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Imaging Agent Greatly Improves Surgeon's Ability to See Gliomas Intraoperatively: Presented at AANS

By Cameron Johnston

NEW ORLEANS -- April 19, 2005 -- Using a synthetically produced amino acid known as 5-aminolevulinic acid (5-ALA), has allowed surgeons to intraoperatively visualize malignant gliomas and to achieve complete removal of the tumours.

In a presentation here on April 18^th at the 73^rd meeting of the American Association of Neurological Surgeons, Dr. Walter Stummer, neurosurgeon, Universitatsklinikum, Dusseldorf, Germany, explained that part of the problem in treating malignant gliomas surgically is that it is difficult to discern the margins of the tumours. Therefore, some degree of residual tumour is often left in place, and the patient's likelihood of recurrence is significantly greater.

5-ALA is a naturally occurring amino acid and is a precursor to the red coloring that gives red blood cells their color, Dr. Stummer explained. When 5-ALA is taken up by a cancerous tumour, it becomes highly fluorescent, thus allowing surgeons to visualize more precisely the margins of the tumour and remove it during re-sectioning.

The 5-ALA used in this study was synthesized by Medac, of Wedel, Germany.

In Dr. Stummer's study, patients with gliomas were divided into two groups, one given 5-ALA 20 mg/kg body weight orally 3 hours before anesthesia, and the other given standard white illumination.

No residual enhancing tumor was found in 65% of patients in the ALA group compared to 36% in the white light group (P < .001).

Progression-free survival was superior in 5-ALA compared to white illumination patients (P < .01), with cumulative 6-month progression-free survival rates of 41% and 21%, respectively. The benefit was particularly evident in the subgroup of patients aged 55 and older (11.5 vs. 13.8 months). This in itself may be an important finding in that gliomas occur most frequently in this age group.

Patients in the 55-plus age group also had less repeat surgery compared with those who were younger than 55 years, Dr. Stummer said.

Although these overall survival results were not statistically significant, this was in part due to the small number of patients in the study, he explained. Nonetheless, a more complete removal of the tumour, as seen on post-operative magnetic resonance imaging (MRI), was associated with improved survival. Those with no residual tumor visible on MRI had significantly longer median survival times than patients who showed residual tumor.

The study presented at the AANS meeting was also a preliminary analysis. Dr. Stummer said that since then, surgery has been performed on "at least a thousand" patients who were pre-treated with 5-ALA. The company expects to file for approval from European authorities and from the U.S. Food and Drug Administration in mid-2005, he said.


[Presentation title: Multicentric Phase III Study on Fluorescence-Guided Resection of Malignant Gliomas with 5-ASA: Preliminary Results on Interim Analysis of 270 Patients. Abstract 708]

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