Introduction: Fluorescent-guided surgery (FGS) after 5-aminolevulinic acid (5-ALA) administration has been shown to result in more complete resection of malignant gliomas. Blue light (410 nm) emitted from the intraoperative microscope permits gross intraoperative visualization of protoporphorin IX (PpIX), metabolized from 5-ALA, in malignant glioma tissues. We have recently developed a hand-held spectroscopic pen device for intraoperative tumor detection based on wavelength-resolved measurements of fluorescent signals. Here, we present the use of this device for ultrasensitive GBM tumor cell detection in vitro and vivo after 5-ALA administration.
Methods: A spectroscopic device with violet LED excitation and a fiber optic probe was constructed. An in vitro study was conducted to test the sensitivity of this device with human GBM cells after 5-ALA treatment. Intracranial human GBM xenografts generated in rodents were also used to determine in vivo fluorescent measurements and sensitivity. Measurements were performed on xenografts and normal brain 24 h after 5-ALA administration. Human GBM tumor specimens were also collected from newly diagnosed human patients enrolled in a Phase II 5-ALA study undergoing FGS of their tumor. Specimens were collected from 4 different regions of the tumor corresponding to the tumor bulk, necrosis, perinecrosis, and tumor margin. The specimens were analyzed ex vivo using the device to analyze PpIX signal.
Results: Sensitivity studies showed that the handheld pen device is capable of detecting <1000 tumor cells. Measurements in human specimens showed intense fluorescent signal from the tumor margin, bulk and perinecrotic regions while weak signal was found in the necrotic core. Analysis showed a >40:1 signal:noise ratio.
Conclusions: These studies demonstrate the potential of the device for intraoperative differentiation of tumor and normal tissue that is not possible with visual observation with the modified intraoperative microscope. Future work includes continued refinement of the device and a clinical trial for intraoperative guidance in glioblastoma resection.
Patient Care: Fluorescent guided surgery (FGS) permits more complete resection of malignant gliomas. Future handheld devices may further optimize resection of malignant gliomas.
Learning Objectives: 1.Understand use of 5-ALA and fluorescent-guided surgery for more complete resection of malignant gliomas.
2.Introduction of hand-held spectroscopy device for PpIX fluorescence detection.
3. Use of hand-held device for detection of <1000 GBM cells and orthotopic human GBM xenografts.
4. Use of hand-held device for intraoperative fluorescence of different regions of GBM tumor (tumor margin, bulk, and perinecrotic areas).