Combination of FOSCAN® mediated fluorescence guided resection and photodynamic treatment as new therapeutic concept for malignant brain tumors

Cytocidal Effects of Interstitial Photodynamic Therapy Using Talaporfin Sodium and a Semiconductor Laser in a Rat Intracerebral Glioma Model

This preclinical study was conducted to investigate the efficacy of interstitial PDT (i-PDT) for malignant gliomas arising deep within the brain, which are difficult to remove. C6 glioma cells were implanted into the basal ganglia of rats, and 3 weeks later, the second-generation photosensitizer talaporfin sodium (TPS) was administered intraperitoneally. Ninety minutes after administration, a prototype fine plastic optical fiber was punctured into the tumor tissue, and semiconductor laser light was irradiated into the tumor from a 2-mm cylindrical light-emitting source under various conditions. The brain was removed 24 h after the i-PDT and analyzed pathologically. The optical fiber was able to puncture the tumor center in all cases, enabling i-PDT to be performed. Histological analysis showed that tumor necrosis was induced in areas close to the light source, correlating with the irradiation energy dose, whereas apoptosis was induced at some distance from the light source. Irradiation using high energy levels resulted in tissue swelling from strong tumor necrosis, and irradiation at 75 J/cm2 was most suitable for inducing apoptosis. An experimental system of i-PDT using TPS was established using malignant glioma cells transplanted into the rat brain. Tumor cell death, which correlated with the light propagation, was induced in tumor tissue.

Efficacy of interstitial photodynamic therapy using talaporfin sodium and a semiconductor laser for a mouse allograft glioma model

To investigate the therapeutic potential of photodynamic therapy (PDT) for malignant gliomas arising in unresectable sites, we investigated the effect of tumor tissue damage by interstitial PDT (i-PDT) using talaporfin sodium (TPS) in a mouse glioma model in which C6 glioma cells were implanted subcutaneously. A kinetic study of TPS demonstrated that a dose of 10 mg/kg and 90 min after administration was appropriate dose and timing for i-PDT. Performing i-PDT using a small-diameter plastic optical fiber demonstrated that an irradiation energy density of 100 J/cm2 or higher was required to achieve therapeutic effects over the entire tumor tissue. The tissue damage induced apoptosis in the area close to the light source, whereas vascular effects, such as fibrin thrombus formation occurred in the area slightly distant from the light source. Furthermore, when irradiating at the same energy density, irradiation at a lower power density for a longer period of time was more effective than irradiation at a higher power density for a shorter time. When performing i-PDT, it is important to consider the rate of delivery of the irradiation light into the tumor tissue and to set irradiation conditions that achieve an optimal balance between cytotoxic and vascular effects.

Current Photodynamic Therapy for Glioma Treatment: An Update

Research on the development of photodynamic therapy for the treatment of brain tumors has shown promise in the treatment of this highly aggressive form of brain cancer. Analysis of both in vivo studies and clinical studies shows that photodynamic therapy can provide significant benefits, such as an improved median rate of survival. The use of photodynamic therapy is characterized by relatively few side effects, which is a significant advantage compared to conventional treatment methods such as often-used brain tumor surgery, advanced radiotherapy, and classic chemotherapy. Continued research in this area could bring significant advances, influencing future standards of treatment for this difficult and deadly disease.

Photodynamic therapy in brain cancer: mechanisms, clinical and preclinical studies and therapeutic challenges

Cancer is a main cause of death and preferred methods of therapy depend on the type of tumor and its location. Gliomas are the most common primary intracranial tumor, accounting for 81% of malignant brain tumors. Although relatively rare, they cause significant mortality. Traditional methods include surgery, radiotherapy and chemotherapy; they also have significant associated side effects that cause difficulties related to tumor excision and recurrence. Photodynamic therapy has potentially fewer side effects, less toxicity, and is a more selective treatment, and is thus attracting increasing interest as an advanced therapeutic strategy. Photodynamic treatment of malignant glioma is considered to be a promising additional therapeutic option that is currently being extensively investigated in vitro and in vivo. This review describes the application of photodynamic therapy for treatment of brain cancer. The mechanism of photodynamic action is also described in this work as it applies to treatment of brain cancers such as glioblastoma multiforme. The pros and cons of photodynamic therapy for brain cancer are also discussed.

