EPIDERMAL GROWTH-FACTOR RECEPTOR AND LABELING INDEX ARE INDEPENDENT PROGNOSTIC FACTORS IN GLIAL TUMOR OUTCOME

The aim of this study was to perform a multivariate analysis including clinical and biological prognostic factors on glial tumor outcome. Se venty-nine patients were analyzed (48 men and 31 women; mean age = 56 years, range 16-77 years): 7 had a benign glial tumor (grades 1 and 2) , 21 had an anaplastic glial tumor (grade 3), and 51 had a glioblastom a (grade 4), Median follow-up was 17.9 months for patients who survive d (50 patients died). Biopsies were obtained at time of diagnosis (com plete tumor resection in 62 patients and stereotaxic biopsies in 17 pa tients). Epidermal growth factor receptor (EGFR) was measured by a bin ding assay, and labeling index (LI) was measured by tritiated thymidin e incorporation. EGFR varied from 4 to 73,110 fmol/mg protein (mean = 3912 fmol/mg protein; median = 374 fmol/mg protein; n = 79), LI varied between 0.1 and 16.5% (mean 6.2%; median = 5.2%; n = 40), Log(10) EGF R was significantly and positively correlated with patient age. LI was significantly different according to tumor histology. Univariate Cox analysis (end point was cancer death) showed that age (P = 0,027), log (10) EGFR (P = 0.025), and LI (P = 0.0019) were significant continuous variables, the survival being shortened when the covariable increased ; tumor resection (P = 0.015, relative risk = 0.45) and histology (P = 0.0009) were significant categorical factors. A multivariate Cox anal ysis (forward selection) including age, histology, tumor resection, lo g(10) EGFR, and LI revealed that log(10) EGFR, LI, and tumor resection were the only independent significant predictors of survival. This mu ltivariate approach reveals that the clinical prognostic factors of gl ial tumors, namely age and tumor histology, disappear, to the benefit of intrinsic characteristics of the tumor, log(10) EGFR expression and LI, suggesting that coupled EGFR and LI determination could be a usef ul tool for better evaluation of glial tumor outcome.