Many studies have reported that the extent of resection is a crucial positive prognostic factor in patients with GBM [7–10] The extent of the resection results is positively correlated with the progression-free and overall survival. However, there can be tumor recurrence even after GTR and standard chemo-radiotherapy. The extent of resection is defined based on postoperative T1-weighted contrast-enhanced MRI results. Nevertheless, there can be infiltration of GBM tumor cells well beyond contrast-enhancing areas. [11, 12] Even when postoperative MRI images show removal of enhancing lesions, there can be tumor recurrence due to infiltrating tumor cells. Most recurrent tumors occur adjacent to the resection margin or within 2 cm.[4, 13, 14]
This problem can be solved with the use of 5-ALA, which allows broader tumor resection since it reveals infiltrating tumor cells beyond the enhancing region. Although GTR was performed based on postoperative MRI, patients with residual 5-ALA fluorescent tumors at the surgical field showed worse outcomes than those without residual fluorescence. However, in this study with a small sample size, the use of 5-ALA did not significantly affect outcomes.
Given the recent emergence of SupTR, the exact interpretation of SupTR remains unclear.[17–19] Duffau used this term to describe extended resection with a margin beyond the MRI-defined abnormalities in low-grade gliomas . Therefore, we used T2 and FLAIR images as references for SupTR in low-grade gliomas. For GBMs, the term SupTR has been used to describe resection beyond the contrast-enhancing lesion.
This study considered lobectomy as part of the SupTR procedure. This procedure resulted in a significantly larger volume of the resection cavity compared with the initial tumor volume. Therefore, a larger resection cavity volume than the initial tumor volume can be considered as a criterion for SupTR.
In our study, the median PFS and median OS were 33.5 and 49.1 months, while the respective values in conventional GTR are 12 and 16 months. These findings indicated that SupTR procedures can provide clinical benefits for carefully selected patients with GBM showing non-eloquent tumor localization. This study proposes excision of the entire lobectomy as a paradigm for SupTR. Therefore, these findings are suggestive of lobectomy as an aggressive SupTR policy that constitutes the surgical modality of choice. However, lobectomy as an oncosurgical resection tool bears the risk of a postoperative decline in language, memory, and visual loss. However, given our retrospective design, a similar analysis was beyond the feasibility of our study. Subsequent prospective study designs might allow assessment of neurocognitive issues, and therefore provide a more comprehensive view of lobectomy as a potential seminal oncosurgical therapeutic strategy for GBM.
This study has several limitations. The main limitation was the acquisition of retrospectively collected data. Specifically, the patients were not randomized and treated according to the physician’s decision. However, to rule out the heterogeneity of non-eloquent tumor localization, we applied highly selective inclusion criteria for GBMs located in the frontal, temporal, and occipital lobes, which resulted in a small sample size. Additionally, the sample size was too small to reach a conclusion. There is a need for other large-scale studies. Finally, we only included data from a single center.