Systematic Review of Photodynamic Therapy in Gliomas

Over the last 20 years, gliomas have made up over 89% of malignant CNS tumor cases in the American population (NIH SEER). Within this, glioblastoma is the most common subtype, comprising 57% of all glioma cases. Being highly aggressive, this deadly disease is known for its high genetic and phenotypic heterogeneity, rendering a complicated disease course. The current standard of care consists of maximally safe tumor resection concurrent with chemoradiotherapy. However, despite advances in technology and therapeutic modalities, rates of disease recurrence are still high and survivability remains low. Given the delicate nature of the tumor location, remaining margins following resection often initiate disease recurrence. Photodynamic therapy (PDT) is a therapeutic modality that, following the administration of a non-toxic photosensitizer, induces tumor-specific anti-cancer effects after localized, wavelength-specific illumination. Its effect against malignant glioma has been studied extensively over the last 30 years, in pre-clinical and clinical trials. Here, we provide a comprehensive review of the three generations of photosensitizers alongside their mechanisms of action, limitations, and future directions.

Unraveling of Functional Activity of Primary Hippocampal Neuron-Glial Networks in Photodynamic Therapy Based on Tetracyanotetra(aryl)porphyrazines

The current efforts in photodynamic therapy (PDT) of brain cancer are focused on the development of novel photosensitizers with improved photodynamic properties, targeted specific localization, and sensitivity to the irradiation dose, ensuring the effectiveness of PDT with fewer side effects for normal nerve tissue. Here, we characterize the effects of four photosensitizers of the tetracyanotetra(aryl)porphyrazine group (pz I–IV) on the functional activity of neuron-glial networks in primary hippocampal cultures in their application in normal conditions and under PDT. The data revealed that the application of pz I–IV leads to a significant decrease in the main parameters of the functional calcium activity of neuron-glial networks and pronounced changes in the network characteristics. The observed negative effects of pz I–IV were aggravated under PDT. Considering the significant restructuring of the functional architectonics of neuron-glial networks that can lead to severe impairments in synaptic transmission and loss of brain functions, and the feasibility of direct application of PDT based on pz I–IV in the therapy of brain tumors is highly controversial. Nevertheless, the unique properties of pz I–IV retain a great prospect of their use in the therapy of tumors of another origin and cellular metabolism.

Targeting glioblastoma stem cells: The first step of photodynamic therapy

Glioblastoma is one of the most malignant types of brain cancer. Evidence suggests that within gliomas there is a small subpopulation of cells with the capacity for self-renewal, called glioma stem cells. These cells could be responsible for tumorigenesis, chemo and radioresistance, and finally for the recurrence of the tumor. Fluorescence-guided resection have improved the results of treatment against this disease, prolonging the survival of patients by a few months. Also, clinical trials have reported potential improvements in the therapeutic response after photodynamic therapy. Thus far, there are few published works that show the response of glioblastoma stem-like cells to photodynamic therapy. Here, we present a brief review exclusively commenting on the therapeutic approaches to eliminate glioblastoma stem cells and on the research publications about this topic of glioblastoma stem cells in relation to photodynamic therapy. It is our hope that this review will be useful to provide an overview about what is known to date on the topic and to promote the generation of new ideas for the eradication of glioblastoma stem cells by photodynamic treatment.

