Photoradiation therapy and its potential in the management of neurological tumors

Effect of structural variation on tumor targeting efficacy of cationically charged porphyrin derivatives: Comparative in-vitro and in-vivo evaluation for possible potential in PET and PDT

tetracationic (TMPyP) and tricationic porphyrin (TriMPyCOOHP) derivatives were synthesized, characterized and investigated for binding with DNA by Isothermal Titration Calorimetry as well as by UV-Vis spectroscopy in order to study the effect of structural variation on tumor targeting efficacy of cationically charged porphyrin derivatives. Fluorescence cell imaging studies performed in cancer cell lines corroborated the findings of aforementioned studies. Photocytotoxicity experiments in A549 cell lines revealed relatively higher light dependent cytotoxic effects exerted by TMPyP compared to TriMPyCOOHP. In-vivo experiments in tumor bearing animal model revealed relatively longer retention of ⁶⁸Ga-TMPyP in tumorous lesion compared to that of ⁶⁸Ga-TriMPyCOOHP. The study reveals that removal of one of the positive charges of the tetracationic porphyrin derivatives significantly reduces their DNA binding ability and cytotoxicity as well as brings changes in the pharmacokinetic pattern and tumor retention in small animal model.

Intraoperative Photodiagnosis for Malignant Glioma Using Photosensitizer Talaporfin Sodium

Objective: The aim of this study was to demonstrate the clinical feasibility of intraoperative photodiagnosis (PD) of malignant brain tumor using talaporfin sodium (TPS), which is an agent used in photodynamic therapy (PDT) for cancers. Methods: Forty-seven patients diagnosed with malignant gliomas by preoperative imaging (42 patients with gliomas and 5 patients with other brain tumors) received an intravenous injection of TPS at 40 mg/m² 24 h before resection. During surgery, these patients were irradiated with diode laser light at 664 nm, and tumor fluorescence was observed. The fluorescence intensity was visually rated on a 3-point rating scale [strong fluorescence, weak fluorescence and no fluorescence]. TPS concentrations in 124 samples from 47 cases were measured by HPLC (High performance liquid chromatography). Results: The fluorescence intensity was confirmed to be weak in all patients with Grade II gliomas and strong in almost all patients with Grade III or IV gliomas, reflecting the histological grade of malignancy. In patients with non-glioma brain tumors except for 1 patient with a metastatic brain tumor, the fluorescence intensity was strong. The mean TPS concentration in tissues was 1.62 μg/g for strong fluorescence areas, 0.67 μg/g for weak fluorescence areas and 0.19 μg/g for no fluorescence areas. Conclusions: Establishment of an appropriate fluorescence observation system enabled fluorescence-guided resection of malignant brain tumors using TPS, and the fluorescence intensity of tumors correlated with the TPS concentrations in tissues. These results suggest that TPS is a useful photosensitizer for both intraoperative fluorescence diagnosis and photodynamic therapy.

Brain tumours in Ho Chi Minh City

A series of 65 intracranial tumours operated on, and followed by, the same surgical team during 7 years is presented as a retrospective analysis (1987-1994). Among these patients, only 38 had a diagnosis based upon computed tomography (CT) scan because it was not until 1991 that the first CT scanner was set up in Ho Chi Minh City. Many patients were drowsy or comatose prior to operation due to lack of specialists' intervention or tardy diagnosis and evacuation from remote provincial hospitals. All operations were satisfactory despite the lack of many essential instruments. The histological diagnosis followed the classification proposed by Zulch KJ.(1) Intratumoural calcification has in no case been seen on X-rays or on histological specimens. Operative mortality rate was nil. Although not all the patients with malignant tumours could be followed up, the data available concerning their survival time and the quality of life seems similar to that observed in other reports.

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.

Photodynamic effects of SIM01, a new sensitizer, on experimental brain tumors in rats

BACKGROUND

Glioblastomas are the third most common cause of cancer death in patients between 15 and 35 years old. Literature suggests that PDT could represent a promising treatment, providing that sensitizers could accumulate within the cancer tissues despite the blood-brain barrier.

METHODS

Distribution and PDT effect of SIM01, a promising photosensitizer, have been evaluated on orthotopic C6 tumor model in rats by comparison with HPD and m-THPC. Pharmacokinetics had been analyzed with fluorescence and ROS. Photodynamic treatment was done using a 630-nm light with an energy density of 100 J cm(-2) for HPD and a 652-nm light with an energy density of 20 J cm(-2) for m-THPC and SIM01.

RESULTS

The correlation between fluorescence and ROS dosimetry was found to be excellent. An optimal concentration was found after 12 hours for SIM01 (4 mg/kg), 24 hours for HPD (10 mg/kg), and 48 hours for m-THPC (4 mg/kg). The best normal tissue/cancer ratio of concentration had been found after 12 hours for SIM01 and 48 hours for HPD and m-THPC. Pathological examinations after PDT showed that the criteria for histology of glioblastic origin were absent in SIM01-treated rats 12 hours after injection but were present in 50% of rats treated 24 hours after injection and in all after a 48-hour delay. Mean survival of rats treated 12 or 24 hours after SIM01 injection was significantly improved compared with controls, HPD-, or m-THPC-treated groups. Survival of rats treated 12 or 24 hours after SIM01 injection reached 20 days but decreased for longer delays. On the contrary, survival reached 18 days at the maximum for rats treated 48 hours after m-THPC or HPD injection.

CONCLUSIONS

Our results confirm that PDT is a promising treatment for glioblastomas. SIM01 efficacy is as efficient as m-THPC but with much more favorable pharmacokinetics.

