New light on the brain: The role of photosensitizing agents and laser light in the management of invasive intracranial tumors

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.

[Clinical guidelines for the use of intraoperative fluorescence diagnosis in brain tumor surgery]

In this paper, we present a review of current literature on the application of intraoperative fluorescence diagnosis and fluorescence spectroscopy using 5-aminolevulinic acid in surgery for various types of brain tumors, both alone and in combination with other neuroimaging methods. Authors' extensive experience with these methods allowed them to develop a set of clinical guidelines for the use of intraoperative fluorescence diagnosis and fluorescence spectroscopy in surgery of brain tumors.

Photodynamic assisted surgical resection and treatment of malignant brain tumours technique, technology and clinical application

Malignant brain tumours have a dismal prognosis with current state of the art technology. The main reasons for this lost battle in the battlefield of cancer are tumour cell invisibility to the surgical microscope and brain invasion. However, the vast majority of these tumours relapse locally making local radical removal the main strategy in their successful eradication. PDD and PDT combined with new technology stands a very good chance of achieving this goal by maximising tumour resection (PDD) and selective tumour kill (PDT). The aim of this paper is to explain how this is done at Ninewells Hospital and Medical School, Dundee, Scotland. The technique and technology described in this paper, provide a means of diffusing the light to the periphery of the tumour cavity with subsequent therapeutic sessions and treatment dose escalation at the bedside, saving time and resources.

Photofrin based photodynamic therapy and miR-99a transfection inhibited FGFR3 and PI3K/Akt signaling mechanisms to control growth of human glioblastoma In vitro and in vivo

Glioblastoma is the most common malignant brain tumor in humans. We explored the molecular mechanisms how the efficacy of photofrin based photodynamic therapy (PDT) was enhanced by miR-99a transfection in human glioblastoma cells. Our results showed almost similar uptake of photofrin after 24 h in different glioblastoma cells, but p53 wild-type cells were more sensitive to radiation and photofrin doses than p53 mutant cells. Photofrin based PDT induced apoptosis, inhibited cell invasion, prevented angiogenic network formation, and promoted DNA fragmentation and laddering in U87MG and U118MG cells harvoring p53 wild-type. Western blotting showed that photofrin based PDT was efficient to block the angiogenesis and cell survival pathways. Further, photofrin based PDT followed by miR-99a transfection dramatically increased miR-99a expression and also increased apoptosis in glioblastoma cell cultures and drastically reduced tumor growth in athymic nude mice, due to down regulation of fibroblast growth factor receptor 3 (FGFR3) and PI3K/Akt signaling mechanisms leading to inhibition of cell proliferation and induction of molecular mechanisms of apoptosis. Therefore, our results indicated that the anti-tumor effects of photofrin based PDT was strongly augmented by miR-99a overexpression and this novel combination therapeutic strategy could be used for controlling growth of human p53 wild-type glioblastomas both in vitro and in vivo.

Investigational therapies for brain metastases

Contrary to the incidence of primary cancers, the incidence of brain metastasis has been increasing. This increase is likely because of the effects of an aging population, improved neuroimaging surveillance, and better control of systemic cancer, allowing time for brain metastasis to occur. Unlike systemic cancers, for which chemotherapy is the mainstay of treatment, the therapeutic strategies available to treat brain metastasis have traditionally been limited to surgical resection, whole brain radiation therapy, or stereotactic radiosurgery, either individually or in combination. It is important to put the treatment in the context of the prognosis for patients with brain metastases.

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.

Intraoperative optical identification of pituitary adenomas

INTRODUCTION

The main goals of transsphenoidal pituitary surgery are total removal of pituitary adenomas (PAs) and preservation of normal pituitary functions. Achieving these goals is dependent upon the precise localisation of PAs during surgery, particularly secreting microadenomas. However, some microadenomas are invisible on preoperative imaging and during surgery, leading some surgeons to perform total hypophysectomy in many patients to achieve cure at the expense of panhypopituitrism. We have examined optical detection systems to identify PAs intraoperatively. This paper reports our preliminary findings.

METHODS

A prospective observational study design.

