Fluorescence of non-neoplastic, magnetic resonance imaging-enhancing tissue by 5-aminolevulinic acid: case report

Sonodynamic Therapy and Sonosensitizers for Glioma Treatment: A Systematic Qualitative Review

Sonodynamic therapy (SDT) has emerged as an encouraging noninvasive technique that uses ultrasound to activate targeted agents to induce antitumor effects for the treatment of glioma. With extensive variation in the types of sonosensitizers, protocols for sonication, and model systems, a comprehensive overview of existing preclinical data on the efficacy of SDT in glioma treatment is warranted. Here, we conduct a systematic review of preclinical and early clinical literature on implementing SDT to treat in vitro and in vivo models of glioma. Our findings suggest that coupling sonosensitizers such as 5-aminolevulinic acid, hematoporphyrin monomethyl ether, and sinoporphyrin sodium with focused ultrasound induces robust cytotoxic activity in tumor cells (in vitro and in vivo). These effects are likely mediated by the oxidative stress induced by reactive oxygen species production, apoptotic signaling cascades, and intracellular calcium overload. Future research is needed to better understand the biochemical and mechanistic properties of SDT, and ongoing trials may help elucidate the clinical feasibility of glioma treatment with optimized sonically activated treatments.

5-Aminolevulinic acid fluorescence in brain non-neoplastic lesions: a systematic review and case series

Fluorescence-guided surgery with 5-aminolevulinic acid (5-ALA) is used to assist brain tumor resection, especially for high-grade gliomas but also for low-grade gliomas, metastasis, and meningiomas. With the increasing use of this technique, even to assist biopsies, high-grade glioma-mimicking lesions had misled diagnosis by showing 5-ALA fluorescence in non-neoplastic lesions such as radiation necrosis and inflammatory or infectious disease. Since only isolated reports have been published, we systematically review papers reporting non-neoplastic lesion cases with 5-ALA according with the PRISMA guidelines, present our series, and discuss its pathophysiology. In total, 245 articles were identified and 12 were extracted according to our inclusion criteria. Analyzing 27 patients, high-grade glioma was postulated as preoperative diagnosis in 48% of the cases. Microsurgical resection was performed in 19 cases (70%), while 8 patients were submitted to biopsy (30%). We found 4 positive cases in demyelinating disease (50%), 4 in brain abscess (80%), 1 in neurocysticercosis (33%), 1 in neurotoxoplasmosis, infarction, and hematoma (100%), 4 in inflammatory disease (80%), and 3 in cortical dysplasia (100%). New indications are being considered especially in benign lesion biopsies with assistance of 5-ALA. Using fluorescence as an aid in biopsies may improve procedure time, number of samples, and necessity of intraoperative pathology. Further studies should include this technology to encourage more beneficial uses.

5-Aminolevulinic Acid-Induced Protoporphyrin IX Fluorescence Imaging for Tumor Detection: Recent Advances and Challenges

5-Aminolevulinic acid (5-ALA) is a natural amino acid and a precursor of heme and chlorophyll. Exogenously administered 5-ALA is metabolized into protoporphyrin IX (PpIX). PpIX accumulates in cancer cells because of the low activity of ferrochelatase, an enzyme that metabolizes PpIX to heme. High expression of 5-ALA influx transporters, such as peptide transporters 1/2, in cancer cells also enhances PpIX production. Because PpIX radiates red fluorescence when excited with blue/violet light, 5-ALA has been used for the visualization of various tumors. 5-ALA photodynamic diagnosis (PDD) has been shown to improve the tumor removal rate in high-grade gliomas and non-muscular invasive bladder cancers. However, 5-ALA PDD remains a challenge as a diagnostic method because tissue autofluorescence interferes with PpIX signals in cases where tumors emit only weak signals, and non-tumorous lesions, such as inflammatory sites, tend to emit PpIX fluorescence. Here, we review the current outline of 5-ALA PDD and strategies for improving its diagnostic applicability for tumor detection, focusing on optical techniques and 5-ALA metabolic pathways in both viable and necrotic tumor tissues.

Accumulation of Uroporphyrin I in Necrotic Tissues of Squamous Cell Carcinoma after Administration of 5-Aminolevulinic Acid

5-aminolevulinic acid (5-ALA)-induced protoporphyrin IX (PpIX) fluorescence is widely used for the intraoperative detection of malignant tumors. However, the fluorescence emission profiles of the accompanying necrotic regions of these tumors have yet to be determined. To address this, we performed fluorescence and high-performance liquid chromatography (HPLC) analyses of necrotic tissues of squamous cancer after 5-ALA administration. In resected human lymph nodes of metastatic squamous cell carcinoma, we found a fluorescence peak at approximately 620 nm in necrotic lesions, which was distinct from the PpIX fluorescence peak at 635 nm for viable cancer lesions. Necrotic lesions obtained from a subcutaneous xenograft model of human B88 oral squamous cancer also emitted the characteristic fluorescence peak at 620 nm after light irradiation: the fluorescence intensity ratio (620 nm/635 nm) increased with the energy of the irradiation light. HPLC analysis revealed a high content ratio of uroporphyrin I (UPI)/total porphyrins in the necrotic cores of murine tumors, indicating that UPI is responsible for the 620 nm peak. UPI accumulation in necrotic tissues after 5-ALA administration was possibly due to the failure of the heme biosynthetic pathway. Taken together, fluorescence imaging of UPI after 5-ALA administration may be applicable for the evaluation of tumor necrosis.

