Assess incidence and degree of tumor recurrence in patients s/p surgical resection of GBM relative to time between surgery and RT.
Materials/Methods
Thirty-two patients with newly diagnosed GBM accrued through a SPORE protocol that subjected them to advanced MR imaging-MRI, 3D MR Spectroscopy (MRSI), perfusion (PWI), diffusion weighted imaging (DWI)-at multiple points including immediately post-surgery and prior to initiation of adjuvant treatment (3D-CRT and Temodar-based chemotherapy). Regions of contrast enhancement (CE) on pre-RT MRI were outlined and compared visually to extent of reduced diffusion seen on postsurgical DWI to differentiate tumor growth/recurrence from postsurgical injury. MR parameters were calculated for regions of CE including: from MRSI, peak heights for Choline, Creatine, NAA, Lactate, Lipid; from PWI, peak height (PH) and percent recovery (Rec); from DWI, apparent diffusion coefficient (ADC) and fractional anisotropy (FA). Statistical analyses included rank sum tests.
Results
Eighteen patients were considered gross total resections while 14 patients were subtotal resections. RT was initiated 14 to 46 days after surgery (median 32.5) with pre-RT imaging acquired 5–21 days prior to RT (6 median). Regions of reduced diffusion were seen in 21 patients post surgery; 25 patients showed new/increased CE pre-RT. In 8 patients new CE was spatially confined/related only to areas of postsurgical reduced diffusion. In 17 patients at least some portion of new CE was spatially unrelated to postsurgical diffusion abnormalities and was considered indicative of tumor growth (6) or a combination of tumor growth and surgical injury (11). Metabolic and physiologic imaging parameters demonstrated higher Cho, Cho-to-NAA and Cho-to-Cr indices with a trend toward reduced ADC suggesting active metabolism and tumor cell proliferation in patients with presumed tumor growth vs. patients with postsurgical injury. Survival was significantly worse in patients with interim tumor recurrence (median 15.1 months) vs. those without recurrence (median 22.2 months) (p = 0.015).
Conclusions
Tumor recurrence occurs in a considerable portion of patients (53%) during the interval between surgery and RT with a negative impact on survival. These data support the value of pre-RT imaging in conjunction with metabolic/physiologic imaging at that time or with postsurgical DWI in order to refine interpretation of contrast enhancement and, ultimately, to improve patient selection and management as well as RT treatment planning. Finally, consideration should be given to an earlier start of RT.
Author Disclosure: A. Pirzkall, None; C. McGue, None; S. Saraswathy, None; S. Cha, None; R. Liu, None; M.S. Berger, None; S.M. Chang, None; S.J. Nelson, None.
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