Uptake and retention of the photosensitizer mono-l-asparthyl chlorine e6 in experimental malignant glioma

The objective of the study was to investigate the potential of mono-L-aspartyl chlorine e6 (NPe6), a water-soluble photosensitizer derived from chlorophyll, for use in photodynamic diagnosis (PDD) of malignant brain tumor. A C6 glioma cell line was transplanted in the SD rat brain to create a brain tumor model. Five days after transplantation, NPe6 was administrated via the tail vein at concentrations ranging from 1.25 to 10 mg/kg; then the skull was opened in the rat brain, the site of tumor transplant was irradiated with a diode laser beam at 664 nm, and the time-course intensity and distribution of emerging fluorescence were observed. Furthermore, the correlation between fluorescence distribution and histopathological findings was investigated in the removed brain. Fluorescence was observed in the site of brain tumor transplant from 5 min after injection, and stable fluorescence was recognized at the site until 4 h after administration. No differences were noted in fluorescence intensity at NPe6 doses of 2.5 mg/kg or more; therefore, it was possible to estimate the optimal dose range. Fluorescence distribution had a clear correlation with tumor cell density, and it was possible to capture the margin of tumor cell invasion with fluorescence. The photosensitizer NPe6 is capable of assessing tumor cell density in malignant glioma tissue in terms of differences in fluorescence intensity. The usefulness of PDD using 5-aminoleveulinic acid during surgery for malignant glioma has been recognized in recent years. The results of the present study suggested the potential of NPe6 as a promising photosensitizer for use in PDD for accurate grasp of the extent of removal during the course of malignant glioma surgery.

Massive apoptotic cell death of human glioma cells via a mitochondrial pathway following 5-aminolevulinic acid-mediated photodynamic therapy

The basic mechanism of cell death induced by 5-aminolevulinic acid (5-ALA)-mediated photodynamic therapy (PDT) (ALA-PDT) in glioma cells has not been fully elucidated. In this study, the details of the cell death mechanism induced by ALA-PDT were investigated in three human glioma cell lines (U251MG, U87MG, and U118MG) in vitro. To evaluate the manner of accumulation of protoporphyrin IX (PpIX), intracellular PpIX contents were measured by flow cytometry after incubation with 5-ALA. To analyze the mechanism of cell death, U251MG cells were assayed by the terminal deoxynucleotidyl transferase-mediated dUTP-FITC nick end-labeling (TUNEL) method, and the caspase activity was measured after ALA-PDT. Furthermore, the mitochondrial membrane potential (MMP) and the release of mitochondrial cytochrome c were determined. PpIX fluorescence reached a plateau 4 h after exposure to 5-ALA. The proportion of dead cells increased with increases in the dosage of light. These cells were confirmed by TUNEL staining to be apoptotic. Increases in the activity of both caspase-3 and -9, a decrease in MMP, and a marked increase in cytochrome c in the cytosolic fraction were found after cells were subjected to PDT. These results indicate that a dysfunction of MMP is followed by mitochondrial cytochrome c release, which triggers apoptosis through a mitochondrial pathway. ALA-PDT induces massive apoptosis due to the direct activation of a mitochondrial pathway, which is resistant to many anti-apoptotic processes, in human glioma cells. This finding implies that ALA-PDT is a promising therapy for the treatment of apoptosis-reluctant tumors such as malignant gliomas.

Monitoring of Singlet Oxygen Is Useful for Predicting the Photodynamic Effects in the Treatment for Experimental Glioma

PURPOSE

Singlet oxygen ((1)O(2)) generated in photodynamic therapy (PDT) plays a very important role in killing tumor cells. Using a new near-IR photomultiplier tube system, we monitored the real-time production of (1)O(2) during PDT and thus investigated the relationship between the (1)O(2) production and photodynamic effects.

EXPERIMENTAL DESIGN

We did PDT in 9L gliosarcoma cells in vitro and in an experimental tumor model in vivo using 5-aminolevulinic acid and nanosecond-pulsed dye laser. During this time, we monitored (1)O(2) using this system. Moreover, based on the (1)O(2) monitoring, we set the different conditions of laser exposure and investigated whether they could affect the tumor cell death.

RESULTS

We could observe the temporal changes of (1)O(2) production during PDT in detail. At a low fluence rate the (1)O(2) signal gradually decreased with a low peak, whereas at a high fluence rate it decreased immediately with a high peak. Consequently, the cumulative (1)O(2) at a low fluence rate was higher, which thus induced a strong photodynamic effect. The proportion of apoptosis to necrosis might therefore be dependent on the peak and duration of the (1)O(2) signal. A low fluence rate tended to induce apoptotic change, whereas a high fluence rate tended to induce necrotic change.

CONCLUSIONS

The results of this study suggested that the monitoring of (1)O(2) enables us to predict the photodynamic effect, allowing us to select the optimal laser conditions for each patient.

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

Invasive intracranial tumors, particularly malignant gliomas, are very difficult to eradicate surgically and carry a dismal prognosis. The vast majority relapse locally indicating that their cure is dependent on radical and complete local excision. However, their ability to invade and hide among normal brain tissue, our inability to visualize and detect them, the low tolerance of brain tissue to ionizing radiation and the presence of the blood brain barrier are the main causes of our failure to eradicate them. Photodynamic detection with 100% specificity and more than 80% sensitivity offers an excellent chance of visualizing camouflaged tumor nests. Also, photodynamic therapy offers a very good chance of targeted destruction of the remaining tumor cells safely following surgical excision and may double the survival of patients harboring these awful tumors. More work needs to be done to refine this promising technology to exploit it to its full potential.

