Natural history and spontaneous prognostic factors

Abstract

Low-grade gliomas (LGGs) are a group of tumors with distinct clinical, histological, and molecular characteristics. The most common presenting symptom is represented by seizures that in MRI era occur in 70-90 % of patients with low-grade gliomas and are medically refractory in about 50 % of cases. LGGs typically affect young adults and are rare in elderly patients (>60 years). Occasionally, grade II glioma is discovered incidentally on brain imaging. The natural history and patterns of care of LGGs have changed over time with an increase of survival, which is, at least in part, due to the earlier diagnosis afforded by CT and MRI. Overall the 5-year survival rates reported in recent randomized trials are in the order of 64-68 %. A number of retrospective and a few prospective series have evaluated variables of potential prognostic significance in patients with LGG. Some of these factors have been fully validated: age >40 years, presence of neurological deficits and/or absence of seizures at onset, low performance status (Karnofsky < 70), preoperative tumor diameter > 4-6 cm, astrocytoma as histology, while others still need validation (Table 18.1). Among molecular markers, 1p-19q codeletion and IDH1 mutation are the most important prognostic factors. Based on the prognostic factors that emerged as significant after multivariate analysis among large, randomized multicenter trials, several prognostic scoring systems have been developed to identify subgroups of patients with different outcome (so-called low- and high-risk groups).