A systematic review and meta-analysis of fluorescent-guided resection and therapy-based photodynamics on the survival of patients with glioma

Glioma is the most common primary central nervous system tumor; many methods are currently being used to research and treat glioma. In recent years, fluorescent-guided resection (FGR) and photodynamic therapy (PDT) have become hot spots in the treatment of glioma. Based on the existing literatures regarding the FGR enhancing resection rate and regarding efficacy of PDT for the treatment of glioma, this paper made a systematic review of FGR for gross total resection of patients and the PDT for the survival of patients with glioma. Meta-analysis of eligible studies was performed to derive precise estimation of PDT on the prognosis of patients with glioma by searching all related literatures in PubMed, EMBASE, Cochrane, and Web of Science databases, and further to evaluate (GTR) under FGR and the efficacy of PDT therapy, including 1-year and 2-year survival rates, overall survival (OS), and progression-free survival (PFS). According to the inclusion and exclusion criteria, a total of 1294 patients with glioma were included in the final analysis of 31 articles, among which a 73.00% (95% CI, 68.00 ~ 79.00%, P < 0.01) rate of GTR in 27 groups included in 23 articles was reported for those receiving FGR. The OS was 17.78 months (95% CI, 8.89 ~ 26.67, P < 0.01) in 5 articles on PDT-treated patients with glioma, and the mean difference of OS was 6.18 (95% CI, 3.3 ~ 9.06, P < 0.01) between PDT treatment and conventional glioma surgery, showing a statistically significant difference (P < 0.01). The PFS was 10.82 months (95% CI, 7.04 ~ 14.61, P < 0.01) in 5 articles on PDT-treated patients with glioma. A 1-year survival rate of 59.00% (95% CI, 38.00 ~ 77.00%, P < 0.01) in 10 groups included in 8 articles and 2-year survival rate of 25.00% (95% CI, 15.00 ~ 36.00%, P < 0.01) in 7 groups included in 6 articles were reported for those with PDT. FGR and PDT are feasible for treatment of patients with glioma, because FGR can effectively increase the resection rate, at the same time, PDT can prolong the survival time. However, due to the limitation of small sample size in the existing studies, larger samples and randomized controlled clinical trials are needed to analyze the resection under FGR and efficacy of PDT in patients with glioma.

Terbium-Based AGuIX-Design Nanoparticle to Mediate X-ray-Induced Photodynamic Therapy

X-ray-induced photodynamic therapy is based on the energy transfer from a nanoscintillator to a photosensitizer molecule, whose activation leads to singlet oxygen and radical species generation, triggering cancer cells to cell death. Herein, we synthesized ultra-small nanoparticle chelated with Terbium (Tb) as a nanoscintillator and 5-(4-carboxyphenyl succinimide ester)-10,15,20-triphenyl porphyrin (P1) as a photosensitizer (AGuIX@Tb-P1). The synthesis was based on the AGuIX@ platform design. AGuIX@Tb-P1 was characterised for its photo-physical and physico-chemical properties. The effect of the nanoparticles was studied using human glioblastoma U-251 MG cells and was compared to treatment with AGuIX@ nanoparticles doped with Gadolinium (Gd) and P1 (AGuIX@Gd-P1). We demonstrated that the AGuIX@Tb-P1 design was consistent with X-ray photon energy transfer from Terbium to P1. Both nanoparticles had similar dark cytotoxicity and they were absorbed in a similar rate within the cells. Pre-treated cells exposure to X-rays was related to reactive species production. Using clonogenic assays, establishment of survival curves allowed discrimination of the impact of radiation treatment from X-ray-induced photodynamic effect. We showed that cell growth arrest was increased (35%-increase) when cells were treated with AGuIX@Tb-P1 compared to the nanoparticle doped with Gd.

Using Light for Therapy of Glioblastoma Multiforme (GBM)

: Glioblastoma multiforme (GBM) is the most malignant form of primary brain tumour with extremely poor prognosis. The current standard of care for newly diagnosed GBM includes maximal surgical resection followed by radiotherapy and adjuvant chemotherapy. The introduction of this protocol has improved overall survival, however recurrence is essentially inevitable. The key reason for that is that the surgical treatment fails to eradicate GBM cells completely, and adjacent parenchyma remains infiltrated by scattered GBM cells which become the source of recurrence. This stimulates interest to any supplementary methods which could help to destroy residual GBM cells and fight the infiltration. Photodynamic therapy (PDT) relies on photo-toxic effects induced by specific molecules (photosensitisers) upon absorption of photons from a light source. Such toxic effects are not specific to a particular molecular fingerprint of GBM, but rather depend on selective accumulation of the photosensitiser inside tumour cells or, perhaps their greater sensitivity to the effects, triggered by light. This gives hope that it might be possible to preferentially damage infiltrating GBM cells within the areas which cannot be surgically removed and further improve the chances of survival if an efficient photosensitiser and hardware for light delivery into the brain tissue are developed. So far, clinical trials with PDT were performed with one specific type of photosensitiser, protoporphyrin IX, which tends to accumulate in the cytoplasm of the GBM cells. In this review we discuss the idea that other types of molecules which build up in mitochondria could be explored as photosensitisers and used for PDT of these aggressive brain tumours.