Gamma-linolenic acid therapy of human gliomas

OBJECTIVES

We investigated the effect of intratumoral administration of gamma-linolenic acid (GLA) in human gliomas.

METHODS

We evaluated the effect of the administration of 1 mg of GLA for 7 d via a cerebral reservoir placed into the tumor bed or by direct intratumoral delivery in nine patients who had grade 4 disease and recurrent glioma after surgery, radiation, or chemotherapy.

RESULTS

There was some, but not dramatic, improvement in patients' survival. No significant prolongation of life span was expected considering the advanced nature of the disease. Nevertheless, it was encouraging that GLA produced no significant side effects in any patient. Regression of the cerebral gliomas was visualized on computed tomography and magnetic resonance imaging.

CONCLUSIONS

Based on results of the present and previous studies, we believe that GLA is a safe antitumor agent and that higher doses of GLA should be investigated in future studies.

2-[1-hexyloxyethyl]-2-devinyl pyropheophorbide-a (HPPH) in a nude rat glioma model: implications for photodynamic therapy

BACKGROUND AND OBJECTIVE

In this study, we evaluated 2-[1-hexyloxyethyl]-2-devinyl pyropheophorbide-alpha (HPPH or Photochlor) as a photosensitizer for the treatment of malignant gliomas by photodynamic therapy (PDT).

STUDY DESIGN/MATERIALS AND METHODS

We performed in vivo reflection spectroscopy in athymic rats to measure the attenuation of light in normal brain tissue. We also studied HPPH pharmacokinetics and PDT effects in nude rats with brain tumors derived from stereotactically implanted U87 human glioma cells. Rats implanted with tumors were sacrificed at designated time points to determine the pharmacokinetics of HPPH in serum, tumor, normal brain, and brain adjacent to tumor (BAT). HPPH concentrations in normal brain, BAT and tumor were determined using fluorescence spectroscopy. Twenty-four hours after intravenous injection of HPPH, we administered interstitial PDT treatment at a wavelength of 665 nm. Light was given in doses of 3.5, 7.5 or 15 J/cm at the tumor site and at a rate of 50 mW/cm.

RESULTS

In vivo spectroscopy of normal brain tissue showed that the attenuation depth of 665 nm light is approximately 30% greater than that of 630 nm light used to activate Photofrin, which is currently being evaluated for PDT as an adjuvant to surgery for malignant gliomas. The t1/2 of disappearance of drug from serum and tumor was 25 and 30 hours, respectively.

CONCLUSION

Twenty-four hours after injection of 0.5 mg/kg HPPH, tumor-to-brain drug ratios ranged from 5:1 to 15:1. Enhanced survival was observed in each of the HPPH/PDT-treated animal groups. These data suggest that HPPH may be a useful adjuvant for the treatment of malignant gliomas.

Evaluation of brain toxicity following near infrared light exposure after indocyanine green dye injection

Indocyanine green (ICG) has excellent safety records and is widely used in medical diagnosis. Recently, a new method has been developed to estimate cerebral blood flow (CBF) using ICG in combination with near-infrared spectroscopy (NIRS). The new technique may be of wide clinical interest, as it is noninvasive and easy to perform at the bedside in stroke patients. Additionally, ICG with the use of specific wavelength lasers is documented to be effective in photodynamic therapy (PDT). Under normal conditions ICG does not cross the intact blood brain barrier (BBB). However, in patients with brain injuries where the BBB may be disturbed, ICG could accumulate in brain parenchyma and in combination with NIR-light exposure, phototoxicity could occur. The aim of the present study was to examine the possible toxicity of ICG in combination with NIRS in a specific setting for CBF measurements. In five rats with mannitol induced BBB breakdown no traces of ICG were found during spectrophotometric analysis of the brain cell suspensions. In ten rats with disrupted BBB there were no significant increases of brain temperature or histological signs of brain damage following 1 h NIR-light exposure after ICG injection. The existing literature concerning the application of ICG in combination with NIR light is reviewed.

Competitive uptake of porphyrin and LDL via the LDL receptor in glioma cell lines: flow cytometric analysis

We examined the simultaneous uptake of porphyrin and (LDL) by four established cell lines of glioma and normal fibroblasts using flow cytometry (FCM). The results indicated porphyrin and LDL showed competitive conjugation with the LDL receptor. These results support the theory of the porphyrin uptake via the LDL receptor.

Mechanism of photodynamic activity of pheophorbides

Plasmid DNA is efficiently photocleaved by sodium pheophorbides (Na-Phdes) a and b in the absence of oxygen as well as in the presence of oxygen. Fluorescence microscopic observation shows a rapid incorporation of Na-Phde a into nuclei, mitochondria, and lysosome of human oral mucosa cells. In contrast Na-Phde b is incorporated only into the plasma membrane. The photodynamic activity of these pigments in living tissues is probably determined by the monomeric pigment molecules formed in hydrophobic cellular structures and involves two types of reactions: (i) direct electron transfer between DNA bases (especially guanine) and pheophorbide singlet excited state, and (ii) indirect reactions mediated by reactive oxygen species, including singlet oxygen whose production from molecular oxygen is sensitized by the Na-Phdes triplet state. A preliminary report has appeared in "Photodynamic Therapy of Cancer II," Proc. SPIE 2325, 416-424 (1994).

