Glioblastoma multiforme: relationship to subventricular zone and recurrence

Abstract

Neurogenesis in the adult mammalian brain is active in two areas: the subgranular zone in the dentate gyrus of the hippocampus and the subventricular zone. Cancer stem cells have been isolated from malignant brain tumors and it is widely believed they arise from transformed endogenous stem cells. We sought to determine if the initial location of glioblastoma (GB) as seen on conventional MRI and its relationship to the subventricular zone (SVZ) predicts the pattern of recurrence. We analyzed the initial (prior to any treatment) and last follow-up MR studies in 49 patients with GB. On post contrast images all non-treated GB were divided into three groups according to the relationship of their enhancing margins to the SVZ: Group I (directly in contact with the SVZ), Group II (in the subcortical [SC] region) and Group III (in both the SVZ and SC regions). Recurrences or continuous growth seen as enhancing areas on follow-up studies were characterized as local, spread, or distant according to their contact with the surgical bed and correlated with the locations of the initial tumors. Local and spread patterns of recurrence occurred with nearly equal frequency (45 and 43% each, respectively) and distant in 12%. In Group I, 80% showed a spread pattern, 20% a local pattern, and none a distant pattern. In Group II, 45% showed a spread pattern, 35% a local pattern, and a 20% distant one. In Group III, 58% showed a local pattern, 33% a spread pattern, and 8% distant one. Unlike other reports, the location of GB in relation to the SVZ in our patients did not predict the pattern of tumor recurrence and/or extension in our patients.

Keywords: cancer stem cells; glioblastoma; magnetic resonance imaging; recurrence; subventricular zone.

Figure 1

Schematic drawing of the 3 groups of glioblastoma (GB) according to the relationship of their enhancing margins to the SVZ. Group I, GB directly in contact with the SVZ. Group II, GB in contact to the subcortical (SC) region. Group III, GB contacting both the SVZ and SC regions.

Figure 2

Axial postcontrast T1-weighted images. A) Initially the study showed an enhancing GB, directly in contact with the left subventricular zone (Group I). B) The post-treatment image shows a ‘spread’ type of recurrence, which occurred within one centimeter of the original surgical bed. This was the most common pattern of recurrence observed in our study. Additionally note the tumor has now spread into the corpus callosum and that there is hydrocephalus.

Figure 3

A) Preoperative axial postcontrast T1-weighted image of an enhancing GB which is in contact with the subcortical fronto-parietal region (Group II). B) Post-treatment T1-weighted image of the same patient demonstrating a ‘distant’ type of recurrence located in the genu of corpus callosum and right frontal lobe that represents the least common type of recurrence found in our analysis

Figure 4

A) Axial postcontrast T1-weighted image of an enhacing GB prior to any treatment which is in contact with the subventricular zone of the right lateral ventricle atrium and also in contact to the temporal subcortical region (Group III). B). The post-treatment T1-weighted image illustrates the enhancing tumor within the original surgical bed thus being classified as a ‘local’ recurrence type. This was the most common recurrence type for this group.