TECHNIQUE

Patients were given 20 mg/kg body weight 5-aminolevulinic acid (ALA) mixed in 30 ml of orange juice, orally 3 h before surgery. Surgery was performed in the supine position, under image guidance, through the right nostril using Storz 0 degree endoscope assisted with microsurgery as required. The endoscope was attached to photodiagnostic filters (PD) allowing switching the light from white to blue at the flick of a foot pedal. After the dura of the floor of the sella was incised a laser probe was inserted into the pituitary gland to identify the ALA-induced protoporphyrin IX spectroscopy at 632 nm, using an optical biopsy system (OBS). Once the adenoma was identified by the OBS it was exposed and examined by the PD system to detect fluorescence. The PA was removed and its type was confirmed by histopathology and correlated to the OBS and PD system findings.

PATIENTS

Thirty consecutive patients were studied: 14 were non-functioning macroadenomas (NFA), 12 were secreting PAs and 4 pituitary cysts. The secreting PAs were GH (2), ACTH (3), prolactin (2) and gonadotrophins (5). Six were microadenomas (3 ACTH, 1 GH, 2 prolactin) and 20 were macroadenomas, of which 12 were invading macroadenomas. Twenty-four of these were examined by the OBS and the PD systems and six were examined by the PD system only. The true positive (sensitivity) of the PD and OBS systems were 80.8% (21/26) and 95.5% (21/22) respectively. The true negative (specificity) of PD and OBS were 75% (3/4) and 100% (2/2) respectively. The false negative rate of PD was 19.2% (5/26) and for OBS was 4.5% (1/22), while the false positive rate for PD was 25% (1/4) and for OBS was 0.

CONCLUSION

Intraoperative optical identification of pituitary adenomas is a feasible and reliable way to localize pituitary adenomas during transsphenoidal surgery and it may lead to improved cure rate and preservation of normal pituitary functions.

Photodynamic therapy for treatment of solid tumors--potential and technical challenges

Photodynamic therapy (PDT) involves the administration of photosensitizer followed by local illumination with visible light of specific wavelength(s). In the presence of oxygen molecules, the light illumination of photosensitizer can lead to a series of photochemical reactions and consequently the generation of cytotoxic species. The quantity and location of PDT-induced cytotoxic species determine the nature and consequence of PDT. Much progress has been seen in both basic research and clinical application in recent years. Although the majority of approved PDT clinical protocols have primarily been used for the treatment of superficial lesions of both malignant and non-malignant diseases, interstitial PDT for the ablation of deep-seated solid tumors are now being investigated worldwide. The complexity of the geometry and non-homogeneity of solid tumor pose a great challenge on the implementation of minimally invasive interstitial PDT and the estimation of PDT dosimetry. This review will discuss the recent progress and technical challenges of various forms of interstitial PDT for the treatment of parenchymal and/or stromal tissues of solid tumors.

Intratumoral vs systemic administration of meta-tetrahydroxyphenylchlorin for photodynamic therapy of malignant gliomas: assessment of uptake and spatial distribution in C6 rat glioma model

Malignant gliomas, with an incidence of 5 cases per 100,000 population per year, represent the most common primary brain tumour. They have an overall survival length of less than 2 years. Many different adjuvant therapies have been developed. Among them, Photodynamic Therapy (PDT), that is based on photochemical reactions between light and tumoral tissue selectively labelled with exogenous photosensitizing agents. Among photosensitizers, m-THPC (Temoporfin), seems to be the most promising one for the treatment of brain tumors, but, unfortunately, it causes problems of high skin photosensitivity. To by-pass this problem, we devised an intratumoral route of administration of this photosensitizer. The aim of this study is to investigate and compare the uptake of m-THPC in brain tumor and normal tissue after systemic and intratumoral administration of the drug. 30 female Wistar rats received m-THPC 12 days after C6 tumor implantation. Temoporfin was administered intratumorally in 24 rats at two different concentrations. 6 rats constituted the control group and received m-THPC by means of an intraperitoneal injection. The brains were extracted at 4 h, 24 h and 96 h after Temoporfin injection. The samples were examined with a confocal laser scanning microscope. All samples showed high fluorescence emission exclusively in the tumour area, without appreciable differences between the samples taken at the different times of sacrifice and the two routes of administration. No fluorescence whatsoever was detected among normal brain tissue surrounding the tumour. The intratumoral route appears to give comparable results to the systemic one, regarding intracellular uptake efficiency and tumour--normal tissue ratio, with the advantage of a much shorter time needed to reach optimal intratumoural concentration--that is just four hours from m-THPC injection.