Photodynamic Therapy for the Treatment of Glioblastoma

Glioblastoma is the most common form of adult brain cancer and remains one of the deadliest of human cancers. The current standard-of-care involves maximal tumor resection followed by treatment with concurrent radiation therapy and the chemotherapy temozolomide. Recurrence after this therapy is nearly universal within 2 years of diagnosis. Notably, >80% of recurrence is found in the region adjacent to the resection cavity. The need for improved local control in this region, thus remains unmet. The FDA approval of 5-aminolevulinic acid (5-ALA) for fluorescence guided glioblastoma resection renewed interests in leveraging this agent as a means to administer photodynamic therapy (PDT). Here we review the general principles of PDT as well as the available literature on PDT as a glioblastoma therapeutic platform.

Application of photodynamic therapy drugs for management of glioma

Human gliomas are one of the most prevalent and challenging-to-treat adult brain tumors, and thus result in high morbidity and mortality rates worldwide. Current research and treatments of gliomas include surgery associated with conventional chemotherapy, use of biologicals, radiotherapy, and medical device applications. The selected treatment options are often guided by the category and aggressiveness of this deadly disease and the patient’s conditions. However, the effectiveness of these approaches is still limited due to poor drug efficacy (including delivery to desired sites), undesirable side effects, and high costs associated with therapies. In addition, the degree of leakiness of the blood–brain barrier (BBB) that regulates trafficking of molecules in and out of the brain also modulates accumulation of adequate drug levels to tumor sites. Active research is being pursued to overcome these limitations to obtain a superior therapeutic index and enhanced patient survival. One area of development in this direction focuses on the localized application of photodynamic therapy (PDT) drugs to cure brain cancers. PDT molecules potentially utilize multiple pathways based on their ability to generate reactive oxygen species (ROS) upon photoactivation by a suitable light source. In this communication, we have attempted to provide a brief overview of PDT and cancer, photoactivation pathways, mechanism of tumor destruction, effect of PDT on tumor cell viability, immune activation, various research attempted by applying PDT in combination with novel strategies to treat glioma, role of BBB and clinical status of PDT therapy for glioma treatment.

Liposomal Lapatinib in Combination with Low-Dose Photodynamic Therapy for the Treatment of Glioma

BACKGROUND

Malignant gliomas are highly invasive and extremely difficult to treat tumours with poor prognosis and outcomes. Photodynamic therapy (PDT), mediated by Gleolan®, has been studied previously with partial success in treating these tumours and extending lifetime. We aim to determine whether combining PDT using ALA-protoporphyrin IX (PpIX) with a liposomal formulation of the clinical epidermal growth factor receptor (EGFR) inhibitor, lapatinib, would increase the anti-tumour PDT efficacy.

METHODS

Lapatinib was given in vitro and in vivo 24 h prior to PDT and for 3-5 days following PDT to elicit whether the combination provided any benefits to PDT therapy. Live-cell imaging, in vitro PDT, and in vivo studies were performed to elucidate the effect lapatinib had on PDT for a variety of glioma cell lines and as well as GSC-30 neurospheres in vivo.

RESULTS

PDT combined with lapatinib led to a significant increase in PpIX accumulation, and reductions in the LD₅₀ of PpIX mediated PDT in two EGFR-driven cell lines, U87 and U87vIII, tested (p < 0.05). PDT + lapatinib elicited stronger MRI-quantified glioma responses following PDT for two human glioma-derived tumours (U87 and GSC-30) in vivo (p < 0.05). Furthermore, PDT leads to enhanced survival in rats following treatment with lapatinib compared to lapatinib alone and PDT alone (p < 0.05).

