Fluorescence form 5-aminolevulinic acid (5-ALA) has been used to guide resection of recurrent glioblastoma multiforme (GBM). Before surgery, the patient ingests 5-ALA, then the tumor cells fluoresce intraoperatively in response to certain wavelengths of light. This can provide information not necessarily available through magnetic resonance imaging (MRI), which is the standard mode of imaging used to detect primary and recurrent GBMs. The additional information provided by 5-ALA fluorescence can guide surgeons in the treatment of individual cases.
GBM is the most common primary tumor of the brain. It is extremely aggressive and is usually treated with resection followed by chemotherapy and radiotherapy. Even using this regimen, patient survival is not long: on average 1 to 2 years. The best way to lengthen survival is to remove as much tumor as possible. This holds for recurrent GBMs as well as for the initial tumor.
A 56-year-old man presented with frequent transient vision disturbances. Seven years earlier, he had undergone gross-total (maximum) resection of a GBM located in the right occipital lobe. A new MRI study was performed, and the images showed three distinct, new sites of tumor in the man’s right temporal lobe. No evidence of recurrent tumor was seen at the site where the original tumor had been located.
The patient in this case was scheduled for surgery to remove the three new lesions. To aid intraoperative visualization of the lesions, the neurosurgical team, led by Mitchel S. Berger, MD, chairman of the Department of Neurological Surgery at the University of California at San Francisco, administered 5-ALA to the patient 4 hours prior to surgery.
During surgery, a blue light was used to activate 5-ALA fluorescence of tumor cells, thus differentiating the tumor from other brain tissue. Using the blue light, the surgeons were also able to detect tumor cells along the lining of the right lateral ventricle, in the ependymal and subependymal regions.
Although the appearance of the three lesions on preoperative MRI had indicated distinct sites of recurrent disease (multicentric tumor recurrence), the fluorescence of tumor cells during surgery mapped out the spread of disease from the original GBM site in the right occipital lobe to three sites in the right temporal lobe through a pathway along the wall of the right ventricle. This showed that the GBM recurrence was not multicentric at all. The fluorescence also made it possible for the surgeons to identify and resect additional tumor tissue along the pathway between the original and recurrent lesions.
According to the authors, MRI is unable to clearly delineate diffuse tumor infiltrating the ependyma and subependymal zone lining the lateral ventricle. However, adding 5-ALA fluorescence during surgery revealed the pathway of tumor spread through these regions. This case study was published in the Journal of Neurosurgery (2013; doi:10.3171/2013.1.JNS121537.).