Application of Delta T1 Maps for Quantitative and Objective Assessment of Extent of Resection and Survival Prediction in Glioblastoma

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BACKGROUND AND OBJECTIVES: Gross-total resection and low residual tumor volume (RTV) have been associated with increased survival in glioblastoma. Largely because of the subjectivity involved, the determination of gross-total resection and RTV remains difficult in the postoperative setting. In response, the objective of this study is to evaluate the clinical efficacy of an easy-to-use MRI metric, called delta T1 (dT1), to quantify the extent of resection (EOR) and RTV, in comparison with radiologist impression, to predict overall survival (OS) in patients with glioblastoma. METHODS: Fifty-nine patients who underwent resection of glioblastoma were retrospectively identified. dT1 images, automatically created from the difference between calibrated post- and precontrast T1-weighted images, were used to quantify EOR and RTV. Kaplan–Meier survival estimates were determined for EOR categories, an RTV cutoff of 5 cm3 and radiologist interpretation of EOR. Multivariate Cox proportional hazard regression analysis was used to evaluate RTV and EOR along with effects related to sex, Karnofsky Performance Scale, O[6]-methylaguanine-DNA methyltransferase (MGMT), and age on OS. RESULTS: Kaplan–Meier analysis revealed a statistically significant difference in median OS for a dT1-determined RTV cutoff of 5 cm3 (P = .0024, hazard ratio = 2.18 [1.232-3.856]), but not for radiological impression (P = .666) or dT1-determined EOR (P = .0803), which was limited to a comparison between partial and subtotal resections. Furthermore, when covariates were accounted for in multivariate Cox regression, significant differences in OS were retained for dT1-determined RTV. In addition, a significantly strong yet short-term effect of MGMT methylation status on OS was revealed for each RTV and EOR model. CONCLUSION: The utility of dT1 maps to quantify EOR and RTV in glioblastoma and predict survival suggests an emerging role for dT1s with relevance for intraoperative MRI, neuronavigation, and postoperative disease surveillance.