumor volume while adjusting for known
prognostic variables. Both overall survival and time to progression-free survival (PFS) are analyzed.
Methods: We performed a retrospective cohort study of 98 patients with glioblastoma who had undergone either biopsy or
surgical resection. Tumor volumes were determined by volumetric analysis. Univariable and multivariable Cox PH
Regression models were built using overall survival and PFS as endpoints.
Results: Increasing EOR and decreasing residual tumor volume (RTV) were both associated with prolonged overall
survival and PFS. When IDH status was added to multivariable models, the model utilizing RTV provided a slightly better
fit compared to EOR. An interaction term between RTV and IDH status was characterized, such that at low RTVs the
prognosis of an IDH mutant is significantly better than that of an IDH wild-type, an effect that is less important as RTV
increases. The significance of this term was confirmed by improved fit upon insertion into multivariable models .
Conclusion: Minimizing RTV and increasing EOR are important prognostic factors for both IDH wild-type and IDH mutant
glioblastoma. The protective benefit of the IDH mutation at lower RTVs suggests these patients are the best candidates for
aggressive surgical resection.