Commentary: A Novel 5-Aminolevulinic Acid-Enabled Surgical Loupe System—A Consecutive Brain Tumor Series of 11 Cases

Zhang et al¹ reviewed the use of a new commercially available system combining surgical loupes and a headlight with a blue filter to perform fluorescent-guided resection (FGR) of brain tumors which they compared with a standard 5-aminolevulinic acid–enabled surgical microscope. The loupes have 2 built-in filters which block the lights from the excitation wavelength generated by the headlight that has both a white light and 2 different wavelengths of blue light that can be alternated with a wireless foot pedal. The authors found that the system was easy to use with less interference with the surgical workflow than the use of a surgical microscope and provided the additional advantage of more rapid switching between white and blue light modes. The fluorescence was also subjectively brighter under loupes than with the microscope.

The primary objective of this technology, as stated by the authors, is “maximal safe resection” of malignant gliomas which has been linked to improved survival in both prospective case series² and unbiased statistical analysis of large prospective studies^3,4 as well as previous series of 5-aminolevulinic acid FGR which demonstrated increased progression-free survival and overall survival.^5,6 Other approaches to maximizing maximal safe resection include FGR using other nontargeted fluorescence agents such as fluorescein sodium, indocyanine green, chorotoxin derivatives,⁶ and various fluorescent agents, currently in development.⁸ Novel approaches to visualization include the use of handheld probes,⁹ as well as endoscopes¹⁰ and exoscopes.¹¹

Ultimately, the importance of this loupe-based system may prove to be the simplicity and improved “ease of use” relative to the use of a specially modified surgical microscope rather than the subjectively improved visualization noted by the authors. Although 5-aminolevulinic acid was approved by the European Medicines Agency in 2007, it was not approved by the Food and Drug Administration (FDA) until 2017 and is still not universally adopted in the United States. This is likely due in part to the requirement that surgical microscopes be modified for FGR and used in such cases, adding surgical time and effort as well as institutional expense.

Similarly, stereotaxis was initially the domain of functional neurosurgeons and those with engineering backgrounds until the advent of frameless stereotaxy in the early to mid 1990s streamlined registration and commercial adoption making it easier to use.¹² It is now the standard tool of neurosurgical oncology. Given an increased emphasis on “value-based care” in medicine and increased appreciation for the scarcity of healthcare resources accentuated by the current coronavirus disease 2019 pandemic, any approach that saves time and effort with similar or improved clinical outcomes is likely to be more readily adopted. Thus, this specially modified loupe system, which eliminates the need for expensive and sometimes unwieldy surgical microscopes and additional steps before use including balancing, draping, and moving the device into the field, may speed adoption of FGR. This will likely benefit patients, surgeons, and the healthcare system.

Funding

This study did not receive any funding or financial support. Dr Sloan has funding from NIH and Monteris Medical.

Disclosures

The author has no personal, financial or institutional interest in any of the drugs, materials, or devices described in this article. Dr Sloan serves as Co-PI of a grant on the topic of fluorescence-guided imaging and have written about it in the past.