CONCLUSIONS

As lapatinib is approved for other oncological indications, a realization of its potential combination with PDT and in fluorescence-guided resection could be readily tested clinically. Furthermore, as its use would only be in acute settings, long-term resistance should not pose an issue as compared to its use as monotherapy.

Seeing Better and Going Deeper in Cancer Nanotheranostics

Biomedical imaging modalities in clinical practice have revolutionized oncology for several decades. State-of-the-art biomedical techniques allow visualizing both normal physiological and pathological architectures of the human body. The use of nanoparticles (NP) as contrast agents enabled visualization of refined contrast images with superior resolution, which assists clinicians in more accurate diagnoses and in planning appropriate therapy. These desirable features are due to the ability of NPs to carry high payloads (contrast agents or drugs), increased in vivo half-life, and disease-specific accumulation. We review the various NP-based interventions for treatments of deep-seated tumors, involving "seeing better" to precisely visualize early diagnosis and "going deeper" to activate selective therapeutics in situ.

THE ROLE OF PHOTODYNAMIC THERAPY IN THE TREATMENT OF PRIMARY, RECURRENT AND METASTATIC MALIGNANT BRAIN TUMORS

Photodynamic therapy is a relevant and promising area for research in the field of clinical neuroonocology. Application of modern developments in the field of laser technologies and new photosensitizers allows us to refer to this field as to high-tech. According to various authors, the inclusion of photodynamic therapy in combined and complex treatments of patients with malignant brain tumors allows achieving overall survival median of patients from 11 to 26 months for primary form of glioblastoma, and from 7.5 to 15 months - for recurrent forms of glioblastoma. Certain results have been achieved in the treatment of patients with metastatic brain lesion. In this publication the authors analyzed and systematized the results of the main clinical studies in the field of fluorescent diagnostics and intraoperative photodynamic therapy of primary, recurrent and metastatic forms of malignant brain tumors.

Oncologic Photodynamic Therapy: Basic Principles, Current Clinical Status and Future Directions

Photodynamic therapy (PDT) is a clinically approved cancer therapy, based on a photochemical reaction between a light activatable molecule or photosensitizer, light, and molecular oxygen. When these three harmless components are present together, reactive oxygen species are formed. These can directly damage cells and/or vasculature, and induce inflammatory and immune responses. PDT is a two-stage procedure, which starts with photosensitizer administration followed by a locally directed light exposure, with the aim of confined tumor destruction. Since its regulatory approval, over 30 years ago, PDT has been the subject of numerous studies and has proven to be an effective form of cancer therapy. This review provides an overview of the clinical trials conducted over the last 10 years, illustrating how PDT is applied in the clinic today. Furthermore, examples from ongoing clinical trials and the most recent preclinical studies are presented, to show the directions, in which PDT is headed, in the near and distant future. Despite the clinical success reported, PDT is still currently underutilized in the clinic. We also discuss the factors that hamper the exploration of this effective therapy and what should be changed to render it a more effective and more widely available option for patients.

Photodynamic Therapy for Malignant Brain Tumors

Photodynamic therapy (PDT) using talaporfin sodium together with a semiconductor laser was approved in Japan in October 2003 as a less invasive therapy for early-stage lung cancer. The author believes that the principle of PDT would be applicable for controlling the invading front of malignant brain tumors and verified its efficacy through experiments using glioma cell lines and glioma xenograft models. An investigator-initiated clinical study was jointly conducted with Tokyo Women’s Medical University with the support of the Japan Medical Association. Patient enrollment was started in May 2009 and a total of 27 patients were enrolled by March 2012. Of 22 patients included in efficacy analysis, 13 patients with newly diagnosed glioblastoma showed progression-free survival of 12 months, progression-free survival at the site of laser irradiation of 20 months, 1-year survival of 100%, and overall survival of 24.8 months. In addition, the safety analysis of the 27 patients showed that adverse events directly related to PDT were mild. PDT was approved in Japan for health insurance coverage as a new intraoperative therapy with the indication for malignant brain tumors in September 2013. Currently, the post-marketing investigation in the accumulated patients has been conducted, and the preparation of guidelines, holding training courses, and dissemination of information on the safe implementation of PDT using web sites and videos, have been promoted. PDT is expected to be a breakthrough for the treatment of malignant glioma as a tumor cell-selective less invasive therapy for the infiltrated functional brain area.