Photodynamic therapy of human glioma spheroids using 5-aminolevulinic acid

The response of human glioma spheroids to 5-aminolevulinic acid (ALA)-mediated photodynamic therapy (PDT) is investigated. A two-photon fluorescence microscopy technique is used to show that human glioma cells readily convert ALA to protoporphyrin IX throughout the entire spheroid volume. The central finding of this study is that the response of human glioma spheroids to ALA-mediated PDT depends not only on the total fluence, but also on the rate at which the fluence is delivered. At low fluences (< or = 50 J cm-2), lower fluence rates are more effective. At a fluence of 50 J cm-2, near-total spheroid kill is observed at fluence rates of as low as 10 mW cm-2. The fluence rate effect is not as pronounced at higher fluences (> 50 J cm-2), where a favorable response is observed throughout the range of fluence rates investigated. The clinical implications of these findings are discussed.

Neurosurgery at the Royal Melbourne Hospital

The Department of Neurosurgery of the Royal Melbourne Hospital (RMH) is a major neurosurgery program and academic leader in Australasia. In 1998, the RMH marked its 150th anniversary. The department of neurosurgery was established in 1945 under the direction of R.S. Hooper and has produced many distinguished neurosurgeons since its founding. The department is currently directed by Andrew Kaye, who is also the James Stewart Professor of Surgery at the University of Melbourne. In 1997-1998, the neurosurgery department received 2930 admissions and performed 2225 operations, with 11 neurosurgeons on staff and a strong focus on subspecialization. The neurosurgeons have varying time commitments to the hospital and to research, but many are on site full-time. The RMH is a university teaching hospital as well as a public hospital; therefore, there is no financial burden for any patient. The RMH is closely linked to the adjacent Melbourne Private Hospital, where privately insured patients are treated. The department of neurosurgery maintains close links with the departments of neurology, ophthalmology, and neuropsychiatry, which together form the Melbourne Neuroscience Centre. There is a strong emphasis on undergraduate and postgraduate teaching, as well as clinical and laboratory research. Neurosurgery trainees are encouraged to undertake laboratory research and pursue higher academic degrees. Despite economic restraints, the department continues to grow in strength, and we remain optimistic of exciting times ahead for neurosurgery at the RMH in the new millennium.

Raman spectroscopic study of microcosmic photodamage of the space structure of DNA sensitized by Yangzhou haematoporphyrin derivative and Photofrin II

After calf thymus DNA has been photodamaged by Yangzhou haematoporphyrin derivative (YHPD) or Photofrin II, the Raman characteristic frequencies and the intensities of the bands assigned to various groups of the components of DNA change considerably. As a result of damage, homogeneous B-form calf thymus DNA becomes a mixture containing: (1) modified B-form DNA, which is shorter than the original because of double-helical DNA scission; (2) single-stranded DNA due to the breakage of some H-bonds and the lack of some bases, etc.

Optical coherence tomography for neurosurgical imaging of human intracortical melanoma

OBJECTIVE

Intraoperative identification of brain tumors and tumor margins has been limited by either the resolution of the in vivo imaging technique or the time required to obtain histological specimens. Our objective was to evaluate the feasibility of using optical coherence tomography (OCT) as a high-resolution, real-time intraoperative imaging technique to identify an intracortical melanoma.

INSTRUMENTATION

OCT is a new, noncontact, high-speed imaging technology capable of resolutions on the micrometer scale. OCT is analogous to ultrasound B-mode imaging, except that reflections of infrared light, rather than sound, are detected. OCT uses inherent tissue contrast, rather than enhancement with dyes, to differentiate tissue types. The compact, fiberoptic-based design is readily integrated with surgical instruments.

METHODS

A portable handheld OCT surgical imaging probe has been constructed for imaging within the surgical field. Cadaveric human cortex with metastatic melanoma was harvested and imaged in two and three dimensions. Changes in optical backscatter intensity were used to identify regions of tumor and to locate tumor margins. Structures within the optical coherence tomographic images were compared with the histological slides.

RESULTS

Two-dimensional images showed increased optical backscatter from regions of tumor, which was quantitatively used to determine the tumor margin. The images correlated well with the histological findings. Three-dimensional reconstructions revealed regions of tumor penetrating normal cortex and could be resectioned at arbitrary planes. Subsurface cerebral vascular structures could be identified and were therefore avoided.

CONCLUSION

OCT can effectively differentiate normal cortex from intracortical melanoma based on variations in optical backscatter. The high-resolution, high-speed imaging capabilities of OCT may permit the intraoperative identification of tumor and the more precise localization of tumor margins.

Cell cycle dependency of porphyrin uptake in a glioma cell line

We used a two-color analysis system to assess the porphyrin uptake and DNA content in four established cell lines of glioma employing flow cytometry (FCM). The FCM study revealed porphyrin uptake in all cells, regardless of the phase of the cell cycle they were in. However, those in the G0/G1 phase showed moderate uptake of porphyrin and those in the G2/M phase showed a higher uptake. These results indicated the advantage of using porphyrin as the carrier of tumor targeting agents as a therapeutic strategy for malignant tumors.

Manganese-metalloporphyrin (ATN-10) as a tumor-localizing agent: magnetic resonance imaging and inductively coupled plasma atomic emission spectroscopy study with experimental brain tumors

OBJECTIVE

We examined whether selective tumor accumulation of a novel manganese-metalloporphyrin (ATN-10) occurs in Fisher rats bearing intracerebral 9L gliomas.

METHODS

After intravenous administration of ATN-10, magnetic resonance imaging of brains with tumors or nontumoral vasogenic brain edema was performed. Tissue manganese concentrations were measured by inductively coupled plasma atomic emission spectroscopy until 48 hours after administration of ATN-10, to evaluate its uptake in tumor, normal brain, and peritumoral brain tissue.

