Malignant supratentorial astrocytoma treated with postoperative radiation therapy: prognostic value of pretreatment quantitative diffusion-weighted MR imaging.

PURPOSE: To retrospectively evaluate whether the minimum apparent diffusion coefficient (ADC) of the tumor seen on pretreatment magnetic resonance (MR) images is of prognostic value in patients with malignant supratentorial astrocytoma.

MATERIALS AND METHODS: The study was approved by the institutional review board; the requirement for informed patient consent was waived. Between June 1996 and November 2003, 79 patients (44 male, 35 female; age range, 16-76 years) with malignant supratentorial astrocytoma underwent pretreatment MR imaging. Patient age, symptom duration, neurologic function, mental status, Karnofsky performance scale (KPS) score, extent of surgery, histopathologic diagnosis, tumor component enhancement, and minimum ADC were assessed at factor analysis of survival. Radiation Therapy Oncology Group-recursive partitioning analysis (RTOG-RPA) criteria were used to validate the prognostic value of the minimum ADC. Kaplan-Meier survival curves, the log-rank test, and the multivariate Cox proportional hazards model were used to evaluate the prognostic factors.

RESULTS: Twenty-nine patients had anaplastic astrocytoma, and 50 had glioblastoma multiforme. The minimum ADC was significantly lower in patients with glioblastoma multiforme than in those with anaplastic astrocytoma (P < .001). The two-year survival rates associated with low (1.0 x 10(-3) mm(2)/sec) minimum ADCs were 14% (six of 42 patients) and 84% (31 of 37 patients), respectively (P < .001). The minimum ADC was the most important prognostic factor (hazard ratio = 10.459; 95% confidence interval: 5.113, 21.396) and could be used to assign patients to different prognostic groups in each RTOG-RPA class.

CONCLUSION: The minimum ADC at pretreatment MR imaging is a useful clinical prognostic biomarker for survival in patients with malignant supratentorial astrocytoma.