Counseling Patients with a Glioblastoma Amenable Only for Subtotal Resection: Results of a Multicenter Retrospective Assessment of Survival and Neurologic Outcome

Background: Patients with a glioblastoma (GB) amenable only for subtotal resection (STR) represent a challenge in patient counseling. Our objective was to assess impact of extent of resection (EoR) on survival and clinical outcome of these patients.

Methods: We performed a retrospective multicenter assessment. Patients receiving an intended STR in 3 centers with unilocular, primary, highly eloquent GB who received the same adjuvant treatment were included. We assessed EoR, neurologic outcome, and rate of complications. Progression-free survival (PFS) and overall survival (OS) were calculated with Kaplan-Meier estimations. We used 1% EoR and 1-cm³ steps to detect a threshold for a minimal EoR and residual tumor volume (RV) to be beneficial for survival and performed multivariate Cox regression models to assess its influence on PFS and OS.

Results: In total, 67 patients were included. EoR and RV were not significantly associated with PFS in multivariate Cox regression. Multivariate Cox regression model for OS revealed that volumetric EoR is a significant predictor for OS (P = 0.002, OR 0.982), same as RV (P = 0.007, OR 1.03), controlling for age, preoperative tumor volume, sex, and recurrent surgery. We found a significant benefit for OS if an EoR >60% or a RV <8 cm³ was reached. In the aforementioned multivariate Cox regression models, an EoR ≤60% and a RV ≥8 cm³ independently showed a significantly negative association with OS (P = 0.044, OR 1.96/P = 0.024, OR 2.07).

Conclusions: In highly eloquent GB, EoR significantly matters for patients' OS. Also, potential RV should be considered when treating these patients. In cases with an expected RV above or an EoR below the aforementioned thresholds, open surgery should be carefully considered.