Fluorescence-Guided Surgery for High-Grade Gliomas: State of the Art and New Perspectives

High-grade gliomas are aggressive tumors that require multimodal management and gross total resection is considered to be the first crucial step of treatment. Because of their infiltrative nature, intraoperative differentiation of neoplastic tissue from normal parenchyma can be challenging. For these reasons, in the recent years, neurosurgeons have increasingly performed this surgery under the guidance of tissue fluorescence. Sodium fluoresceine and 5-aminolevulinic acid represent the 2 main compounds that allow real-time identification of residual malignant tissue and have been associated with improved gross total resection and radiological outcomes. Though presenting different profiles of sensitivity and specificity and further investigations concerning cost-effectiveness are need, Sodium fluoresceine, 5-aminolevulinic acid and new phluorophores, such as Indocyanine green, represent some of the most important tools in the neurosurgeon’s hands to achieve gross total resection.

5-Aminolevulinic Acid-Induced Fluorescence in Focal Cortical Dysplasia: Report of 3 Cases

BACKGROUND

Three patients enrolled in a clinical trial of 5-aminolevulinic-acid (5-ALA)-induced fluorescence-guidance, which has been demonstrated to facilitate intracranial tumor resection, were found on neuropathological examination to have focal cortical dysplasia (FCD).

OBJECTIVE

To evaluate in this case series visible fluorescence and quantitative levels of protoporphyrin IX (PpIX) during surgery and correlate these findings with preoperative magnetic resonance imaging (MRI) and histopathology.

METHODS

Patients were administered 5-ALA (20 mg/kg) approximately 3 h prior to surgery and underwent image-guided, microsurgical resection of their MRI- and electrophysiologically identified lesions. Intraoperative visible fluorescence was evaluated using an operating microscope adapted with a commercially available blue light module. Quantitative PpIX levels were assessed using a handheld fiber-optic probe and a wide-field imaging spectrometer. Sites of fluorescence measurements were co-registered with both preoperative MRI and histopathological analysis.

RESULTS

Three patients with a pathologically confirmed diagnosis of FCD (Types 1b, 2a, and 2b) underwent surgery. All patients demonstrated some degree of visible fluorescence (faint or moderate), and all patients had quantitatively elevated concentrations of PpIX. No evidence of neoplasia was identified on histopathology, and in 1 patient, the highest concentrations of PpIX were found at a tissue site with marked gliosis but no typical histological features of FCD.

CONCLUSION

FCD has been found to be associated with intraoperative 5-ALA-induced visible fluorescence and quantitatively confirmed elevated concentrations of the fluorophore PpIX in 3 patients. This finding suggests that there may be a role for fluorescence-guidance during surgical intervention for epilepsy-associated FCD.

Near-Infrared Molecular Imaging of Glioblastoma by Miltuximab®-IRDye800CW as a Potential Tool for Fluorescence-Guided Surgery

Glioblastoma (GBM) is one of the most aggressive tumors and its 5-year survival is approximately 5%. Fluorescence-guided surgery (FGS) improves the extent of resection and leads to better prognosis. Molecular near-infrared (NIR) imaging appears to outperform conventional FGS, however, novel molecular targets need to be identified in GBM. Proteoglycan glypican-1 (GPC-1) is believed to be such a target as it is highly expressed in GBM and is associated with poor prognosis. We hypothesize that an anti-GPC-1 antibody, Miltuximab^®, conjugated with the NIR dye, IRDye800CW (IR800), can specifically accumulate in a GBM xenograft and provide high-contrast in vivo fluorescent imaging in rodents following systemic administration. Miltuximab^® was conjugated with IR800 and intravenously administered to BALB/c nude mice bearing a subcutaneous U-87 GBM hind leg xenograft. Specific accumulation of Miltuximab^®-IR800 in subcutaneous xenograft tumor was detected 24 h later using an in vivo fluorescence imager. The conjugate did not cause any adverse events in mice and caused strong fluorescence of the tumor with tumor-to-background ratio (TBR) reaching 10.1 ± 2.8. The average TBR over the 10-day period was 5.8 ± 0.6 in mice injected with Miltuximab^®-IR800 versus 2.4 ± 0.1 for the control group injected with IgG-IR800 (p = 0.001). Ex vivo assessment of Miltuximab^®-IR800 biodistribution confirmed its highly specific accumulation in the tumor. The results of this study confirm that Miltuximab^®-IR800 holds promise for intraoperative fluorescence molecular imaging of GBM and warrants further studies.

5-Aminolevulinic Acid False Positives in Cerebral Neuro-Oncology: Not All That Is Fluorescent Is Tumor. A Case-Based Update and Literature Review

BACKGROUND

One of the most valuable innovations in high-grade glioma surgery is 5-aminolevulinic acid (5-ALA). Fluorescence is a specific and sensitive indicator of metabolically active tumor tissue. In the published literature, the main focus has been placed on false-negative cases, with only a few articles addressing false positivity. The aim of the article was to highlight settings in which 5-ALA fluorescence does not necessarily mean tumor and to point out conditions in which intraoperative 5-ALA fluorescence has to be critically interpreted.

