Impact of post-operative DWI rim restriction following resection of newly diagnosed glioblastoma

Introduction: A frequently observed phenomenon seen on early post-operative MRI scans of the glioblastoma (GBM) patients is the appearance of a rim of diffuse restriction around the surgical cavity on diffusion weighted imaging (DWI). The main objective of this study is to explore the natural history of these peritumoral DWI abnormalities and their impact on short- and long-term neurological outcomes in newly diagnosed GBM.

Methods: We conducted a retrospective cohort analysis of 304 patients who underwent initial resection for newly diagnosed IDH wild-type GBM at the University of California, San Francisco (UCSF) between January 01, 2017 and August, 31 2021. Postoperative DWI rim restrictions were classified into six categories based on severity: 0 = no rim restriction, 1 = minimal rim restriction, 2 = moderate rim restriction, 3 = minimal region or sector ( < 1 cm³) of restriction, 4 = moderate region or sector (>1 cm³) of restriction, 5 = significant infarct.

Results: Of the 304 patients analyzed, 187 (61.5%) exhibited post-operative DWI rim-restriction (graded as DWI 2-5), while 111 patients (38.5%) showed minimal or no restriction (classified as DWI 0-1). In our cohort, all post-operative DWI abnormalities resolved within six months, irrespective of the initial severity.
Among the 42 patients (13.8%) who developed new immediate postoperative deficits, 25 (59.5%) had DWI rim restriction (Grades 2–5). The presence or grade of DWI alterations was not significantly associated with immediate postoperative deficits (p = 0.86) or recovery at three months (p = 0.51). However, higher DWI grades (2–5) were associated with worse overall survival (OS) in patients under 65 years (p = 0.02). Subgroup analysis also showed higher DWI grades and lower extent of resection (EOR) were independent predictors of the outcome (p = 0.04).

Conclusion : Initial appearance and severity of post-operative DWI abnormalities does not directly predict a new post-operative deficit immediately after surgery, or a patient’s neurological recovery potential at six months. The prognostic value of DWI change on OS in specific subgroups warrants further investigation.