Can MRI-derived factors predict the survival in glioblastoma patients treated with postoperative chemoradiation therapy?

BACKGROUND Advanced diagnostic and therapeutic developments may yield novel prognostic factors in patients with glioblastoma multiforme (GBM). PURPOSE To validate the predictive values of pretreatment quantitative diffusion-weighted (DW) magnetic resonance imaging (MRI) and MRI performed within 72 h after surgery in patients with GBM. MATERIAL AND METHODS Between January 2000 and September 2009, 138 patients with GBM underwent postoperative chemoradiation therapy (chemo-RT) and longitudinal MRI before surgery, in the early postoperative period, and at 1-month intervals thereafter. The role of the patient age, Karnofsky performance scale (KPS) score, minimum apparent diffusion coefficient (ADC) on pretreatment DW-MRI, and gross residual tumor on early postoperative MRI were assessed by factor analysis of overall survival (OS). Survival curves were calculated using the Kaplan-Meier method; the multivariate Cox's proportional hazards model was used to adjust for the influence of prognostic factors. Radiation Therapy Oncology Group-recursive partitioning analysis (RTOG-RPA) criteria were used to validate the predictive value of the MRI-derived factors. RESULTS Substantial independent prognostic factors were the KPS score (hazard ratio [HR], 1.812), minimum ADC (HR, 2.365), and gross residual tumor (HR, 1.777). Based on MRI-derived factors, we assigned the patients to different prognostic groups in the RTOG-RPA classification and grouped them according to the level of risk, i.e. a high-risk group with low minimum ADCs (<0.93 × 10(-3) mm(2)/s) with gross residual tumor and a low-risk group with high minimum ADCs (≥0.93 × 10(-3) mm(2)/s) without gross residual tumor; the other patients were assigned to the intermediate-risk group. Median OS for the low-, intermediate-, and high-risk groups were 28.2, 14.7, and 10.8 months, respectively (P < 0.001). CONCLUSION The minimum ADC on pretreatment DW-MRI and gross residual tumor on early postoperative MRI can predict the survival in GBM patients treated with postoperative chemo-RT.