METHODS

Using PubMed, a review of pertinent literature was done to specifically investigate all conditions, including non-neoplastic and other metabolically active lesions, that can mimic high-grade gliomas and cause a misleading intraoperative diagnosis. In addition, an institutional case characterized by strong 5-ALA fluorescence in radionecrosis is presented.

RESULTS

Literature results were grouped in 2 main categories according to the field of application: oncologic setting (9 articles and 1 institutional case) and nononcologic settings (5 articles).

CONCLUSIONS

As reported, 5-ALA-induced fluorescence is not limited to glioma but is also evident in nonglioma and non-neoplastic conditions. Critical interpretation of intraoperative fluorescence is therefore mandatory in recurrences and in atypical cases that might hinder alternative diagnoses.

Spectral Radiance of Protoporphyrin IX Fluorescence and Its Histopathological Implications in 5-Aminolevulinic Acid-Guided Surgery for Glioblastoma

OBJECTIVE

This study is intended to objectively clarify the relationship between the fluorescence intensity emitted by protoporphyrin IX (PpIX), which is a metabolite of 5-aminolevulinic acid (ALA), and histological findings during glioblastoma surgery.

BACKGROUND

ALA is widely used for the intraoperative detection of tumors. There are several reports about the fluorescence of PpIX and the histological findings of tumors, but judgments about the fluorescence intensity depend largely on the subjective sense of each surgeon.

METHODS

We quantified the PpIX fluorescence intensity emitted from tissue specimens using a spectroradiometer and evaluated the relationship between a spectral radiance of 635 nm and the histopathological features of surgical specimens of glioblastoma. Surgical samples from glioblastoma patients consist of a strongly fluorescent area (SFA) or vaguely fluorescent area (VFA). Hematoxylin and eosin staining, immunohistochemical Ki-67, and CD31 staining were performed to evaluate the cell density, MIB-1 index, and vascularity, respectively. The fluorescence intensities of each sample were compared with each histopathological parameter.

RESULTS

Cell density, MIB-1 index, and total vascular area were significantly correlated with PpIX fluorescence radiance. 87.5% of SFA were judged to be tumor bulk consisting mostly of tumor cells and 12.5% peritumoral invaded brain. In the VFA, 100% of specimens were judged to be peritumoral invaded brain.

CONCLUSIONS

ALA-induced PpIX fluorescence has quantitatively correlated well with histopathological malignant features both in SFA and VFA. These findings suggest that not only SFA but also VFA should be removed to the highest extent that does not cause neurological symptoms.

First-in-human intraoperative near-infrared fluorescence imaging of glioblastoma using cetuximab-IRDye800

Introduction

Maximizing extent of surgical resection with the least morbidity remains critical for survival in glioblastoma patients, and we hypothesize that it can be improved by enhancements in intraoperative tumor detection. In a clinical study, we determined if therapeutic antibodies could be repurposed for intraoperative imaging during resection.

Methods

Fluorescently labeled cetuximab-IRDye800 was systemically administered to three patients 2 days prior to surgery. Near-infrared fluorescence imaging of tumor and histologically negative peri-tumoral tissue was performed intraoperatively and ex vivo. Fluorescence was measured as mean fluorescence intensity (MFI), and tumor-to-background ratios (TBRs) were calculated by comparing MFIs of tumor and histologically uninvolved tissue.

Results

The mean TBR was significantly higher in tumor tissue of contrast-enhancing (CE) tumors on preoperative imaging (4.0 ± 0.5) compared to non-CE tumors (1.2 ± 0.3; p = 0.02). The TBR was higher at a 100 mg dose than at 50 mg (4.3 vs. 3.6). The smallest detectable tumor volume in a closed-field setting was 70 mg with 50 mg of dye and 10 mg with 100 mg. On sections of paraffin embedded tissues, fluorescence positively correlated with histological evidence of tumor. Sensitivity and specificity of tumor fluorescence for viable tumor detection was calculated and fluorescence was found to be highly sensitive (73.0% for 50 mg dose, 98.2% for 100 mg dose) and specific (66.3% for 50 mg dose, 69.8% for 100 mg dose) for viable tumor tissue in CE tumors while normal peri-tumoral tissue showed minimal fluorescence.

Conclusion

This first-in-human study demonstrates the feasibility and safety of antibody based imaging for CE glioblastomas.

False-positive inflammatory change mimicking glioblastoma multiforme under 5-aminolevulinic acid-guided surgery: A case report

Background:

5-aminolevulinic acid (5-ALA)–guided surgery is one of the gold standard perioperative modalities for maximum resection of malignant gliomas. However, it should be noted that 5-ALA fluorescence does not definitively indicate the presence of malignant tumor cells.

Case Description:

We report a rare case of false-positive lesion mimicking glioblastoma multiforme (GBM) under 5-ALA-guided surgery. A 44-year-old woman presented with persistent headache and flickering in her eyes. Magnetic resonance imaging showed enhanced lesion with perifocal edema in the left occipital lobe. We performed 5-ALA-guided surgery for the lesion, during which strong fluorescence was observed, but evaluation of the intraoperative frozen section revealed only inflammatory cells. We concluded the tumor resection once adequate decompression had been achieved, and made the final pathological diagnosis of inflammatory change following an unknown infection.

Conclusion:

Neurosurgeons should be aware of false-positive lesions mimicking GBM under 5-ALA guided surgery.