RESULTS

In magnetic resonance imaging scans, early enhancement was observed in both tumor tissue and regions of nontumoral vasogenic brain edema at 5 minutes after ATN-10 administration. However, delayed enhancement was noted only in tumor tissue, at 24 hours after intravenous injection of ATN-10. Comparison of rat brain specimens and 24-hour magnetic resonance imaging scans revealed that only the viable portions of tumors were enhanced with ATN-10; necrotic regions and areas of peritumoral brain tissue and nontumoral vasogenic edema were not. Significantly greater uptake of ATN-10 was found in tumor samples, compared with normal and peritumoral brain tissue, at 24 hours. A high tumor/normal brain tissue ratio (10.4) was achieved at 24 hours.

CONCLUSION

ATN-10, a manganese-metalloporphyrin, is a potentially useful tumor-localizing agent that accumulates and is preferentially retained in viable tumor tissue.

Binding of monomeric and oligomeric porphyrins to human glioblastoma (U-87MG) cells and their photosensitivity

The binding of monomeric (Hp) and oligomeric (PHE) forms of porphyrin to glioblastoma (U-87MG) cells and the photosensitization of these cells have been studied. Upon binding to U-87MG cells, Hp and PHE exhibited fluorescence bands at 615 and 636 nm, respectively. The fluorescence and absorption spectra of Hp, HpD and PHE, measured in different solvents, suggest that the 615 nm band may arise due to the binding of monomeric as well as aggregated forms of porphyrin to the hydrophilic sites in the cells whereas the 636 nm band may be due to the binding of an aggregated form of porphyrin to the hydrophobic sites. The photosensitivity of cells and photo-induced lipid peroxidation were measured as a function of light dose. Cells were found most photosensitive to PHE followed by HpD and Hp. The photosensitivity of cells correlates well with the fluorescence intensity of cell bound dye at 636 nm. These results suggest that the binding of the oligomeric component of HpD to hydrophobic sites in the cells is responsible for the enhancement in the photosensitivity.

Lumboperitoneal shunting for pseudotumor cerebri

To clarify the appropriate role of lumboperitoneal (LP) shunting in the surgical management of pseudotumor cerebri (PTC), we retrospectively analyzed the clinical data from 30 patients who underwent this procedure. We found LP shunting to be an effective means of acutely lowering intracranial pressure. Symptoms of increased intracranial pressure improved in 82% of patients. Among 14 eyes with impaired visual acuity, 10 (71%) improved by at least two lines. Worsening of vision occurred in only one eye. Of 28 eyes with abnormal Goldmann perimetry, 18 (64%) improved and none worsened. The incidence of serious complications was low. The major drawback of LP shunting was the need for frequent revisions in a few patients. The reason for poor shunt tolerance in certain individuals is unclear. In PTC, LP shunting should be considered as the first surgical procedure for patients with severe visual loss at presentation or with intractable headache (with or without visual loss). After shunting it is important to identify patients who are shunt intolerant.

Interstitial laser thermotherapy: developments in the treatment of small deep-seated brain tumors

New technical advances have made feasible the utilization of laser to destroy deep-seated brain tumors under real-time monitoring. Experience with interstitial laser thermotherapy (ILTT) in animal and clinical studies has been obtained. These studies are summarized and the future potential of ILTT in neurosurgery is discussed.

Photodynamic therapy within edematous brain tissue: considerations on sensitizer dose and time point of laser irradiation

Photosensitizer is known to spread with vasogenic edema fluid arising from a cerebral lesion (Neurosurg 33:1075-1082, 1993), which may be essential for sensitizing malignant cells outside the main tumor mass. The present experiments seek to elucidate whether resultant necrosis of perifocal brain tissue after laser irradiation follows a corresponding time pattern and whether damage depends on the photosensitizer dose. Male Wistar rats were anaesthetized with chloralhydrate for venous cannulation, craniotomy and focal cold lesion in order to induce vasogenic edema. Simultaneously, Photofrin II (PF II) was administered at a dose of 5 mg kg-1. The animals were re-anaesthetized after either 4, 12 or 24 h for the irradiation of lesion and perifocal tissue with 200 J cm-2 of laser light (630 nm). The brains of other animals were irradiated 4 h after cold lesion with 200 J cm-2 after receiving either 0, 2.5 or 5 mg kg-1 PF II (all groups: n = 6). Resultant necrosis was assessed planimetrically in serial coronal cryosections of brains perfusion fixed 24 h after irradiation. Necrosis was significantly enhanced with irradiation 4 h after cold lesion and photosensitizer (avg. area +/- SD: 4.3 +/- 0.7 mm2) compared with lesion only (0.84 +/- 0.2 mm2). Maximal necrosis (6.3 +/- 1.6 mm2) occurred with irradiation 12 h after lesion, whereas necrosis was only slightly increased with irradiation at 24 h (2.8 +/- 0.4 mm2). Furthermore, the area of necrosis was dependent on the sensitizer dose (0 mg kg-1: 0.7 +/- 0.3 mm2, 2.5 mg kg-1: 2.09 +/- 0.2 mm2, 5 mg kg-1: 4.3 +/- 0.7 mm2; all differences p < 0.05). Therefore, to prevent unwanted side-effects such as necrosis of edematous but otherwise healthy, peritumoral tissue in the treatment of malignant cerebral tumors by PDT, tribute should be paid to the possibility of time and dose dependent sensitization of the perifocal tissue after i.v. administration of photosensitizer.