ALA and Photofrin fluorescence-guided resection and repetitive PDT in glioblastoma multiforme: a single centre Phase III randomised controlled trial

Glioblastoma multiforme (GBM) carries dismal prognosis and cannot be eradicated surgically because of its wide brain invasion. The objective of this prospective randomised controlled trial was to evaluate ALA and Photofrin fluorescence-guided resection (FGR) and repetitive photodynamic therapy (PDT) in GBM. We recruited 27 patients; 13 were in the study group and 14 were in the control group. The mean survival of the study group was 52.8 weeks compared to 24.6 weeks in the control group (p<0.01). The study group gained on average 20 points on the Karnofsky performance score (p<0.05). There were no differences in complications or hospital stay between the two groups. The mean time to tumour progression was 8.6 months in the study group compared to 4.8 months in the control group (p<0.05). Therefore, ALA and Photofrin fluorescence-guided resection and repetitive PDT offered a worthwhile survival advantage without added risk to patients with GBM. A multicentre randomized controlled trial is warranted to confirm these results.

Immunonanoshells for targeted photothermal ablation in medulloblastoma and glioma: an in vitro evaluation using human cell lines

We are developing a novel approach to specifically target malignant brain tumor cells for photothermal ablation using antibody-tagged, near infrared-absorbing gold-silica nanoshells, referred to as immunonanoshells. Once localized to tumor cells, these nanoshells are extremely efficient at absorbing near-infrared light and can generate sufficient heat to kill cancer cells upon exposure to laser light. In this study, we evaluated the efficacy of immunonanoshells in vitro against both medulloblastoma and high-grade glioma cell lines. We used an antibody against HER2 to target gold-silica nanoshells to medulloblastoma cells, since HER2 is frequently overexpressed in medulloblastoma. We show that treatment with HER2-targeted nanoshells, but not non-targeted nanoshells, followed by exposure to laser light, can induce cell death in the HER2-overexpressing medulloblastoma cell line Daoy.2, as well as the parental Daoy cell line, which expresses HER2 at a moderate level, but not in dermal fibroblasts that do not express HER2. In an analogous set of experiments, we conjugated gold-silica nanoshells to an antibody against interleukin-13 receptor-alpha 2 (IL13Ralpha2), an antigen that is frequently overexpressed in gliomas. We demonstrate that these immunonanoshells are capable of inducing cell death in two high-grade glioma cell lines that express IL13Ralpha2, U373 and U87, but not in A431 epidermoid carcinoma cells that do not express significant levels of IL13Ralpha2. We believe that the use of antibody-tagged gold-silica nanoshells to selectively target cancer cells presents a promising new strategy for the treatment of central nervous system tumors that will minimize the damage and resulting toxicity to the surrounding normal brain.

Singlet oxygen quantum yields of potential porphyrin-based photosensitisers for photodynamic therapy

The singlet oxygen formation quantum yield (Phi(Delta)) for solutions of the di-cation, free-base and metallated forms of hematoporphyrin derivative (HpD), hematoporphyrin IX (Hp9) and a boronated protoporphyrin (BOPP) are reported using the method of direct detection of the characteristic phosphorescence following polychromatic excitation. Values of Phi(Delta) for the free-base form of all the porphyrins and the di-cation forms of Hp9 and HpD are in the range of 0.44 to 0.85 in the solvents investigated. Incorporation of zinc ions into the macrocycle reduces Phi(Delta) for all three porphyrins. BOPP facilitates the coordination of certain transition metals (Mn, Co and Cu) compared to Hp9 and HpD and results in a dramatic decrease in Phi(Delta). The experimental data suggest the introduction of low energy charge transfer states associated with the disruption of the planarity of the macrocyclic ring provides alternative non-radiative deactivation pathways. In BOPP, this non-planarity is augmented by the large closo-carborane peripheral substituent groups.

Photodynamic therapy of cerebral glioma – A review Part II – Clinical studies

Photodynamic therapy (PDT) is a binary treatment modality that has been used to treat malignant brain tumours for 25 years. The treatment involves the selective uptake of a photosensitizer (PS) by the tumour cells followed by irradiation of the tumour with light of the appropriate wavelength to excite and activate the PS resulting in selective tumour destruction and is a potentially valuable adjunct to surgical excision and other conventional therapies. PDT has undergone extensive laboratory studies and clinical trials with a variety of PS and tumour models. These are discussed with reference mainly to clinical studies involving the PDT of brain tumours.

