Volumetric quantification of glioblastoma: experiences with different measurement techniques and impact on survival

The potential impact of different radiological features of glioblastoma multiforme (GBM) on overall survival (OS) like tumor volume, peritumoral edema (PTE), necrosis volume, necrosis-tumor ratio (NTR) and edema-tumor ratio (ETR) is still very controversial. To determine the influence of volumetric data on OS und to compare different measuring techniques described in literature. We prospectively evaluated preoperative MR images from 30 patients harboring a primary supratentorial GBM. All patients received gross-total tumor resection followed by standard radiation and chemotherapy (temozolomide). By 3D semi-automated segmentation, we measured tumor volume, necrosis volume, PTE, postoperative residual tumor volume and calculated ETR, NTR and the extent of resection. After critical review of the existing literature we compared alternative measuring techniques with the gold standard of 3D segmentation. Statistical analysis showed a significant impact of the preoperative tumor and necrosis volumes on OS (p = 0.041, respectively p = 0.039). Furthermore, NTR also showed a significant association with OS (p = 0.005). Comparison of previously described measuring techniques and scorings with our results showed that no other technique is reliable and accurate enough as a predictive tool. The critical review of previously published studies revealed mainly inaccurate measurement techniques and patient selection as potential reasons for inconsistent results. Preoperatively measured necrosis volume and NTR are the most important radiological features of GBM with a strong influence on OS. No other measuring techniques are specific enough and comparable with 3D segmentation.