Photodynamic therapy of brain tumors

Photodynamic therapy (PDT) for the treatment of a variety of brain tumors, particularly gliomas, has been extensively investigated in laboratory studies and has been studied in clinical trials. The main advantage of PDT lies in its ability to select out tumor cells that are infiltrating brain parenchyma and that are responsible for local tumor recurrence, the major therapeutic dilemma in the treatment of gliomas. PDT has been shown to be safe clinically but adequate trials have yet to be undertaken to prove its efficacy and much work remains to be done to optimize treatment. The laboratory studies and clinical trials involving PDT in the treatment of cerebral tumors, particularly the commonest brain tumors, gliomas, are discussed.

Photodynamic therapy for malignant newly diagnosed supratentorial gliomas

We report the use of photodynamic therapy (PDT) in the treatment of 20 patients with newly diagnosed malignant supratentorial gliomas. There were 10 males and 10 females; their mean age was 56 years and the mean Karnofsky score was 75. Eleven patients had glioblastoma multiforme (GBM) and 9 had malignant astrocytoma (MA). Intravenous porphyrin photosensitizer was administered 12-36 h prior to surgery and photoillumination. At operation all patients had the tumor subtotally resected followed by intraoperative cavitary photoillumination. Interstitial photoillumination using fibers with 2-cm diffusing tips supplemented the cavitary illumination in 3 patients. The total light energy delivered ranged from 570 to 4050 J (median = 1260 J). The energy density ranged from 15 to 110 J/cm2 (median = 32 J/cm2). All but two had postoperative radiation therapy (5000 cGy in 5 weeks). No untoward effects of radiation in conjunction with PDT were identified. There was 1 postoperative death and 1 patient had a persistent increase in postoperative neurological deficit. The median survival of these 20 patients with newly diagnosed malignant gliomas was 44 weeks with a 1- and 2-year survival of 40 and 15%, respectively. The median survival of these patients with newly diagnosed GBM was 37 weeks with a 1- and 2-year survival of 35 and 0%, respectively, and the median survival for MA was 48 weeks with a 1- and 2-year survival of 44 and 33%, respectively. Six patients with a Karnofsky score of > 70 who received a light dose of > 1260 J (mean energy density = 62 +/- 20 SEM J/cm2) had a median survival of 92 weeks with a 1- and 2-year survival of 83 and 33% respectively. Patients with malignant astrocytic tumors (GBM and MA) have a very poor prognosis. Nevertheless PDT is safe in newly diagnosed patients with supratentorial malignant gliomas who undergo postoperative radiation and appears to prolong survival in selected patients when an adequate light dose is used. Further improvement in survival may be expected with higher light doses.

Interstitial laser thermotherapy in neurosurgery: a review

One of the most recent laser treatment modalities in neurosurgery is interstitial laser thermotherapy (ILTT). In this review, experimental and clinical studies concerning intracranial ILTT are discussed. Two methods for intra-operative control of the laser induced lesions are described; i.e., computer-controlled power delivery, using a thermocouple that is positioned interstitially at the periphery of the tumour to maintain the desired temperature at that point, and MRI, to visualise the extent of the thermal lesions induced by ILTT. The results show that ILTT using a Nd: YAG laser is easy and relatively effective in the treatment of small deep-seated brain tumours with minimal risk and complications. This review is concluded with suggestions for further improvement of this treatment modality.

Damage threshold of normal rat brain in photodynamic therapy

Normal brain tissue response to photodynamic therapy (PDT) must be quantified in order to implement PDT as a treatment of brain neoplasm. We therefore calculated the threshold for PDT-induced tissue necrosis in normal brain using Photofrin (porfimer sodium, Quadralogic Technologies Inc., Vancouver, BC) as the photosensitizer. The absolute light fluence-rate distribution for superficial irradiation and effective attenuation depth were measured in vivo using an invasive optical probe. Photosensitizer uptake in cerebral cortex was measured with chemical extraction and fluorometric analysis. Photodynamic therapy-induced lesion depths at various drug dose levels were measured as a biological end point. The PDT threshold for normal brain necrosis was calculated as in the magnitude of 10(16) photons/cm3. Thus normal rat brain is extremely vulnerable to PDT damage. This suggests that extra precautions must be exercised when PDT is used in brain.

Lumboperitoneal shunt for the treatment of pseudotumor cerebri

We conducted a retrospective study of 27 patients with pseudotumor cerebri (PTC) treated with at least one lumboperitoneal shunt (LPS) to ascertain the efficacy of this treatment. The average duration of follow-up for this population was 77 months (median, 47 months), with a range of 21 to 278 months. A functioning LPS was successful in alleviating symptoms in all patients studied, and no patient with a functioning shunt complained of shunt-related symptoms, such as low-pressure headache or abdominal pain, within 2 months after the shunt was performed. Twelve patients (44%) required no revisions. The number of revisions among the 15 patients (56%) who required them ranged from 1 (5 patients) to 13 (1 patient). Three of these patients required 35 of the 66 total shunt revisions (53%). There were no major complications from LPS, other than failure of the shunt, even in patients who required multiple shunts. We conclude that placement of a lumboperitoneal shunt is satisfactory treatment for the majority of patients with PTC who require surgical therapy for the disorder, even though some patients ultimately require multiple shunt revisions.

