Long-term glioblastoma multiforme survivors: A population-based study

Abstract

Background: Long-term glioblastoma multiforme survivors (LTGBMS) are uncommon. The frequency which these occur in an unselected population and factors which produce these unusually long survivors are unknown. Objectives: To determine in a population-based study 1) the frequency of LTGBMS in a population and 2) identify which patient, treatment or tumor characteristics would predict which glioblastoma (GBM) patient would become a LTGBMS. Methods: The Alberta Cancer Registry was used to identify all patients diagnosed with GBM in southern Alberta between 1/1/75 - 12/31/91. Patient charts were reviewed and histology re-examined by a blinded neuropathologist. LTGBMS were defined as GBM patients surviving ≤ 3 years after diagnosis. Each LTGBMS was compared to three age-, gender-, and year of diagnosis- matched controls to compare patient, treatment, and tumor factors to GBM patients without long-term survival. Results: There were 279 GBMs diagnosed in the study period. Five (1.8%) survived ≤ three years (range, 3.2-15.8 years). Seven additional long-term survivors, who carded a diagnosis of GBM, were excluded after neuropathologic review; the most common revised diagnosis was malignant oligodendroglioma. LTGBMS (avg. age = 45 years) were significantly younger when compared to all GBM patients (avg. age = 59 years, p = 0.0001) diagnosed in the study period. LTGBMS had a higher KPS at diagnosis (p = 0.001) compared to controls. Tumors from LTGBMS tended to have fewer mitoses and a lower Ki-67 cellular proliferative index compared to controls. Radiation-induced dementia was common and disabling in LTGBMS. Conclusions: These data highlight the dismal prognosis for GBM patients who have both a short median survival and very small chance (1.8%) of long-term survival. The LTGBMS were younger, had a higher performance status, and their tumors tended to proliferate less rapidly than control GBM patients. When long-term survival does occur it is often accompanied by severe treatment- induced dementia.