Each year, over 15 000 patients undergo resection of brain tumors in the United States. 1 During surgery, identifying margins of brain tumors, particularly glioblastomas (GBMs) and highly invasive neoplasms, remains a technical challenge. Thus, for both benign and malignant brain tumors, the most common cause of relapse is local recurrence at the resection margins. At the time of the operation, surgeons typically use visual inspection and tactile discrimination to differentiate tumor margins from surrounding normal brain parenchyma. In addition, imaging adjuncts such as navigation and intraoperative ultrasound can provide value. However, this method has many limitations, which accounts for the high rate of local failure.
Intraoperative adjunctive technologies, such as imaging-based navigational systems, have been useful in allowing the surgeon to estimate areas of contrast enhancement, which likely represent tumor. Although ultrasound-based re-registration can be used to account for brain shift, navigation alone is hampered by the inaccuracies attributable to brain shift and poor resolution when performing surgery in vivo. For the past 2 decades, intraoperative fluorescent contrast agents have been proposed to aid the neurosurgeon in identifying tumor tissue during surgery. The most popular approach has been fluorescent-guided intraoperative imaging with 5-aminolevulinic acid (5-ALA). This method has been studied since the 1990s. 2-4 5-ALA is a pro-drug in the porphyrin family that facilitates tumor identification; its use improves gross total resection rates and prolongs progression-free survival in patients with high-grade gliomas. 3 Despite its benefits, 5-ALA has not reached widespread popularity in the United States, primarily because of lack of Food and Drug Administration (FDA) approval. Even if it were approved, 5-ALA does have specific limitations including low depth of penetration, autofluorescence of background parenchyma, and elevated liver enzymes possibly contributing to hepatotoxicity. In addition to 5-ALA, additional investigators have explored fluorescein as well as novel near-infrared (NIR) agents. 5-7
From Intraoperative Near-Infrared Optical Imaging Can Localize Gadolinium-Enhancing Gliomas During Surgery by Lee, John Y.K. MD, MSCE; Thawani, Jayesh P. MD; Pierce, John MS; Zeh, Ryan BA; Martinez-Lage, Maria MD; Chanin, Michelle BA; Venegas, Ollin BA; Nims, Sarah BA; Learned, Kim BA; Keating, Jane MD; Singhal, Sunil MD