Lobar Distribution of Low Grade Oligodendroglioma: Distribution, Molecular Characteristics, and Survival Based upon Location

Abstract

Grade II oligodendrogliomas are rare and slow growing tumors, making long-term follow up difficult, but necessary for better understanding. In this retrospective study a review of all grade II oligodendrogliomas encountered in the last 20 years at one institution, was undertaken to determine if specific tumor location and immunohistochemical analysis had any impact on recurrence rate, progression free survival, or life expectancy. Eighty-nine grade II oligodendroglioms cases were reviewed (38 females and 51 males; mean age was 40.3 ± 13.8 years). Tumor location was: frontal lobe (44, 49.4%) and superior frontal gyrus (30, 33.7%). 1p19q data were available in 49 patients. Twenty-nine cases were co-deleted (59.2%). There was no significant difference in the incidence of 1p19q co-deletion between superior frontal gyrus tumors vs. other frontal tumors or extra-frontal tumors ( p = 0.45). Follow up of at least 3 months after diagnosis was available in 79 patients (mean follow up: 93.2 months). In recurrence analysis, recurrence by 1p19q status and recurrence by location revealed no significant differences. In analysis of progression, progression by 1p19q status and progression by location revealed no significant differences. An analysis of deaths for the sample, deaths by 1p19q status and deaths by location revealed no significant differences. There was a higher death rate among patients >50 years of age, however this, too, was not significant. There did not appear to be any advantage in recurrence rate, progression free survival, or life expectancy for tumors located in the frontal lobe or superior frontal gyrus. 1p19q co-deletion did not appear to confer an advantage as measured by time to recurrence, time to progression, or overall survival. Other than age, eloquent location, Karnofsky status, and overall tumor size as reported by others, tumor location and 1p19q status in low grade oligodendrogliomas are not currently predictive of survival.