Age and radiation response in glioblastoma multiforme

OBJECTIVE: Advanced age is a strong predictor of shorter survival in patien ts with glioblastoma multiforme (GM), especially for those who receive mult imodality treatment. Radiographically assessed tumor response to external b eam radiation therapy is an important prognostic factor in GM. We hypothesi zed that older GM patients might have more radioresistant tumors. METHODS: We studied radiographically assessed response to external beam rad iation treatment (five-level scale) in relation to age and other prognostic factors in a cohort of 301 GM patients treated on two prospective clinical protocols. A total of 223 patients (74%) were assessable for radiographica lly assessed radiation response. A proportional odds ordinal regression mod el was used for univariate and multivariate analysis. RESULTS: Younger age (P = 0.006), higher Karnofsky Performance Scale score before radiotherapy (P = 0.027), and more extensive surgical resection (P = 0.028) predicted better radiation response in univariate analyses. Results were similar when clinical criteria were used to classify an additional 61 patients without radiographically assessed radiation response (stable vers us progressive disease). In multivariate analyses, age and extent of resect ion were significant independent predictors of radiation response (P < 0.05 ); Karnofsky Performance Scale score was of borderline significance (P = 0. 07). CONCLUSION: Older GM patients are less likely to have good responses to pos toperative external beam radiation therapy. Karnofsky Performance Scale sco re before radiation treatment and extent of surgical resection are addition al predictors of radiographically assessed radiation response in GM.