Evidence-based Guidelines for Low Grade Gliomas
Rock, J. J Neurooncol (2015) 125: 447. doi:10.1007/s11060-015-1824-z
Of 2624 citations, 59 were reviewed and determined to be sufficiently rigorous in design and methodology to be categorized and serve as the basis for the final management recommendations. The only management recommendation supported by high quality Class I evidence was to obtain a pathological diagnosis when a decision to treat a patient with a presumed low grade glioma was made, because there was no other way to be certain of the diagnosis despite the availability of sophisticated MRI imaging. All other clinical recommendations including whether or not to observe patients without intervention, whether or not to attempt radical removal of tumor, or whether or not to recommend post-operative radiation were supported by only Class III evidence and, therefore, were considered as treatment options.
Since this original guidelines effort, many publications from highly respected and experienced groups have appeared in the literature. Significant developments in radiological imaging have allowed us to evaluate not only the overall metabolic activity of brain tumors but also the metabolic heterogeneity within a given tumor. Other radiological developments now allow us to image critical neurologic pathways as they extend from the cerebral cortex to the spinal cord. We can now image intra-operatively the relationships between these pathways and the tumor itself, thereby providing an opportunity to remove the tumors with predictably lower patient morbidities. Additionally, intra-operative cortical mapping, now commonplace, gives surgeons the best chance to identify eloquent cortex surrounding tumors and thereby avoid additional patient morbidity. Intra-operative MRI and other techniques give us the ability to be more certain that the tumor has truly been removed to the greatest extent possible. Although extent of resection has repeatedly been noted to be a strong and independent factor associated with improved survival, it remains unsupported by high quality evidence. Radiation therapy remains an accepted post-operative management strategy for many patients and advances in our understanding of radiation and tumor biology, coupled with our ability to deliver focused high dose radiation, have possibly improved patient outcomes. Adjuvant chemotherapy, although not considered a treatment option for these patients in 1994, has become a treatment option. New research frontiers are exploring the possibility of capitalizing on the knowledge obtained on the molecular basis of LGG, to develop individualized treatments.
It will be the responsibility for all members of brain tumor patient care teams to carefully assess and report clinical results from properly conducted studies in the contemporary literature as time passes. Only in this way will the path to truly excellent clinical understanding and patient outcomes become clear.