Intraoperative 5-aminolevulinic acid-induced photodynamic diagnosis of metastatic brain tumors with histopathological analysis

BACKGROUND

Fluorescence-guided surgery using 5-aminolevulinic acid (5-ALA) is a promising real-time navigation method in the surgical resection of malignant gliomas. In order to determine whether this method is applicable to metastatic brain tumors, we evaluated the usefulness of intraoperative fluorescence patterns and histopathological features in patients with metastatic brain tumors.

METHODS

We retrospectively reviewed the cases of 16 patients with metastatic brain tumors who underwent intraoperative 5-ALA fluorescence-guided resection. Patients were given 20 mg/kg of 5-ALA orally 2 h prior to the surgery. High-powered excitation illumination and a low-pass filter (420, 450, or 500 nm) were used to visualize the fluorescence of protoporphyrin IX (PpIX), the 5-ALA metabolite. We evaluated the relationships between the fluorescence and histopathological findings in both tumoral and peritumoral brain tissue.

RESULTS

Tumoral PpIX fluorescence was seen in only 5 patients (31%); in the remaining 11 patients (69%), there was no fluorescence in the tumor bulk itself. In 14 patients (86%), vague fluorescence was seen in peritumoral brain tissue, at a thickness of 2-6 mm. The histopathological examination found cancer cell invasion of adjacent brain tissue in 75% of patients (12/16), at a mean ± SD depth of 1.4 ± 1.0 mm (range 0.2-3.4 mm) from the microscopic border of the tumor. There was a moderate correlation between vague fluorescence in adjacent brain tissue and the depth of cancer cell invasion (P = 0.004).

CONCLUSION

Peritumoral fluorescence may be a good intraoperative indicator of tumor extent, preceding more complete microscopic gross total resection.

TRIAL REGISTRATION

Institutional Review Board of Osaka Medical College No. 42, registered February 17, 1998, and No. 300, registered April 1, 2008. They were retrospectively registered.

5-Aminolevulinic Acid Accumulation in a Cerebral Infarction Mimicking High-Grade Glioma

BACKGROUND

5-Aminolevulinic acid (5-ALA) has become an integral part in the neurosurgical treatment of malignant glioma. Over time, several other tumor entities have been identified to metabolize 5-ALA and show a similar fluorescence pattern during surgical resection. This case report is the first description of 5-ALA accumulation in postischemic cerebral tissue. This evidence questions the assumption that 5-ALA accumulation in glioma is exclusively attributed to tumor infiltration. Instead, 5-ALA accumulation can also occur beyond the tumor borders and may be partially ascribed to inflammatory changes in the surrounding brain tissue.

CASE DESCRIPTION

A 64-year old woman presented with episodes of apraxia and a ring-enhancing lesion in postcontrast T1-weighted magnetic resonance sequences suggestive of high grade glioma. Strong fluorescence was observed during 5-ALA-guided resection. However, although the frozen section was inconclusive, the final histopathologic examination revealed a stage II cerebral infarction.

CONCLUSIONS

5-ALA accumulation in postischemic cerebral tissue should be considered for intended supramarginal resections near eloquent brain regions. Therefore, sufficient preoperative imaging should regularly include magnetic resonance imaging spectroscopy and perfusion sequences to ascertain the proper diagnosis. Moreover, further research is warranted to determine the role of 5-ALA accumulation in postischemic and inflammatory brain tissue.

Role of neurochemical navigation with 5-aminolevulinic acid during intraoperative MRI-guided resection of intracranial malignant gliomas

OBJECTIVE

To evaluate the role of the neurochemical navigation with 5-aminolevulinic acid (5-ALA) during intraoperative MRI (iMRI)-guided resection of the intracranial malignant gliomas.

METHODS

The analysis included 99 consecutive surgical cases. Resection of the bulk of the neoplasm was mainly guided by the updated neuronavigation based on the low-field-strength (0.3T) iMRI, whereas at the periphery of the lesion neurochemical navigation with 5-ALA was additionally used.

RESULTS

In total, 286 tissue specimens were obtained during surgeries for histopathological examination. According to iMRI 98 samples with strong (91 cases), weak (6 cases), or absent (1 case) fluorescence corresponded to the bulk of the lesion and all of those ones contained tumor. Out of 188 tissue specimens obtained from the "peritumoral brain," the neoplastic elements were identified in 89%, 81% and 29% of samples with, respectively, strong (107 cases), weak (47 cases) and absent (34 cases) fluorescence. Positive predictive values of the tissue fluorescence for presence of neoplasm within and outside of its boundaries on iMRI were 100% and 86%, respectively.

CONCLUSION

Neurochemical navigation with 5-ALA is useful adjunct during iMRI-guided resection of intracranial malignant gliomas, which allows identification of the tumor extension beyond its radiological borders.

Pathophysiology, diagnosis, and treatment of radiation necrosis in the brain

New radiation modalities have made it possible to prolong the survival of individuals with malignant brain tumors, but symptomatic radiation necrosis becomes a serious problem that can negatively affect a patient’s quality of life through severe and lifelong effects. Here we review the relevant literature and introduce our original concept of the pathophysiology of brain radiation necrosis following the treatment of brain, head, and neck tumors. Regarding the pathophysiology of radiation necrosis, we introduce two major hypotheses: glial cell damage or vascular damage. For the differential diagnosis of radiation necrosis and tumor recurrence, we focus on the role of positron emission tomography. Finally, in accord with our hypothesis regarding the pathophysiology, we describe the promising effects of the anti-vascular endothelial growth factor antibody bevacizumab on symptomatic radiation necrosis in the brain.

