NIMG-22. MRI CHANGES IN NEWLY DIAGNOSED GLIOBLASTOMA DURING CHEMORADIATION AND ADJUVANT TEMOZOLOMIDE

Abstract

Characterize anatomic and functional MRI changes in patients with newly diagnosed glioblastoma (nGBM) to more accurately measure impact of treatment. The standard of care for nGBM is maximal safe resection, six weeks of concurrent chemoradiation (CRT), followed by adjuvant monthly temozolomide. FLAIR and T1 post-contrast sequences are frequently used to assess treatment response but poorly reflect underlying tumor behavior with respect to tumor cellularity, vascular permeability, and perfusion. Following IRB approval, patients with nGBM underwent MR imaging before treatment, during week 6 of CRT, four weeks post-CRT, and before cycle 2 of adjuvant temozolomide (“pre-cycle 2”). We measured FLAIR and contrast-enhancing (CE) volumes, apparent diffusion coefficient (ADC; reflecting tumor cellularity), Ktrans (reflecting vascular permeability), and relative cerebral blood volume (rCBV) and flow (rCBF; reflecting perfusion) on spin echo (SE) and gradient echo (GE) sequences (rCBVSE, rCBFSE, rCBVGE, rCBFGE, respectively). Fourteen patients were included. Percent changes during treatment were compared to pre-treatment values. Within the CE region of interest (ROI), the respective median percent changes during CRT, post-CRT, and pre-cycle 2 were: CE volume -0.75%, 19.98%, 5.93%; ADC 10.15%, 18.03%, 27.21%; Ktrans 32.05%, 22.48%, 7.06%; rCBVSE -18.82%, -33.21%, -32.86%; rCBFSE -11.42%, -28.80%, -26.99%; rCBVGE -17.05%, -23.92%, -30.39%; and rCBFGE -21.98%, -24.29%, -32.12%. Within the peri-tumoral FLAIR ROI, the respective median percent changes during CRT, post-CRT, and pre-cycle 2 were: FLAIR volume 20.36%, 80.29%, 69.36%; ADC -3.63%, 6.59%, 11.51%; Ktrans 5.88%, -7.40%, -31.45%; rCBVSE -11.62%, -34.60%, -20.18%; rCBFSE -0.31%, -22.42%, -25.23%; rCBVGE -0.80%, -13.05%, -22.32%; and rCBFGE 6.30%, -6.25%, -19.57%. Chemoradiation in nGBM results in increased edema and permeability early during treatment, likely related to tumoral and peri-tumoral inflammation; decreased tumor cellularity, reflected by increased ADC; and decreased perfusion. ADC, Ktrans, and perfusion parameters are thus helpful in better characterizing tumor microenvironment during treatment.