Glioblastoma survival is better analyzed on preradiotherapy MRI than on postoperative MRI residual volumes: A retrospective observational study.

Objectives: Establishing an overall survival prognosis for resected glioblastoma during routine postoperative management remains a challenge. The aim of our single-center study was to assess the usefulness of basing survival analyses on preradiotherapy MRI (PRMR) rather than on postoperative MRI (POMR).
Patients and Methods: A retrospective review was undertaken of 75 patients with glioblastoma treated at our institute. We collected overall survival and MRI volumetric data. We analyzed two types of volumetric data: residual tumor volume and extent of resection. Overall survival rates were compared according to these two types of volumetric data, calculated on either POMR or PRMR and according to the presence or absence of residual enhancement.
Results: Analysis of volumetric data revealed progression of some residual tumors between POMR and PRMR. Kaplan-Meier analysis of the correlations between extent of resection, residual tumor volume, and overall survival revealed significant differences between POMR and PRMR data. Both MRI scans indicated a difference between the complete resection subgroup and the incomplete resection subgroup, as median overall survival was longer in patients with complete resection. However, differences were significant for PRMR (25.3 vs. 15.5, p =  0.012), but not for POMR (21.3 vs. 15.8 months, p =  0.145). With a residual tumor volume cut-off value of 3 cm ³ , Kaplan-Meier survival analysis revealed non-significant differences on POMR (p =  0.323) compared with PRMR (p =  0.007).
Conclusion: Survival in patients with resected glioblastoma was more accurately predicted by volumetric data acquired with PRMR. Differences in predicted survival between the POMR and PRMR groups can be attributed to changes in tumor behavior before adjuvant therapy.
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