Inflammation as well as angiogenesis may participate in the pathophysiology of brain radiation necrosis

Radiation necrosis (RN) after intensive radiation therapy is a serious problem. Using human RN specimens, we recently proved that leaky angiogenesis is a major cause of brain edema in RN. In the present study, we investigated the same specimens to speculate on inflammation's effect on the pathophysiology of RN. Surgical specimens of symptomatic RN in the brain were retrospectively reviewed by histological and immunohistochemical analyses using hematoxylin and eosin (H&E) staining as well as immunohistochemical staining for VEGF, HIF-1α, CXCL12, CXCR4, GFAP, CD68, hGLUT5, CD45, IL-1α, IL-6 TNF-α and NF-kB. H&E staining demonstrated marked angiogenesis and cell infiltration in the perinecrotic area. The most prominent vasculature was identified as thin-walled leaky angiogenesis, i.e. telangiectasis surrounded by prominent interstitial edema. Two major cell phenotypes infiltrated the perinecrotic area: GFAP-positive reactive astrocytes and CD68/hGLUT5-positive cells (mainly microglias). Immunohistochemistry revealed that CD68/hGLUT5-positive cells and GFAP-positive cells expressed HIF-1α and VEGF, respectively. GFAP-positive cells expressed chemokine CXCL12, and CD68/hGLUT5-positive cells expressed receptor CXCR4. The CD68/hGLUT5-positive cells expressed pro-inflammatory cytokines IL-1α, IL-6 and TNF-α in the perinecrotic area. VEGF caused leaky angiogenesis followed by perilesional edema in RN. GFAP-positive cells expressing CXCL12 might attract CXCR4-expressing CD68/hGLUT5-positive cells into the perinecrotic area. These accumulated CD68/hGLUT5-positive cells expressing pro-inflammatory cytokines seemed to aggravate the RN edema. Both angiogenesis and inflammation might be caused by the regulation of HIF-1α, which is well known as a transactivator of VEGF and of the CXCL12/CXCR4 chemokine axis.

Neurosurgical oncology: advances in operative technologies and adjuncts

Modern glioma surgery has evolved around the central tenet of safely maximizing resection. Recent surgical adjuncts have focused on increasing the maximum extent of resection while minimizing risk to functional brain. Technologies such as cortical and subcortical stimulation mapping, intraoperative magnetic resonance imaging, functional neuronavigation, navigable intraoperative ultrasound, neuroendoscopy, and fluorescence-guided resection have been developed to augment the identification of tumor while preserving brain anatomy and function. However, whether these technologies offer additional long-term benefits to glioma patients remains to be determined. Here we review advances over the past decade in operative technologies that have offered the most promising benefits for glioblastoma patients.

Intraoperative fluorescence-guided resection of high-grade gliomas: a comparison of the present techniques and evolution of future strategies

OBJECTIVE

Fluorescence guidance has a demonstrated potential in maximizing the extent of high-grade glioma resection. Different fluorophores (fluorescent biomarkers), including 5-aminolevulinic acid (5-ALA) and fluorescein, have been examined with the use of several imaging techniques. Our goal was to review the state of this technology and discuss strategies for more widespread adoption.

METHODS

We performed a Medline search using the key words "fluorescence," "intraoperative fluorescence-guided resection," "intraoperative image-guided resection," and "brain glioma" for articles from 1960 until the present. This initial search revealed 267 articles. Each abstract and article was reviewed and the reference lists from select articles were further evaluated for relevance. A total of 64 articles included information about the role of fluorescence in resection of high-grade gliomas and therefore were selectively included for our analysis.

RESULTS

5-ALA and fluorescein sodium have shown promise as fluorescent markers in detecting residual tumor intraoperatively. These techniques have demonstrated a significant increase in the extent of tumor resection. Regulatory barriers have limited the use of 5-ALA and technological challenges have restricted the use of fluorescein and its derivatives in the United States. Limitations to this technology currently exist, such as the fact that fluorescence at tumor margins is not always reliable for identification of tumor-brain interface.

CONCLUSIONS

These techniques are safe and effective for increasing gross total resection. The development of more tumor-specific fluorophores is needed to resolve problems with subjective interpretation of fluorescent signal at tumor margins. Techniques such as quantum dots and polymer or iron oxide-based nanoparticles have shown promise as potential future tools.

