Influence of Fluorescence-guided Resection with 5‑aminolevulinic Acid on Surgical Outcomes, Extent of Resection, and Survival in Subventricular Zone Glioblastoma

Introduction: 5-aminoleulinic acid (5-ALA) is an important tool to guide resection of glioblastoma (GBM). However, in the ventricular wall, there may be visible fluorescence in response to 5-ALA even in the absence of tumor cells. This may impact the surgical decision to continue resection into the ventricles in subventricular zone (SVZ) GBM cases. The aim of this study was to determine the clinical implications of fluorescence-guided resection (FGR) of SVZ GBM.

Methods: The electronic medical records of adult patients with newly diagnosed SVZ GBM were retrospectively reviewed. Different parameters were compared between patients resected under fluorescence guidance (FGR group) or white light only (WL group), overall and within subgroups defined by known prognostic factors.

Results: Compared to the WL group (n=46), the FGR group (n=48) were characterized by lower postoperative tumor volume (3.97±6.92cm3 vs. 7.21±6.81cm3, p=0.038), greater extent of resection (90.91±12.9% vs. 81.19±17.69%, p=0.005), and higher rates of gross total resection (GTR) (28.6% vs. 11.6%; OR=0.296, 95% CI 0.0968 to 0.9057; p=0.0329). They also had higher rates of intraoperative ventricular entry (72.9% vs. 42.2%, p=0.003), and shunt placement (by >2.5-fold, p=0.199). GTR showed a trend-level association with increased 1-year overall survival (OS) (HR=0.308, 95%CI 0.073-1.3, p=0.089). When compared to the entire cohort, FGR was significantly associated with increased OS for the subgroups of patients < 55 years (HR=0.489, p=0.026), patients treated with Stupp protocol (HR=0.562, p=0.0086) and patients with KPS >70 (HR=0.428, p=0.00049). Such significant differences were not demonstrated for any of the WL subgroups.

Conclusion : FGR using 5-ALA had a significant favorable impact on extent of resection and residual tumor in patients with SVZ GBM. These positive effects associated with FGR appeared to outweigh its association with increased rates of ventricular entry and shunt surgery, which had no meaningful impact on most outcomes. In patients with favorable prognostic parameters, FGR and GTR were associated with clinically meaningful improved OS.