The role of surgery in the management of patients with diffuse low grade glioma: A systematic review and evidence-based clinical practice guideline.

QUESTION: Should patients with imaging suggestive of low grade glioma (LGG) undergo observation versus treatment involving a surgical procedure? TARGET POPULATION: These recommendations apply to adults with imaging suggestive of a WHO grade 2 glioma (oligodendroglioma, astrocytoma, or oligo-astrocytoma). RECOMMENDATIONS: Surgical resection is recommended over observation to improve overall survival for patients with diffuse low-grade glioma (Level III) although observation has no negative impact on cognitive performance and quality of life (Level II). QUESTION: What is the impact of extent of resection on progression free survival (PFS) or overall survival (OS) in LGG patients? TARGET POPULATION: These recommendations apply to adults with imaging suggestive of a WHO grade 2 glioma (oligodendroglioma, astrocytoma, or oligo-astrocytoma). RECOMMENDATIONS: IMPACT OF EXTENT OF RESECTION ON PFS: LEVEL II: It is recommended that GTR or STR be accomplished instead of biopsy alone when safe and feasible so as to decrease the frequency of tumor progression recognizing that the rate of progression after GTR is fairly high. LEVEL III: Greater extent of resection can improve OS in LGG patients. QUESTION: What tools are available to increase extent of resection in LGG patients? TARGET POPULATION: These recommendations apply to adults with imaging suggestive of a WHO grade 2 glioma (oligodendroglioma, astrocytoma, or oligo-astrocytoma). RECOMMENDATIONS: INTRAOPERATIVE MRI DURING SURGERY: LEVEL III: The use of intraoperative MRI should be considered as a method of increasing the extent of resection of LGGs. QUESTION: What is the impact of surgical resection on seizure control and accuracy of pathology in low grade glioma patients? TARGET POPULATION: These recommendations apply to adults with imaging suggestive of a WHO grade 2 glioma (oligodendroglioma, astrocytoma, or oligo-astrocytoma). RECOMMENDATIONS: SURGICAL RESECTION AND SEIZURE CONTROL: LEVEL III: After taking into account the patient's clinical status and tumor location, gross total resection is recommended for patients with diffuse LGG as a way to achieve more favorable seizure control. LEVEL III: Taking into account the patient's clinical status and tumor location, surgical resection should be carried out to maximize the chance of accurate diagnosis. QUESTION: What tools can improve the safety of surgery for LGGs in eloquent locations? TARGET POPULATION: These recommendations apply to adults with imaging suggestive of a WHO grade 2 glioma (oligodendroglioma, astrocytoma, or oligo-astrocytoma). RECOMMENDATIONS: PREOPERATIVE IMAGING: LEVEL III: It is recommended that preoperative functional MRI and diffusion tensor imaging be utilized in the appropriate clinical setting to improve functional outcome after surgery for LGG. LEVEL III: Intraoperative mapping is recommended for patients with diffuse LGGs in eloquent locations compared to patients with non-eloquently located diffuse LGGs as a way of preserving function.