Photodynamic therapy (PDT) for malignant brain tumors--where do we stand?

INTRODUCTION

What is the current status of photodynamic therapy (PDT) with regard to treating malignant brain tumors? Despite several decades of effort, PDT has yet to achieve standard of care.

PURPOSE

The questions we wish to answer are: where are we clinically with PDT, why is it not standard of care, and what is being done in clinical trials to get us there.

METHOD

Rather than a meta-analysis or comprehensive review, our review focuses on who the major research groups are, what their approaches to the problem are, and how their results compare to standard of care. Secondary questions include what the effective depth of light penetration is, and how deep can we expect to kill tumor cells.

CURRENT RESULTS

A measurable degree of necrosis is seen to a depth of about 5mm. Cavitary PDT with hematoporphyrin derivative (HpD) results are encouraging, but need an adequate Phase III trial. Talaporfin with cavitary light application appears promising, although only a small case series has been reported. Foscan for fluorescence guided resection (FGR) plus intraoperative cavitary PDT results were improved over controls, but are poor compared to other groups. 5-Aminolevulinic acid-FGR plus postop cavitary HpD PDT show improvement over controls, but the comparison to standard of care is still poor.

CONCLUSION

Continued research in PDT will determine whether the advances shown will mitigate morbidity and mortality, but certainly the potential for this modality to revolutionize the treatment of brain tumors remains. The various uses for PDT in clinical practice should be pursued.

Intra-operative acidosis during 5-aminolevulinic acid assisted glioma resection

A 47-year-old man underwent 5-aminolevulinic acid assisted resection of high grade glioma. Intraoperatively, he developed a compensated lactic acidosis that was managed medically and did not cause long term complications.

Multifunctional biodegradable polyacrylamide nanocarriers for cancer theranostics--a "see and treat" strategy

We describe here the development of multifunctional nanocarriers, based on amine-functionalized biodegradable polyacrylamide nanoparticles (NPs), for cancer theranostics, including active tumor targeting, fluorescence imaging, and photodynamic therapy. The structural design involves adding primary amino groups and biodegradable cross-linkers during the NP polymerization, while incorporating photodynamic and fluorescent imaging agents into the NP matrix, and conjugating PEG and tumor-targeting ligands onto the surface of the NPs. The as-synthesized NPs are spherical, with an average diameter of 44 nm. An accelerated biodegradation study, using sodium hydroxide or porcine liver esterase, indicated a hydrogel polymer matrix chain collapse within several days. By using gel permeation chromatography, small molecules were detected, after the degradation. In vitro targeting studies on human breast cancer cells indicate that the targeted NPs can be transported efficiently into tumor cells. Incubating the multifunctional nanocarriers into cancer cells enabled strong fluorescence imaging. Irradiation of the photosensitizing drug, incorporated within the NPs, with light of a suitable wavelength, causes significant but selective damage to the impregnated tumor cells, but only inside the illuminated areas. Overall, the potential of polymeric-based NPs as biodegradable, multifunctional nanocarriers, for cancer theranostics, is demonstrated here.

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.

Temoporfin (Foscan®, 5,10,15,20-tetra(m-hydroxyphenyl)chlorin)--a second-generation photosensitizer

This review traces the development and study of the second-generation photosensitizer 5,10,15,20-tetra(m-hydroxyphenyl)chlorin through to its acceptance and clinical use in modern photodynamic (cancer) therapy. The literature has been covered up to early 2011.

