The value of visible 5-ALA fluorescence and quantitative protoporphyrin IX analysis for improved surgery of suspected low-grade gliomas

Abstract

<jats:sec><jats:title>OBJECTIVE</jats:title><jats:p>In patients with suspected diffusely infiltrating low-grade gliomas (LGG), the prognosis is dependent especially on extent of resection and precision of tissue sampling. Unfortunately, visible 5-aminolevulinic acid (5-ALA) fluorescence is usually only present in high-grade gliomas (HGGs), and most LGGs cannot be visualized. Recently, spectroscopic probes were introduced allowing in vivo quantitative analysis of intratumoral 5-ALA–induced protoporphyrin IX (PpIX) accumulation. The aim of this study was to intraoperatively investigate the value of visible 5-ALA fluorescence and quantitative PpIX analysis in suspected diffusely infiltrating LGG.</jats:p></jats:sec><jats:sec><jats:title>METHODS</jats:title><jats:p>Patients with radiologically suspected diffusely infiltrating LGG were prospectively recruited, and 5-ALA was preoperatively administered. During resection, visual fluorescence and absolute tissue PpIX concentration (C<jats:sub>PpIX</jats:sub>) measured by a spectroscopic handheld probe were determined in different intratumoral areas. Subsequently, corresponding tissue samples were safely collected for histopathological analysis. Tumor diagnosis was established according to the World Health Organization 2016 criteria. Additionally, the tumor grade and percentage of tumor cells were investigated in each sample.</jats:p></jats:sec><jats:sec><jats:title>RESULTS</jats:title><jats:p>All together, 69 samples were collected from 22 patients with histopathologically confirmed diffusely infiltrating glioma. Visible fluorescence was detected in focal areas in most HGGs (79%), but in none of the 8 LGGs. The mean C<jats:sub>PpIX</jats:sub> was significantly higher in fluorescing samples than in nonfluorescing samples (0.693 μg/ml and 0.008 μg/ml, respectively; p &lt; 0.001). A significantly higher mean percentage of tumor cells was found in samples with visible fluorescence compared to samples with no fluorescence (62% and 34%, respectively; p = 0.005), and significant correlation of C<jats:sub>PpIX</jats:sub> and percentage of tumor cells was found (r = 0.362, p = 0.002). Moreover, high-grade histology was significantly more common in fluorescing samples than in nonfluorescing samples (p = 0.001), whereas no statistically significant difference in mean C<jats:sub>PpIX</jats:sub> was noted between HGG and LGG samples. Correlation between maximum C<jats:sub>PpIX</jats:sub> and overall tumor grade was highly significant (p = 0.005). Finally, 14 (40%) of 35 tumor samples with no visible fluorescence and 16 (50%) of 32 LGG samples showed significantly increased C<jats:sub>PpIX</jats:sub> (cutoff value: 0.005 μg/ml).</jats:p></jats:sec><jats:sec><jats:title>CONCLUSIONS</jats:title><jats:p>Visible 5-ALA fluorescence is able to detect focal intratumoral areas of malignant transformation, and additional quantitative PpIX analysis is especially useful to visualize mainly LGG tissue that usually remains undetected by conventional fluorescence. Thus, both techniques will support the neurosurgeon in achieving maximal safe resection and increased precision of tissue sampling during surgery for suspected LGG.</jats:p><jats:p>Clinical trial registration no.: NCT01116661 (clinicaltrials.gov)</jats:p></jats:sec>

TCGA mRNA Expression Analysis of the Heme Biosynthesis Pathway in Diffusely Infiltrating Gliomas: A Comparison of Typically 5-ALA Fluorescent and Non-Fluorescent Gliomas

“…As a consequence, a significantly higher rate of complete resections and prolonged progression-free survival was found in patients suffering from WHO grade IV gliomas after 5-ALA fluorescence-guided resection [ 16 ]. In contrast, visible 5-ALA fluorescence is only rarely detectable in WHO grade II gliomas and thus this technique is usually unable to improve the EOR in such tumors [ 12 , 21 ]. Initially, a breakdown of the blood brain barrier (BBB) resulting in distinct leakage of contrast-enhancement (CE) on MRI was believed to be essential for presence of visible 5-ALA fluorescence [ 20 , 22 ].…”

“…Aside from neuronavigation, ultrasound and intraoperative magnetic resonance imaging (MRI), fluorescence-guided surgery using 5-aminolevulinic acid (5-ALA) is a powerful method for improved visualization of high-grade gliomas (HGG; WHO grade III and IV) and is thus nowadays widely used [ 8 , 9 , 10 , 11 ]. In contrast to HGG, visible fluorescence is frequently absent in low-grade gliomas (LGG; WHO grade II) [ 12 , 13 ]. However, subvisual 5-ALA fluorescence is present also in LGG based on spectroscopic analyses [ 13 , 14 , 15 ].…”

Blood-Brain Barrier, Blood-Brain Tumor Barrier, and Fluorescence-Guided Neurosurgical Oncology: Delivering Optical Labels to Brain Tumors

“…So far, it is hard to elucidate which mechanism is most determinate of 5-ALA accumulation. Observed foci of fluorescence in low-grade gliomas were correlated with anaplastic transformation and increased cellularity (216,217), which in turn may result in a less competent BBTB that is permeable to 5-ALA but not to gadolinium-based contrast.…”

Fluorescence image-guided surgery: a perspective on contrast agent development

“…5-ALA is metabolized to the fluorescent porphyrin molecule PpIX following uptake in cancer cells, possessing visible fluorescence with excitation at 380-440 nm and emission at 620-640 nm. 39,40 5-ALA was first studied for FGS in 1998 and reached FDA approval in 2017. 41 Remarkably, 5-ALA enabled FGS has improved high grade glioma complete resection rates almost two-fold over white light imaging alone, resulting in increased overall progression free survival.…”