Aminolevulinic acid (ALA)-protoporphyrin IX fluorescence guided tumour resection. Part 1: Clinical, radiological and pathological studies

The intraoperative identification and resection of glioma is a significant and important challenge in neurosurgery. Complete resection of the enhancing tumour increases the median survival time in glioblastoma compared to partial glioma resection; however, it is achieved in fewer than half of eligible patients when conventional tumour identification methods are used. Increasing the incidence of complete resection, without causing excess morbidity, requires new methods to accurately identify neoplastic tissue intraoperatively, such as use of the drug 5-amino-levulinic acid (ALA). After ALA ingestion, the fluorescent molecule protoporphyrin IX (PpIX) accumulates in high grade glioma, allowing the neurosurgeon to more easily detect and accurately resect tumour. The utility of ALA has been demonstrated in a large, multicentre phase III randomised control trial of 243 patients with high grade glioma. ALA use led to a significant increase in the incidence of complete resection (65% compared to 36%), improved progression-free survival at 6 months (41% compared to 21%), fewer reinterventions, and delayed onset of neurological deterioration. This review provides a broad assessment of ALA-PpIX fluorescence-guided resection, with Part 1 focusing on its clinical efficacy, and correlations with imaging and histology. The theoretical, biochemical and practical aspects of ALA use are reviewed in Part 2.

Gefitinib enhances the efficacy of photodynamic therapy using 5-aminolevulinic acid in malignant brain tumor cells

BACKGROUND

Since the ATP-binding cassette transporter ABCG2 plays a physiologically significant role of porphyrin efflux from living cells, the expression of ABCG2 may influences the efficacy of photodynamic therapy (PDT). In this study, we evaluated the effect of gefitinib, a potent ABCG2 inhibitor, on 5-aminolevulinic acid (5-ALA)-PDT in brain tumor cell lines in vitro.

MATERIALS AND METHODS

Four human glioma cell lines (U87MG, U118MG, A172, and T98G) and a malignant meningioma cell line (IOMM-Lee) were incubated with gefitinib (0.01-1.0μM) before incubation with 5-ALA (1mM). The effects gefitinib on intracellular protoporphyrin IX (PpIX), mRNA and protein expression of ABCG2, and PDT were evaluated, in vitro.

RESULTS

At concentrations of 0.1μM or higher, gefitinib enhanced intracellular levels of PpIX in a dose-dependent manner in all those cell lines. Gefitinib decreased mRNA and plasma membrane protein expression of ABCG2, and efficiently enhanced the effect of 5-ALA-PDT in malignant brain tumor cells.

CONCLUSION

Gefitinib can inhibit ABCG2-mediated PpIX efflux from malignant brain tumor cells to increase the intracellular PpIX and thereby enhance the PDT effect.

Fluorescence Lifetime Spectroscopy and Imaging in Neurosurgery

Clinical outcome of patients diagnosed with primary brain tumor has been correlated with the extent of surgical resection. In treating this disease, the neurosurgeon must balance between an aggressive, radical resection and minimizing the loss of healthy, functionally significant brain tissue. Numerous intra-operative methodologies and technological approaches have been explored as a means to improve the accuracy of surgical resection. This paper presents an overview of current conventional techniques and new emerging technologies with potential to impact the area of image-guided surgery of brain tumors. Emphasis is placed on techniques based on endogenous fluorescence lifetime contrast and their potential for intraoperative diagnosis of brain tumors.

Fluorescence and image guided resection in high grade glioma

The extent of resection in high grade glioma is increasingly been shown to positively effect survival. Nevertheless, heterogeneity and migratory behavior of glioma cells make gross total resection very challenging. Several techniques were used in order to improve the detection of residual tumor. Aim of this study was to analyze advantages and limitations of fluorescence and image guided resection. A multicentric prospective study was designed to evaluate the accuracy of each method. Furthermore, the role of 5-aminolevulinc acid and neuronavigation were reviewed. Twenty-three patients harboring suspected high grade glioma, amenable to complete resection, were enrolled. Fluorescence and image guides were used to perform surgery. Multiple samples were obtained from the resection cavity of each lesion according to 5-ALA staining positivity and boundaries as delineated by neuronavigation. All samples were analyzed by a pathologist blinded to the intra-operative labeling. Decision-making based on fluorescence showed a sensitivity of 91.1% and a specificity of 89.4% (p<0.001). On the other hand, the image-guided resection accuracy was low (sensitivity: 57.8%; specificity: 57.4%; p=0.346). We observed that the sensitivity of 5-ALA can be improved by the combined use of neuronavigation, but this leads to a significant reduction in specificity. Thus, the use of auxiliary techniques should always be subject to critical skills of the surgeon. We advocate a large-scale study to further improve the assessment of multimodal approaches.

Impact of albumin on drug delivery--new applications on the horizon

Over the past decades, albumin has emerged as a versatile carrier for therapeutic and diagnostic agents, primarily for diagnosing and treating diabetes, cancer, rheumatoid arthritis and infectious diseases. Market approved products include fatty acid derivatives of human insulin or the glucagon-like-1 peptide (Levemir(®) and Victoza(®)) for treating diabetes, the taxol albumin nanoparticle Abraxane(®) for treating metastatic breast cancer which is also under clinical investigation in further tumor indications, and (99m)Tc-aggregated albumin (Nanocoll(®) and Albures(®)) for diagnosing cancer and rheumatoid arthritis as well as for lymphoscintigraphy. In addition, an increasing number of albumin-based or albumin-binding drugs are in clinical trials such as antibody fusion proteins (MM-111) for treating HER2/neu positive breast cancer (phase I), a camelid albumin-binding nanobody anti-HSA-anti-TNF-α (ATN-103) in phase II studies for treating rheumatoid arthritis, an antidiabetic Exendin-4 analog bound to recombinant human albumin (phase I/II), a fluorescein-labeled albumin conjugate (AFL)-human serum albumin for visualizing the malignant borders of brain tumors for improved surgical resection, and finally an albumin-binding prodrug of doxorubicin (INNO-206) entering phase II studies against sarcoma and gastric cancer. In the preclinical setting, novel approaches include attaching peptides with high-affinity for albumin to antibody fragments, the exploitation of albumin-binding gadolinium contrast agents for magnetic resonance imaging, and physical or covalent attachment of antiviral, antibacterial, and anticancer drugs to albumin that are permanently or transiently attached to human serum albumin (HSA) or act as albumin-binding prodrugs. This review gives an overview of the expanding field of preclinical and clinical drug applications and developments that use albumin as a protein carrier to improve the pharmacokinetic profile of the drug or to target the drug to the pathogenic site addressing diseases with unmet medical needs.