The Richard C. Schneider Lecture. New dimensions of neurosurgery in the realm of high technology: possibilities, practicalities, realities

Fueled by a buoyant economy, popular attitudes and demands, and parallel progress in transferable technical and biological areas, neurosurgery has enjoyed a remarkable quarter of a century of progress. Developmental trends in the discipline have included the following: 1) a refinement of preoperative definition of the structural substrate, 2) miniaturization of operative corridors, 3) reduction of operative trauma, 4) increased effectiveness at the target site, and 5) incorporation of improved technical adjuvants and physical operative tools into treatment protocols. In particular, the computer has become a formidable ally in diagnostic and surgical events. Trends in technical development indicate that we are entering an exciting era of advanced surgery of the human cerebrum, which is heralded by the following: 1) current developments in areas of imaging, sensors, and visualization; 2) new devices for localization and navigation; 3) new capabilities for action at the target point; and 4) innovative concepts related to advanced operative venues. Imaging has provided structurally based surgical maps, which now are being given the new dimension of function in complex and integrated formats for preoperative planning and intraoperative tactical direction. Cerebral localization and navigation based on these advances promise to provide further refinement to the field of stereotactic neurosurgery, as linked systems are superseded by more flexible nonlinked methodologies in functionally defined volume-oriented navigational databases. Target point action now includes not only ablative capabilities through micro-operative methods and the use of stereotactically directed high-energy forms but also the emergence of restorative capabilities through applications of principles of genetic engineering in the areas of molecular and cellular neurosurgery. Complex, dedicated, and self-contained operative venues will be required to optimize the emergence and development of these computer-oriented micro/stereotactic capabilities, which appear to be unavoidably required as locales for the practice and development of virtual reality-based stations for operative rehearsal, simulation, training, and, ultimately, enhancement of operative events through robotic interfaces. Primary impetus for progress has relied upon new combinations of technologies, disciplines, and industries. Philosophical and practical problems include the spectrum of availability of these methods to the population at large, the training of individuals to properly administer these methods, defining the acceptable envelope of expertise, and maintaining suitable delivery and progress while containing spiraling costs. Advanced neurological surgery and the use and development of high-technology adjuvants require a robust economy that has a populace willing to invest in the luxury of such developments. The current socioeconomic situation is fragile from the standpoint of both economics and attitudes of the patients and health care providers, with diversion of economic resources, redistribution of funding bases, modification of patient referrals, practice styles, and service attitudes undermining progress. Economic pressures have brought high-technology methods under great scrutiny regarding their effectiveness and cost-effectiveness. Reform proposals have specifically targeted technology-oriented services, and the Office of Technology Assessment has recommended increasing the use of managed care providers who look to information on cost-effectiveness and clinical practice guidelines to establish efficient management strategies and issue "report cards." Although the premise is laudable and "gimmickry" needs to be identified, it might be argued that such scrutiny and control might be overbearing and overused, impeding appropriate delivery and progress.

Light-emitting diodes as a light source for intraoperative photodynamic therapy

The development of more cost-effective light sources for photodynamic therapy of brain tumors would be of benefit for both research and clinical applications. In this study, the use of light-emitting diode arrays for photodynamic therapy of brain tumors with Photofrin porfimer sodium was investigated. An inflatable balloon device with a light-emitting diode (LED) tip was constructed. These LEDs are based on the new semiconductor aluminum gallium arsenide. They can emit broad-spectrum red light at high power levels with a peak wavelength of 677 nm and a bandwidth of 25 nm. The balloon was inflated with 0.1% intralipid, which served as a light-scattering medium. Measurements of light flux at several points showed a high degree of light dispersion. The spectral emission of this probe was then compared with the absorption spectrum of Photofrin. This analysis showed that the light absorbed by Photofrin with the use of the LED source was 27.5% of that absorbed with the use of the monochromatic 630-nm light. Thus, to achieve an energy light dose equivalent to that of a laser light source, the LED light output must be increased by a factor of 3.63. This need for additional energy is the difference between a 630- and 677-nm absorption of Photofrin. Using the LED probe and the laser balloon adapter, a comparison of brain stem toxicity in canines was conducted. LED and laser light showed the same signs of toxicity at equivalent light energy and Photofrin doses. The maximal tolerated dose of Photofrin was 1.6 mg/kg, using 100 J/cm2 of light energy administered by laser or LED. This study concludes that LEDs are a suitable light source for photodynamic therapy of brain tumors with Photofrin. In addition, LEDs have the potential to be highly efficient light sources for second-generation photosensitizers with absorption wavelengths closer to the LED peak emission.

Preliminary results of photodynamic therapy for recurrent nasopharyngeal carcinoma

Photodynamic therapy (PDT) is a promising new modality in the treatment of cancer. In Hong Kong where nasopharyngeal carcinoma (NPC) is endemic, radiotherapy has been the primary treatment of choice. For recurrent disease after radiotherapy, there is no effective treatment. This latter report summarizes our initial experience in using PDT for these patients. Twelve patients (three females and nine males) with ages ranging from 33 to 65 years were treated with an infusion of hematoporphyrin derivative (5 mg/kg) 48-72 h before exposure to 200 J/cm2 light (wavelength, 630 nm) delivered from a gold vapor laser. All 12 patients showed a dramatic response as judged by computed tomography or magnetic resonance imaging at 6 months post-PDT. Of the eight patients in whom cure was aimed for, three remained disease-free at 9-12 months after a single treatment. Three of the remaining four patients achieved useful palliation. Skin hypersensitivity occurred in two patients and was the only significant complication encountered. This experience indicates that PDT can be an encouraging palliative or definitive management for recurrent superficial NPC.

