[WHO grade II gliomas: review of the current management]

The optimal management of diffuse WHO grade II gliomas (GGII) is still controversial. Some authors propose a long-term radiological follow-up of the tumor, others perform a biopsy and treat only if clinical or radiological signs of progression, finally, others propose an active treatment from diagnosis. There is mounting evidence that suggest that expectant management is no longer optimal, supporting active treatment from diagnosis. In the present work, an extensive review of the recent literature was performed, in order to clarify some of these controversies. Neuroimaging techniques, such as magnetic resonance imaging (MRI), multivoxel spectroscopy or methionine positron emission tomography (PET), give valuable information about the tumor, but lack of sufficient reliability to make a definitive diagnosis of GGII. Stereotactic biopsy leads to misdiagnosis in up to 71% of cases, which has been associated with sampling errors and inter-observer variability due to the small sample obtained. Therefore, it is now considered that a definitive diagnosis of GGII requires a detailed histological analysis of the sample after maximum tumor removal. Despite the lack of class I evidence, there is growing evidence from cohort studies, favoring extensive surgical resection to improve survival and time to tumor degeneration. Surgery is also effective to treat epilepsy, as an improvement in up to 76% of drug-resistant epilepsies has been documented. Consequently, surgery is now considered as a crucial step for diagnosis and treatment of these tumors. Early radiotherapy after surgery lengthens the period without progression but does not affect overall survival, and is related to cognitive disorders that affect quality of life. Hence, this treatment could be deferred until tumor progression.