EGFR overexpression and radiation response in glioblastoma multiforme

Purpose: Recent studies have suggested relative radioresistance in glioblas toma multiforme (GM) tumors in older patients, consistent with their shorte r survival. Two common molecular genetic abnormalities in GM are age relate d: epidermal growth factor receptor (EGFR) overexpression in older patients and p53 mutations in younger patients. We tested whether these abnormaliti es correlated with clinical heterogeneity in GM response to radiation treat ment. Methods and Materials: Radiographically assessed radiation response (5-leve l scale) was correlated with EGFR immunoreactivity, p53-immunoreactivity, a nd p53 exon 5-8 mutation status in 170 GM patients treated using 2 prospect ive clinical protocols. Spearman rank correlation and proportional-odds ord inal regression were used for univariate and multivariate analysis. Results: Positive EGFR immunoreactivity predicted poor radiographically ass essed radiation response (p = 0.46). Thirty-three percent of tumors with no EGFR immunoreactivity had good radiation responses (> 50% reduction in tum or size by CT or MRI), compared to 18% of tumors with intermediate EGFR sta ining and 9% of tumors with strong staining. There was no significant relat ionship between p53 immunoreactivity or mutation status and radiation respo nse. Significant relationships were noted between EGFR score and older age and between p53 score or mutation status and younger age. Conclusion: The observed relative radioresistance of some GMs is associated with overexpression of EGFR. (C) 2001 Elsevier Science Inc.