Changes in tumor enhancement detected by post-gadolinium (Gd) T1-weighted MRI are highly predictive of which patients with recurrent glioblastoma brain tumors will benefit from second-line therapy, according to results of a study presented today at RSNA 2012.
Currently, using MRI to assess if a tumor is responding to treatment with bevacizumab is difficult because of the drug’s potential for decreasing tumor enhancement independent of decreasing tumor burden. Researchers undertook the study to see if disease progression as seen on MRI that used post-Gd 2D- or 3D-T1 or FLAIR sequences would reliably predict patient outcome.
“Our study results demonstrate that even though tumor enhancement may diminish with the use of bevacizumab, a finding of progressive enhancement on the T1-weighted images highly correlates with worse patient outcome,” principal investigator Jerrold Boxerman, MD, PhD, said in a release issued by the American College of Radiology Imaging Network (ACRIN). Boxerman is an assistant professor at the Warren Alpert Medical School of Brown University in Providence, RI. “Knowing that a patient is not benefitting from a treatment could permit a timely switch to a clinical trial evaluating an alternate therapeutic strategy.”
The researchers collected clinical and imaging data as part of the Radiation Therapy Oncology Group (RTOG 0625) and ACRIN (ACRIN 6677) multi-center randomized phase II trial of bevacizumab with irinotecan or temozolomide for patients with recurrent glioblastoma. Two radiologists serially measured 2D and 3D enhancement on post-Gd T1-weighted images and 3D fluid-attenuated inversion-recovery (FLAIR) hyperintensity images on 123 cases. A third neuroradiologist adjudicated interpretational discrepancies.
The researchers found that the medial overall survival rate, measured in days, of patients whose tumor had progressed after two cycles (eight weeks) and four cycles (16 weeks) of treatment was significantly less than that for patients whose tumor did not progress on the 2D-T1 images (114 vs. 278 and 214 vs. 426, p<0.0001 for both) and the 3D-T1 images (117 vs. 306, p<0.0001 and 223 vs. 448, p=0.0003), but not on the FLAIR images (201 vs. 276,p=0.38 and 303 vs. 321, p=0.13).
“Given the wide-spread use of bevacizumab for treating recurrent GBM, establishing a highly-predictive marker of treatment response would be extremely valuable for patient care. These study results suggest that the standard imaging techniques employed in the joint RTOG-ACRIN trial can provide important clinical information,” said Daniel Barboriak, MD, professor of radiology at Duke University Medical Center, Durham, NC and chair of the ACRIN Head/Neck and Neuro Committee.