Is the long-term survival of patients with intracranial glioblastoma multiforme overstated?

The 5-year survival rate for intracranial glioblastoma multiforme (GBM) has remained at 4-5% for the last 30 years, in spite of multiple randomized prospective trials. The authors hypothesized, based on the literature, that even this remarkably poor survival rate is an overstatement. They investigated this hypothesis using the the Duke University Medical Center Tumor Registry.

The authors reviewed all patients with the diagnosis of intracranial GBM recorded in the Duke University Medical Center Tumor Registry from the registry's inception in 1976 through 1996. This search identified a population of patients with a minimum of 5 years of follow-up. Each of the long-term survivors was assigned a code number for clinical information. The pathology slides were provided to a neuropathologist in a coded fashion so that the patients could not be identified. The neuropathologist reviewed the slides to analyze the presence or absence of nine histologic factors. A match technique was used to identify a control population of patients with GBM who were not 5-year survivors and were all deceased. The control population was compared with the study population to ascertain if there are histologic correlates associated with long-term survivorship.

The authors identified 766 patients recorded by the tumor registry as having an intracranial GBM with a minimum of 5 years of follow up. Of the total population, 32 patients initially appeared to be 5-year survivors (4%). Upon review of the medical records for these 32 patients, however, the authors found only 17 patients who were truly 5-year survivors. The most common reason for miscoding was the presence of a low-grade astrocytoma that subsequently dedifferentiated into GBM. The 17 long-term survivors included 11 males and 6 females. Their mean age at diagnosis was 40.2 years. Therapy consisted of a macroscopic total resection in 4 patients (22%), a biopsy in 1 patient (6%), a subtotal resection in 10 patients (56%), and unknown extent of resection in 2 patients (11%). All patients received partial brain irradiation (mean dose, 62.6 Gy) and chemotherapy. Thirteen different single-agent or combination chemotherapy programs were used. Two patients also received I-131 monoclonal antibody therapy. Analysis of the nine histopathologic factors studied showed that intermediate fibrillary elements were more common and small anaplastic elements were less common in the long-term survivors than in the control population.

Survival data on intracranial GBM, based on tumor registry data, should be interpreted cautiously. Reliable conclusions can only be drawn when such data are supplemented with clinical information and the histopathology is reviewed carefully. The group of long-term survivors in the current study were younger than the typical GBM population. Conventionally treated patients with GBM, chosen from an unselected population from a tumor registry, have a smaller chance of long-term survival than is generally believed.