PDT-induced death of sensory neurons and glial cells in the isolated crayfish stretch receptor after proteolytic treatment

To study the involvement of neuroglial interactions in photodynamic damage of crayfish stretch receptor, which consists of only two neurons surrounded by satellite glial cells (SGCs), we attempted to proteolytically uncouple neurons and glia and then compare the responses of these cells to photosensitization when intercellular communications were intact or impaired. After incubation of isolated stretch receptors with pronase or collagenase they were photosensitized with Photosens, a mixture of sulfonated alumophthalocyanines AlPcS(n) (n = 2, 3, and 4; mean n = 3.1). In the next 6 hr the preparations were double fluorochromed with propidium iodide and Hoechst-33342 to visualize necrotic and apoptotic cells. Proteolytic treatment shortened bioelectric neuron response and precipitated its functional inactivation; however, it did not significantly impair neuron morphology and did not induce its necrosis either in the darkness or under photosensitization. Photodynamic treatment induced necrosis of neurons and SGC and apoptosis of glial cells. Pronase but not collagenase increased percent of necrotic and apoptotic SGCs in the darkness and thus reduced the number of glial cells around the neuron; however, both pronase and collagenase prevented photodynamically induced apoptosis of glial cells. The involvement of neuron-to-glia signaling interactions in this phenomenon is suggested.

New Delivery Approaches for Pediatric Brain Tumors

For many types of childhood brain tumors, including malignant gliomas, disease progression at the primary site is the predominant mode of treatment failure. Accordingly, interest has been directed during the last decade on exploring strategies to enhance the delivery of therapeutically active agents into the tumor microenvironment. Two approaches that have been the focus of considerable attention in the treatment of adult malignant brain tumors include interstitial administration of chemotherapeutic agents using time-release polymers and convection-enhanced delivery of immunotoxin conjugates targeted to receptors overexpressed in brain tumors relative to normal brain cells. Although it remains to be determined whether these approaches will lead to meaningful improvements in disease control and long-term prognosis in children with brain tumors, the encouraging results from studies in adults support the rationale for further exploring these strategies in the pediatric setting.

Mild skin photosensitivity in cancer patients following injection of Photochlor (2-[1-hexyloxyethyl]-2-devinyl pyropheophorbide-a; HPPH) for photodynamic therapy

PURPOSE

To measure skin photosensitivity in cancer patients infused with the new second-generation photodynamic sensitizer Photochlor (2-[1-hexyloxyethyl]-2-devinyl pyropheophorbide-a). A major disadvantage of using the clinically approved photosensitizer Photofrin is potentially prolonged and sometimes severe cutaneous phototoxicity.

PATIENTS AND METHODS

Forty-eight patients enrolled in Phases 1 and 2 clinical trials underwent two or more exposures to four graded doses (44.4, 66.6, 88.8 or 133.2 J/cm2) of artificial solar-spectrum light (SSL) before and after administration of Photochlor at a dose of 2.5, 3, 4, 5 or 6 mg/m2 .

RESULTS

The most severe skin response, experienced by only six of the subjects, was limited to erythema without edema and could only be elicited by exposure to the highest light dose. Conversely, eight subjects had no discernible reaction to SSL at any light dose. For nearly all the patients, the peak skin response was obtained when the interval between sensitizer injection and exposure to SSL was 1 day and, generally, their sensitivity to SSL decreased with increasing sensitizer-light interval. For example, a 2-day sensitizer-SSL interval resulted in less severe reactions than those obtained with the 1-day interval in 79% of the subjects, while 90% of the subjects exposed to SSL 3 days after Photochlor infusion had responses that were less severe than those obtained with either the 1- or 2-day sensitizer-SSL interval.

CONCLUSIONS

Photochlor, at clinically effective antitumor doses, causes only mild skin photosensitivity that declines rapidly over a few days.

A review of progress in clinical photodynamic therapy

Photodynamic therapy (PDT) has received increased attention since the regulatory approvals have been granted to several photosensitizing drugs and light applicators worldwide. Much progress has been seen in basic sciences and clinical photodynamics in recent years. This review will focus on new developments of clinical investigation and discuss the usefulness of various forms of PDT techniques for curative or palliative treatment of malignant and non-malignant diseases.