Selective tumor kill of cerebral glioma by photodynamic therapy using a boronated porphyrin photosensitizer

The prognosis for patients with the high-grade cerebral glioma glioblastoma multiforme is poor. The median survival for primary tumors is < 12 months, with most recurring at the site of the original tumor, indicating that a more aggressive local therapy is required to eradicate the unresectable "nests" of tumor cells invading into adjacent brain. Two adjuvant therapies with the potential to destroy these cells are porphyrin-sensitized photodynamic therapy (PDT) and boron-sensitized boron neutron capture therapy (BNCT). The ability of a boronated porphyrin, 2,4-(alpha, beta-dihydroxyethyl) deuteroporphyrin IX tetrakiscarborane carboxylate ester (BOPP), to act as a photosensitizing agent was investigated in vitro with the C6 rat glioma cell line and in vivo with C6 cells grown as an intracerebral tumor after implantation into Wistar rats. These studies determined the doses of BOPP and light required to achieve maximal cell kill in vitro and selective tumor kill in vivo. The data show that BOPP is more dose effective in vivo by a factor of 10 than the current clinically used photosensitizer hematoporphyrin derivative and suggest that BOPP may have potential as a dual PDT/BNCT sensitizer.

Photodynamic therapy of brain tumors

Photodynamic therapy (PDT) is a binary treatment modality suitable for various malignant tumors including brain. It involves the selective uptake of a photosensitizer into tumor followed by intraoperative irradiation of the tumor with light of an appropriate wavelength to cause activation of the sensitizer and subsequent selective tumor destruction. PDT has been extensively investigated in laboratory studies and has been used in clinical trials to treat a variety of brain tumors, particularly gliomas. The main advantage of PDT lies in its ability to select out infiltrating tumor cells that are responsible for local tumor recurrence. The therapy has been shown to be safe clinically but adequate trials have yet to be undertaken to prove its efficacy and much work remains to be done to optimize treatment. The biological basis, laboratory studies, and clinical trials involving PDT in the treatment of cerebral tumors are discussed.

Photodynamic therapy for recurrent supratentorial gliomas

We have used photodynamic therapy (PDT) in the treatment of 56 patients with recurrent supratentorial gliomas who had failed radiation therapy and who were candidates for palliative reoperation. There were 34 males and 22 females; their mean age was 41 years and the mean Karnofsky score was 79. Thirty-two patients had glioblastoma multiforme (GBM), 14 had malignant astrocytoma (MA), 6 had malignant mixed glioma (MM), and 4 had ependymoma (EP). Porphyrin photosensitizer was administered intravenously (i.v.) 12-36 hours prior to photoillumination. All patients had the recurrent tumor subtotally resected or cyst drained at surgery followed by intraoperative cavitary photoillumination. In 15 cases interstitial photoillumination using fibers with 2 cm diffusing tips supplemented the cavitary illumination. The total light energy delivered ranged from 440 to 4,500 Joules (J) (median = 1,800 J). The energy administered ranged from 120 to 150 J per fiber and the linear energy density ranged from 65 to 450 J/cm. The energy density ranged from 8 to 110 J/cm2 (median = 38 J/cm2). There were two postoperative deaths and three patients were left with a persistent increase in their postoperative neurological deficit. The post-PDT median survival of patients with recurrent GBM was 30 weeks with a 1- and 2-year actuarial survival of 18% and 0%, respectively. The median survival of patients with recurrent GBM from first diagnosis was 118 weeks with a 1- and 2-year actuarial survival of 82% and 57%, respectively. The post-PDT median survival of patients with recurrent MA was 44 weeks with a 1- and 2-year actuarial survival of 43% and 36%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Local application of gamma-linolenic acid in the treatment of human gliomas

gamma-Linolenic acid (GLA) has been shown to have selective tumoricidal action both in vitro and in vivo. Earlier, in a limited clinical study, we have demonstrated that intra-tumoral administration of GLA can induce regression of human gliomas. In an extension of this study, we evaluated the effect of intra-cerebral injection of GLA on normal dog brain and in 15 patients with malignant gliomas. Histopathological examination revealed that GLA is not cytotoxic to the normal dog brain cells. Administration of 10 mg of GLA via a cerebral reservoir placed in the tumour bed, at the rate of 1 mg/day over a period of 10 days, revealed that GLA is not only safe and non-toxic but can also regress cerebral gliomas as evaluated by computerised tomography and increased survival of the patients by 1.5-2 years. Based on these results and our earlier in vitro study, we suggest that GLA is a safe anti-tumour agent and recommend its use in the management of human gliomas.

Therapy of glioblastoma multiforme: a cumulative experience of 10 years

PURPOSE

Comparison of the effect of different therapeutic modalities on survival time of patients with glioblastoma multiforme operated on during the last decade (1980-1990).

PATIENTS AND METHODS

The records of 157 consecutive patients with the histological diagnosis of glioblastoma multiforme were analysed for survival with respect to age of patients, extent of surgery, influence of re-operation and adjuvant postoperative treatment. The latter included fractionated radiotherapy, chemotherapy (BCNU. CCNU with Vincristine) and photodynamic therapy (PDT).

RESULTS

Analysis of variance showed a significant effect for survival after macroscopically radical surgery (p = 0.005), postoperative radiotherapy (p < 0.001), chemotherapy (p < 0.01). Low age (p < 0.05) and a postoperative Karnofsky performance score (KPS) > or = 60 (p < 0.001) had a positive influence: the site of tumour and pre-operative presence of seizures had no significant influence (p > 0.1) on survival time.

CONCLUSION

We conclude that the current adequate management of glioblastoma multiforme should include surgical resection followed by adjuvant treatment such as radiotherapy and chemotherapy.

Clinical and preclinical photodynamic therapy

Photodynamic therapy (PDT) is a treatment modality that utilizes a photosensitizing drug activated by laser generated light, and is proving effective for oncologic and nononcologic applications. This report provides an overview of photosensitizers, photochemistry, photobiology, and the lasers involved in photodynamic therapy. Clinical and preclinical PDT studies involving Photofrin and various second generation photosensitizers are reviewed.