Protoporphyrin IX fluorescence contrast in invasive glioblastomas is linearly correlated with Gd enhanced magnetic resonance image contrast but has higher diagnostic accuracy

The sensitivity and specificity of in vivo magnetic resonance (MR) imaging is compared with production of protoporphyrin IX (PpIX), determined ex vivo, in a diffusely infiltrating glioma. A human glioma transfected with green fluorescent protein, displaying diffuse, infiltrative growth, was implanted intracranially in athymic nude mice. Image contrast from corresponding regions of interest (ROIs) in in vivo MR and ex vivo fluorescence images was quantified. It was found that all tumor groups had statistically significant PpIX fluorescence contrast and that PpIX contrast demonstrated the best predictive power for tumor presence. Contrast from gadolinium enhanced T1-weighted (T1W+Gd) and absolute T2 images positively predicted the presence of a tumor, confirmed by the GFP positive (GFP+) and hematoxylin and eosin positive (H&E+) ROIs. However, only the absolute T2 images had predictive power from controls in ROIs that were GFP+ but H&E negative. Additionally, PpIX fluorescence and T1W+Gd image contrast were linearly correlated in both the GFP+ (r = 0.79, p<1×10(-8)) and H&E+ (r = 0.74, p<0.003) ROIs. The trace diffusion images did not have predictive power or significance from controls. This study indicates that gadolinium contrast enhanced MR images can predict the presence of diffuse tumors, but PpIX fluorescence is a better predictor regardless of tumor vascularity.

Enhanced expression of coproporphyrinogen oxidase in malignant brain tumors: CPOX expression and 5-ALA-induced fluorescence

In photodynamic diagnosis, 5-aminolevulinic acid (5-ALA) is widely used for the fluorescence-guided resection of malignant brain tumors, where 5-ALA is converted to protoporphyrin IX, which exhibits strong fluorescence. Little is known, however, about the detailed molecular mechanisms underlying 5-ALA-induced fluorescence. To resolve this issue, we analyzed transcriptome profiles for the genes encoding enzymes, transporters, and a transcription factor involved in the porphyrin-biosynthesis pathway. By quantitative real-time (qRT)-PCR, we measured the mRNA levels of those genes in a total of 20 tumor samples that had been surgically resected from brain tumor patients at the Department of Neurosurgery of Osaka Medical College from 2008 to 2009. We selected 10 tumor samples with no 5-ALA-induced fluorescence, among which 2 were glioblastomas and 8 were metastatic brain tumors. Another 10 tumor samples were selected with strong fluorescence, among which 7 were glioblastomas and 3 were metastatic brain tumors. The qRT-PCR analysis study of these latter 10 samples revealed predominantly high levels of the mRNA of the coproporphyrinogen oxidase (CPOX) gene. The high mRNA level of CPOX expression was significantly well correlated with the phenotype of strong 5-ALA-induced fluorescence (P = .0003). These findings were further confirmed by immunohistochemical studies with a CPOX-specific antibody. It is concluded that induction of CPOX gene expression is one of the key molecular mechanisms underlying the 5-ALA-induced fluorescence of malignant brain tumors. The induction mechanism for the CPOX gene in brain tumors remains to be elucidated.

The distribution of vascular endothelial growth factor-producing cells in clinical radiation necrosis of the brain: pathological consideration of their potential roles

The cell type and localization of vascular endothelial growth factor (VEGF)-producing cells in human radiation necrosis (RN) are investigated from a histopathological and immunohistochemical standpoint using clinical specimens. Eighteen surgical specimens of symptomatic RN in the brain were retrospectively reviewed. These cases included different original histological tumor types and were treated with different radiation modalities. Histological analyses were performed using hematoxylin and eosin (H&E) staining, and anti-VEGF and anti-hypoxia-inducible factor (HIF)-1α immunohistochemistry. H&E staining showed marked angiogenesis and reactive astrocytosis at the perinecrotic area. The most prominent vasculature in this area was identified as telangiectasis. Immunohistochemistry indicated that HIF-1α was expressed predominantly in the perinecrotic area and that a large majority of VEGF-expressing cells were reactive astrocytes intensively distributed in this area. VEGF produced by the reactive astrocytes localized mainly in the perinecrotic area might be a major cause of both angiogenesis and the subsequent perilesional edema typically found in RN of the brain. The benefits of anti-VEGF antibody (bevacizumab) treatment in RN may be that VEGF secretion from the perinecrotic tissue is inhibited and that surgery would remove this tissue; both of these benefits result in effective reduction of edema associated with RN.

