Surgery for diffuse low-grade gliomas (DLGG) oncological considerations

Abstract

For a long time, surgery for DLGG was a matter of debate. The main problem explaining discrepancies in the classical literature is related to the fact that, in the vast majority of series, extent of resection (EOR) was not objectively assessed on postoperative MRI. It was based on the sole subjectivity of the surgeons or on a single computed tomography scan, with no volume measurement of the residue. In the modern series which used a systematic postoperative T2-/FLAIR-weighted MRI, all authors have demonstrated that a more aggressive resection predicted significant improvement in overall survival (OS) compared with a simple debulking. In addition, it was shown that an extended removal of a margin beyond these MR imaging-defined abnormalities, that is, a supra-total resection, significantly increased OS by delaying malignant transformation. This means that biopsy in DLGG should be considered only in very diffuse lesions, such as gliomatosis, or when a subtotal resection is not a priori possible. Collectively, despite the lack of phase III study, these data strongly argue in favor of achieving a maximal resection of DLGG as the first therapeutic option. Thus, surgeons should change their mind in order to operate the brain involved by a chronic tumoral disease - and no more by operating a tumor mass within the brain. The goal is not to content with a single tumorectomy (i.e., to remove only the top of the iceberg visible on imaging) but to perform the most extensive resection of the brain invaded by DLGG on the condition that this part of the brain is not crucial for cerebral functions. In other words, neurosurgeons should take the habit to perform early and maximal resection according to functional (and not purely oncological or anatomical) boundaries in awake patients. This perspective seems to represent the best way to build a modern and personalized functional surgical neurooncology.