Use of a Single-Fibre Optical Probe for the Detection of Tumour Fluorescence in High Grade Glioma

Introduction: High grade glioma is the most common primary brain tumour in adults. The overall median survival is between 14-16 months. Fluorescence guided surgery by detection of PpIX fluorescence has been shown to improve extent of resection, translating to improved progression-free survival. PpIX is also known to accumulate at lower concentrations in low grade glioma. Microscope-based fluorescence detection techniques are associated with several pain-points, some of which may be addressed by using contact-based spectroscopy. We aimed to investigate the accuracy of an optical fibre at detecting PpIX fluorescence by performing real-time spectroscopy in patients with high grade glioma.

Methods: Adult patients undergoing fluorescence-guided surgery for suspected high grade glioma were recruited prospectively. Intra-operatively, samples from cortex, white matter and tumour were taken. These samples were interrogated using standard white and blue light microscopic techniques, and the optical fibre. These specimens were then assessed by neuropathology to determine whether tumour tissue was present within them.

Results: We collected 89 samples from 28 patients. There was an equal ratio of males to females, with a median age of 66.5 years. The accuracy of the probe for detecting PpIX fluorescence was 75.9%, compared with 56.6% for the operating microscope.

Conclusion : The optical fibre probe was more accurate than the operating microscope for detecting PpIX fluorescence. This technology has potential value in improving the accuracy of fluorescence-guided surgery and has potential practical benefits relating to surgical workflow. It may also prove valuable for other indications such as surgery for low grade glioma, although further research into this is required.