Glioblastoma has an unfavorable prognosis mainly due to its high propensity for tumor recurrence. It has been suggested that GBM recurrence is inevitable after a median survival time of 32 to 36 weeks 1) 2).
The natural history of recurrent GBM, is largely undefined for the following reasons:
1) Lack of uniform definition and criteria for tumor recurrence
2) Institutional variability in treatment philosophy
3) The heterogeneous nature of the disease, including location of recurrence and distinct mechanisms believed to contribute to known subtypes of GBM.
The criteria used to define recurrent glioblastoma GBM remain ambiguous due to the varied presentation of new lesions. First, the infiltrative nature of GBM cells makes it difficult to eliminate microscopic disease despite macroscopic gross-total resection. Studies have shown that GBM recurrence most often occurs in the form of a local continuous growth within 2 to 3 cm from the border of the original lesion 3) 4) 5).
One of the factors that cause recurrence is the strong migratory capacity of GBM cells. Wanibuchi et al., reported that actin, alpha, cardiac muscle 1 (ACTC1) could serve as a marker to detect GBM migration in clinical cases 6).
Glioblastoma demonstrates considerable intratumoral phenotypic and molecular heterogeneity and contains a population of cancer stem cells (CSC) that contributes to tumor propagation, maintenance, and treatment resistance.
These cells are associated with vascular niches which regulate glioma stem cells (GSC) self-renewal and survival.
Studies suggest that while blood vessels support glioma stem cells, these tumor cells in turn may regulate and contribute to the tumor vasculature by transdifferentiating into endothelial cells directly or through the secretion of regulatory growth factors such as vascular endothelial growth factor (VEGF) and hepatoma derived growth factor (HDGF) 7).
Corns et al. describe the case of a patient with recurrent glioblastoma encroaching on Broca's area. Gross total resection of the tumour was achieved by combining two techniques, awake craniotomy to prevent damage to eloquent brain and 5 aminolevulinic acid fluorescence guided resection to maximise the extent of tumour resection. This technique led to gross total resection of all T1-contrast enhancement tumour with the avoidance of neurological deficit. They recommend this technique in patients when awake surgery can be tolerated and gross total resection is the aim of surgery 10).