(ChemotherapyAdvisor)–Magnetic resonance imaging (MRI) is “highly” predictive of overall survival (OS) rates after bevacizumab-based VEGF blockade chemotherapy for glioblastoma multiforme, according to a multicenter, randomized Phase 2 trial presented at the Radiological Society of North America (RSNA)’s 2012 Scientific Assembly and Annual Meeting in Chicago, IL.

The study found that tumor progression assessed using 2-dimensional T1 magnetic resonance imaging (2D-T1 MRI) and 3D-T1 MRI – but not MRI fluid-attenuated inversion recovery (FLAIR) neuroimaging – is significantly associated with OS.

“Early post-therapy progressive 2-dimensional T1 and 3D-T1 enhancement may be a useful MRI biomarker for the failure of anti-VEGF therapy, permitting a timely switch to alternative trials when necessary,” reported lead author Jerrold Boxerman, MD, PhD, Assistant Professor of Diagnostic Imaging at the Warren Alpert Medical School of Brown University in Providence, RI, and coauthors.

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Pseudoresponses among patients receiving VEGF blockade “has raised concerns that radiologic response may not predict overall survival (OS),” the authors noted. Their analysis was undertaken to assess if patient OS is predicted by MRI-determined tumor progression after anti-VEGF chemotherapy.

Readers assessed MRI neuroimages for 107 patients (median age 56 years) enrolled in RTOG 0625/ACRIN 6677, a multi-center randomized Phase 2 study VEGF-blockade bevacizumab therapy plus irinotecan or temozolomide among patients with recurrent glioblastoma. Post-treatment MRI progression status was determined using Macdonald criteria, the authors reported.

Assessed MRI images were acquired using 2D-T1 MRI, 3D-T1, or FLAIR MRI.

Median OS among patients with MRI-determined tumor progression at 8 or 16 weeks was “significantly less than that for patients without progression on 2D-T1” (114 days vs. 278 days [P<0.0001] and 214 days vs. 426 days; P<0.0001, respectively) and for 3D-T1 (117 days vs. 306 days [P<0.0001] and 223 days vs. 448 days; P=0.0003), the authors reported.

FLAIR MRI images were not predictive of OS, however (201 days vs. 276 days at 8 weeks [P=0.38] and 303 days vs. 321 days at 16 weeks; P=0.13).

“Early progression on post-Gd 2D-T1 and 3D-T1, but not FLAIR MRI after 2 and 4 cycles (8 and 16 weeks) of anti-VEGF therapy has highly-significant prognostic value for OS,” the authors concluded.

The study was funded by the US National Cancer Institute (NCI U01-CA080098 and U01-CA079778).