Management of recurrent malignant glioma--neurosurgical strategies

There is currently no standard for neurosurgical interventions in patients with recurrent high grade gliomas. An individualized approach is recommended as well for decision-making as for planning an intervention with resection of the outmost possible amount of tumor tissue while preserving neurological function and thus quality of life. Recent technical developments of imaging and of neuronavigation and visualization of tumor tissue with in vivo fluorescence with 5-Ala have proved helpful in improving symptoms and prolonging survival times also for patients with recurrent malignant gliomas.

Site-specific opening of the blood-brain barrier

The blood-brain barrier (BBB) poses a significant impediment for the delivery of therapeutic drugs into the brain. This is particularly problematic for the treatment of malignant gliomas which are characterized by diffuse infiltration of tumor cells into normal brain where they are protected by a patent BBB. Selective disruption of the BBB, followed by administration of anti-cancer agents, represents a promising approach for the elimination of infiltrating glioma cells. A summary of the techniques (focused ultrasound, photodynamic therapy and photochemical internalization) for site-specific opening of the BBB will be discussed in this review. Each approach is capable of causing localized and transient opening of the BBB with minimal damage to surrounding normal brain as evidenced from magnetic resonance images and histology.

Photodynamic applications in brain tumors: a comprehensive review of the literature

INTRODUCTION

GBM is the comment glioma. GBM-outcome had not changed much over two decades despite leaps in medical technology. Fewer than 25% survive 2 years. There is no jacket that fits all GBMs. This paper reviews the evidence for PDT in GBMs.

RATIONALE

Maximum safe resection is supported by level-II evidence. PDT-technology (PDTT) provides means to maximize safe resection. PDTT paints GBM red in contrast to brain because of selective uptake and retention of photosensitizers. Exposure to specific light wave produces cytotoxic singlet oxygen. PDT-APPLICATIONS: (1) Fluorescence image guided biopsy to sample high grade components of what looks like low grade glioma on MRI, 89% sensitive. (2) Fluorescence image guided surgery for maximum safe surgical resection is >84% sensitive, achieves complete resection in >65% and prolongs tumor free survival (1 observational and 2 RCT, p < 0.001). (3) Photodynamic treatment supported by several observational studies with combined total of >1000 patients and 3 RCT used PDT in GBMs. PDT was highly selective, safe, significantly improved good quality survival, and delayed tumor relapse (p < 0.001).

SAFETY

PDT had a very high safety track record, thromboembolism 2%, brain-oedema 1.3%, and skin photosensitivity complications 1-3%.

CONCLUSION

PDT in GBMs is safe, selective, and sensitive and leads to significant prolongation of good quality survival, delay in tumor relapse and significant reduction of further interventions. It would be impractical, impossible and probably unethical to randomize patients between PDT and placebo, in the same way it would be unethical to carry out a RCT to prove that the parachute saves lives.

Photodynamic diagnosis and therapy and the brain

Photodynamic techniques such as photodynamic diagnosis (PDD), fluorescence-guided tumour resection (FGR) and photodynamic therapy (PDT) are currently undergoing intensive clinical investigations as adjuvant treatment for malignant brain tumours. The following chapter provides an overview on the current clinical data and trials of PDT as well as photosensitizers, technical developments and indications for photodynamic application in neurosurgery. Besides many clinical phase I/II trials for PDT for malignant brain tumours, there are only few controlled clinical trials following tumour resection. Variations in treatment protocols, variation of photosensitizers and light dose make the evaluation scientifically difficult; however there is a clear trend towards prolonging median survival after one single photodynamic treatment as compared to standard therapeutic regimens. According to the meta analysis the median survival after PDT for primary glioblastoma multiforme (WHO grade IV) was 22 months and for recurrent GBM was 9 months as compared to standard conventional treatment, in which it is 15 and 3 months, respectively. Fluorescence-guided resection of the tumour demonstrated significant greater reduction of tumour burden. The combination of PDD/ FGR and intraoperative PDT ("to see and to treat") offers an exciting approach to the treatment of malignant brain tumours. PDT was generally well tolerated and side effects consisted of occasionally increased intracranial pressure and prolonged skin sensitivity against direct sunlight.