Intraoperative MRI Facilitates Complete Glioma Resection

Daniel M. Keller, PhD

April 19, 2011

April 19, 2011 (Denver, Colorado) — The use of intraperative magnetic resonance imaging (iMRI) guidance in surgery to remove gliomas helps attain a higher rate of complete tumor resection than conventional microsurgery, a German research group reported here at the American Association of Neurological Surgeons 79th Annual Meeting.

This first randomized controlled trial of iMRI showed that such imaging results in lower residual tumor volumes than conventional microsurgery.

In a multivariate analysis, "the only factor that came out was the extent of resection being prognostic" for survival, according to lead author Christian Senft, MD, from the Department of Neurosurgery at Johann Wolfgang Goethe University in Frankfurt, Germany.

The study consisted of 49 patients (19 women, 30 men), of whom 39 had resections for a first tumor and 10 had resections for recurrent tumors. The mean age was 55.1 years (range, 30 to 84 years). Patient demographics were similar between the groups in age, Karnofsky Performance Status score, and preoperative tumor volume.

Patients were randomly assigned to iMRI (n = 24) or to conventional microsurgery (n = 25). Intraoperative imaging was performed with a mobile ultra-low-field iMRI device. A single experienced neuroradiologist blinded to treatment modality analyzed high-field preoperative (within 7 days) and postoperative (within 72 hours) magnetic resonance images and calculated residual tumor volumes from triplanar images if the volume was greater than 0.185 cm3.

In the iMRI group, intraoperative imaging revealed residual tumor in 8 patients (33.3%), leading to continued resection. Dr. Senft reported that among the iMRI group, resection was judged complete for 23 (95.8%) and incomplete for 1 (4.2%).

In the conventional surgery group, there were 17 (68%) complete resections and 8 (32.0%) incomplete ones (P < .05).

Residual tumor volumes were a median of less than 0.01 cm3 in the iMRI group (maximum, 0.19 cm3) and a mean of 0.28 cm3 (maximum, 1.76 cm3) in the conventional surgery group (P < .001).

Six months after surgery, twice as many patients in the iMRI group had stable disease as had progressive disease (16 vs 8). In the conventional surgery group, the results were the opposite, with 9 patients experiencing stable disease and 16 progressing (P < .05).

Progression-free survival was 226 days (95% confidence interval [CI], 0 to 454 days) in the iMRI group and 154 days (95% CI, 60 to 248 days) in the conventional surgery group. This difference was not statistically significant. Overall morbidity was low, and there was no difference between groups in terms of patient safety.

"The use of MRI leads to higher rates of tumor resection and lower postop tumor volumes than conventional microsurgery, which in turn leads to improved progression-free survival," Dr. Senft concluded. He added that the extent of resection is the strongest predictor of progression-free survival.

Mitchel Berger, MD, professor and chair of the Department of Neurological Surgery at the University of California, San Francisco, who was not involved in the study, said the study results are consistent with the published literature, which has shown that residual tumor can be detected with iMRI 33% to 81% of the time, guiding further resection 30% to 60% of the time.

One of his criticisms of the study was that although it was prospective and randomized, the fact that it was not blinded could lead to bias. A concern that Dr. Berger voiced was that there was no information about tumor location (eloquent vs noneloquent areas of the brain) or how many were de novo or recurrent in each study group.

"Intraoperative imaging can improve resection rates without changing morbidity beyond conventional microsurgery, which includes navigation," Dr. Berger concluded. "This can be further enhanced by using intraoperative imaging to update existing navigation along with, for example, functional mapping as indicated."

He noted that the utility of iMRI is "quite apparent" for enhancing the extent of resection in low-grade gliomas, but he questioned whether iMRI is better at achieving a maximal resection for high-grade gliomas, compared with the much less expensive fluorescent dye 5-aminolevulinic acid.

Dr. Senft reports receiving an honorarium from Medtronic Navigation. Dr. Berger has disclosed no relevant financial relationships.

American Association of Neurological Surgeons (AANS) 79th Annual Meeting: Plenary session I. Presented April 11, 2011.

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