Therapeutic Decision Making in Patients with Newly Diagnosed Low Grade Glioma

Low grade gliomas (LGG) encompass primary brain tumors that are typically well-differentiated and do not exhibit frankly malignant histologic features. These tumors can be further classified by their cellular morphology (eg, oligodendroglioma, pilocytic astrocytoma, etc), which does convey prognostic and therapeutic implications. Typically, low grade gliomas convey an overall better prognosis for patients as opposed to the higher grade primary brain tumors. Surgery for low grade gliomas and timing of such intervention remains controversial. Maximal resection of these tumors appears to prolong progression free survival. Advanced surgical techniques, including language mapping and awake craniotomies, have been shown to decrease morbidity associated with resection of lesions in eloquent areas of the brain. Radiation therapy has been proven effective in increasing time to progression in LGG, and emerging data support a role for combined modality therapy incorporating chemotherapy. Postoperative RT has been shown to have significant benefits with regards to progression free survival. Recent advances in molecular genetic markers, including the combined loss of chromosome arms 1p and 19q, and the mutation of the isocitrate dehydrogenase gene (IDH1/IDH2) have allowed for increased accuracy of predicting susceptibility to chemotherapeutic agents, as well as having some role in determining prognosis. PCV and temozolomide chemotherapy have both been studied when assessing progression free survival for LGG patients. Approaching patients with LGGs can be somewhat daunting given the lack of Class I evidence based protocols. However, significant evidence is now mounting to suggest early, maximal surgical excision; followed by fractionated RT will be the mainstays of treatment. Clearly, additional evidence is also mounting for the addition of chemotherapy in the treatment paradigm for patients with LGGs.