The Prognostic Role of Volumetric MRI Evaluation in the Surgical Treatment of Glioblastoma

Abstract

Background: Glioblastoma is the most common primary brain neoplasm in adults, with a poor prognosis despite a constant effort to improve patient survival. Some neuroradiological volumetric parameters seem to play a predictive role in overall survival (OS) and progression-free survival (PFS). The aim of this study was to analyze the impact of the volumetric areas of contrast-enhancing tumors and perineoplastic edema on the survival of patients treated for glioblastoma. Methods: A series of 87 patients who underwent surgery was retrospectively analyzed; OS and PFS were considered the end points of the study. For each patient, a multidisciplinary revision was conducted in collaboration with the Neuroradiology and Neuro-Oncology Board. Manual and semiautomatic measurements were adopted to perform the radiological evaluation, and the following quantitative parameters were retrospectively analyzed: contrast enhancement preoperative tumor volume (CE-PTV), contrast enhancement postoperative tumor volume (CE-RTV), edema/infiltration preoperative volume (T2/FLAIR-PV), edema/infiltration postoperative volume (T2/FLAIR-RV), necrosis volume inside the tumor (NV), and total tumor volume including necrosis (TV). Results: The median OS value was 9 months, and the median PFS value was 4 months; the mean values were 12.3 and 6.9 months, respectively. Multivariate analysis showed that the OS-related factors were adjuvant chemoradiotherapy (p < 0.0001), CE-PTV < 15 cm³ (p = 0.03), surgical resection > 95% (p = 0.004), and the presence of a "pseudocapsulated" radiological morphology (p = 0.04). Conclusions: Maximal safe resection is one of the most relevant predictive factors for patient survival. Semiautomatic preoperative MRI evaluation could play a key role in prognostically categorizing these tumors.

Keywords: FLAIR infiltration; brain tumors; extent of surgical resection; glioblastoma; neuro-oncology; overall survival; progression-free survival; pseudocapsule; tumor volume.

Figure 1

CE-PTV, contrast-enhanced T1 weighted (CE-T1w) images by contouring manually enhanced tumor areas on every single axial slice, excluding necrosis.

Figure 2

CE-PTV, contrast-enhanced T1 weighted (CE-T1w) images performed with the semiautomatic method using the specific tool of the AW Server 3.2. The yellow box represents the area selected by the radiologist that the software analyzes (semi-automatic method).

Figure 3

Contrast enhancement postoperative tumor volume (CE-RTV) manual evaluation, achieved with subtraction imaging technique to minimize errors due to the spontaneous hyperintensity of degradation products of hemoglobin.

Figure 4

Contrast enhancement postoperative tumor volume (CE-RTV) semiautomatic evaluation, assessed on 2D axial CE-T1w images (slice thickness: 5 mm; slice spacing: 5.5–6 mm), achieved with the semiautomatic subtraction imaging technique.

Figure 5

Edema/infiltration preoperative volume (T2/FLAIR-PV), evaluated manually on axial hybrid sequences resulting from FLAIR (slice thickness: 5 mm; slice spacing: 5.5 mm) and CE-T1w in order to exclusively measure the edema/infiltration component, excluding the tumor (enhancing mass) previously assessed with CE-PTV and CE-RTV measurements.

Figure 6

Edema/infiltration postoperative volume (T2/FLAIR-RV), evaluated manually on axial hybrid sequences resulting from FLAIR and CE-T1w fusion in order to exclusively measure the edema/infiltration component, excluding the tumor (enhancing mass).

Figure 7

Necrosis volume inside the tumor, evaluated manually on preoperative 2D axial CE-T1w images, including only the necrotic area inside the tumor.

Figure 8

Thin, with enhancing wall thickness < 3 mm (left); thin-nodular, with enhancing wall focal thickenings > 3 mm (center); and nodular, with solid appearance predominant and intratumoral necrosis absent or less than 1.5 cm³ (right).