Review of Neurosurgical Fluorescence Imaging Methodologies

Fluorescence imaging in neurosurgery has a long historical development, with several different biomarkers and biochemical agents being used, and several technological approaches. This review focuses on the different contrast agents, summarizing endogenous fluorescence, exogenously stimulated fluorescence and exogenous contrast agents, and then on tools used for imaging. It ends with a summary of key clinical trials that lead to consensus studies. The practical utility of protoporphyrin IX (PpIX) as stimulated by administration of δ-aminolevulinic acid (ALA) has had substantial pilot clinical studies and basic science research completed. Recently multi-center clinical trials using PpIx fluorescence to guide resection have shown efficacy for improved short term survival. Exogenous agents are being developed and tested pre-clinically, and hopefully hold the potential for long term survival benefit if they provide additional capabilities for resection of micro-invasive disease or certain tumor sub-types that do not produce PpIX or help delineate low grade tumors. The range of technologies used for measurement and imaging ranges widely, with most clinical trials being carried out with either point probes or modified surgical microscopes. At this point in time, optimized probe approaches are showing efficacy in clinical trials, and fully commercialized imaging systems are emerging, which will clearly help lead to adoption into neurosurgical practice.

Coregistered fluorescence-enhanced tumor resection of malignant glioma: relationships between δ-aminolevulinic acid-induced protoporphyrin IX fluorescence, magnetic resonance imaging enhancement, and neuropathological parameters. Clinical article

OBJECT

The aim of this study was to investigate the relationships between intraoperative fluorescence, features on MR imaging, and neuropathological parameters in 11 cases of newly diagnosed glioblastoma multiforme (GBM) treated using protoporphyrin IX (PpIX) fluorescence-guided resection.

METHODS

In 11 patients with a newly diagnosed GBM, δ-aminolevulinic acid (ALA) was administered to enhance endogenous synthesis of the fluorophore PpIX. The patients then underwent fluorescence-guided resection, coregistered with conventional neuronavigational image guidance. Biopsy specimens were collected at different times during surgery and assigned a fluorescence level of 0-3 (0, no fluorescence; 1, low fluorescence; 2, moderate fluorescence; or 3, high fluorescence). Contrast enhancement on MR imaging was quantified using two image metrics: 1) Gd-enhanced signal intensity (GdE) on T1-weighted subtraction MR image volumes, and 2) normalized contrast ratios (nCRs) in T1-weighted, postGd-injection MR image volumes for each biopsy specimen, using the biopsy-specific image-space coordinate transformation provided by the navigation system. Subsequently, each GdE and nCR value was grouped into one of two fluorescence categories, defined by its corresponding biopsy specimen fluorescence assessment as negative fluorescence (fluorescence level 0) or positive fluorescence (fluorescence level 1, 2, or 3). A single neuropathologist analyzed the H & E-stained tissue slides of each biopsy specimen and measured three neuropathological parameters: 1) histopathological score (0-IV); 2) tumor burden score (0-III); and 3) necrotic burden score (0-III).

RESULTS

Mixed-model analyses with random effects for individuals show a highly statistically significant difference between fluorescing and nonfluorescing tissue in GdE (mean difference 8.33, p = 0.018) and nCRs (mean difference 5.15, p < 0.001). An analysis of association demonstrated a significant relationship between the levels of intraoperative fluorescence and histopathological score (χ(2) = 58.8, p < 0.001), between fluorescence levels and tumor burden (χ(2) = 42.7, p < 0.001), and between fluorescence levels and necrotic burden (χ(2) = 30.9, p < 0.001). The corresponding Spearman rank correlation coefficients were 0.51 (p < 0.001) for fluorescence and histopathological score, and 0.49 (p < 0.001) for fluorescence and tumor burden, suggesting a strongly positive relationship for each of these variables.

CONCLUSIONS

These results demonstrate a significant relationship between contrast enhancement on preoperative MR imaging and observable intraoperative PpIX fluorescence. The finding that preoperative MR image signatures are predictive of intraoperative PpIX fluorescence is of practical importance for identifying candidates for the procedure. Furthermore, this study provides evidence that a strong relationship exists between tumor aggressiveness and the degree of tissue fluorescence that is observable intraoperatively, and that observable fluorescence has an excellent positive predictive value but a low negative predictive value.

Evaluation of fluoride-labeled boronophenylalanine-PET imaging for the study of radiation effects in patients with glioblastomas

Here we demonstrate that differentiation between glioblastoma (GB) tumor progression (TP) and radiation necrosis (RN) can be achieved with fluoride-labeled boronoalanine positron emission tomography (F-BPA-PET). F-BPA-PET images were obtained from histologically verified 38 GB, 8 complete RN, and 5 RN cases with partial residual tumors. The lesion/normal (L/N) ratios for these groups were 4.2 +/- 1.4, 1.5 +/- 0.3, and 2.0 +/- 0.3, respectively. Ten GB patients underwent F-BPA-PET twice (once before and once after radiation treatment) due to enlargement of the original lesion or the development of new lesions post radiation. The L/N ratios of ten original site lesions had decreased by the second PET, and these lesions were revealed to be RN. In contrast, the L/N ratios of two lesions distant from the original site increased, and these lesions were revealed as cases of TP. Repeat PET imaging was found to be useful for evaluating changes in GB-associated tumor activity with respect to the treatment received.