Intracavity fractionated balloon brachytherapy in glioblastoma

Fibrin glue mediated direct delivery of radiation sensitizers results in enhanced efficacy of radiation treatment

PURPOSE

Radiation therapy (RT) plays an important role in the treatment of glioblastoma multiforme (GBM). However, inherent intrinsic resistance of tumors to radiation, coupled with the need to consider the tolerance of normal tissues and the potential effects on neurocognitive function, impose constraints on the amount of RT that can be safely delivered. A strategy for augmenting the effectiveness of RT involves the utilization of radiation sensitizers (RS). Directly implanting RS-loaded fibrin glue (FG) into the tumor resection cavity would by-pass the blood brain barrier, potentially enhancing the impact of RT on tumor recurrence. This study investigated the ability of FG to incorporate and release, in non-degraded form, the radiation sensitizers 5-Fluorouracil (5FU) and Motexafin gadolinium (MGd).

METHODS

FG layers were created in a 24-well plate by combining thrombin, fibrinogen, and 5FU or MGd. Supernatants from these layers were collected at various intervals and added to F98 glioma spheroid cultures in 96-well plates. Radiation was applied either before or after RS application as single or fractionated dosages. Spheroid growth was monitored for 14 days.

RESULTS

Combined treatment of FG-released 5FU and RT significantly inhibited spheroid growth compared to RS or RT as a single treatment. As a free drug, MGd demonstrated its efficacy in reducing spheroid volume, but had diminished potency as a released RS. Fractionated radiation was more effective than single dose radiation.

CONCLUSION

Non-degraded RS was released from the FG for up to 72 h. FG-released 5FU greatly increased the efficacy of radiation therapy.

Macrophages as a photosensitizer delivery system for photodynamic therapy: Potential for the local treatment of resected glioblastoma

BACKGROUND

Photodynamic therapy (PDT) efficacy is determined in part by the concentration of photosensitizer (PS) at the treatment site. The blood-brain barrier (BBB) poses a significant limitation on the transport of PS into the post-operative resection region where brain tumors most often recur. Macrophages (Ma), as opposed to free or nanoparticle bound agents, are known to actively migrate to and around tumors, and can therefore be used as delivery vectors for both drugs and photosensitizers.

METHODS

Mouse Ma (RAW264.7) and F98 rat glioma cells were used in all experiments along with the photosensitizer AlPcS2a. Mitomycin-treated Ma were loaded with photosensitizer (PS) and mixed with glioma cells, forming hybrid spheroids. F98 spheroids were incubated with supernatants derived from PS-loaded Ma (MaPS). Light treatment (PDT) was administered at various radiant exposures from a 670 nm diode laser. The growth of both types of spheroids was evaluated by measurement of spheroid volume after 14 days in culture.

RESULTS

PDT on F98 cell spheroid cultures, mediated by either free or PS-released from Ma, demonstrated a significant growth inhibition with supernatants harvested after 4 and 24 h. A significant PDT-induced growth inhibition was demonstrated in the MaPS/F98 hybrid spheroid experiments.

CONCLUSION

Since the efficacy of PDT, mediated by either free or released photosensitizer was comparable, the uptake and released photosensitizer was not degraded. MaPS, incorporated in hybrid tumor spheroids also mediated effective PDT. These results indicate that Ma have potential as an effective vector for photosensitizer delivery to resected brain tumors.

Fibrin glue as a local drug and photosensitizer delivery system for photochemical internalization: Potential for bypassing the blood-brain barrier

BACKGROUND

Chemotherapy has had disappointing results in the treatment of glioblastoma multiforme (GBM). This is in part due to limited systemic drug penetration through the blood-brain barrier. This limitation can be overcome by implantation of drug-loaded hydrogels, such as fibrin glue (FG), directly into the tumor resection cavity. Photochemical internalization (PCI) has been shown to enhance the efficacy of a large number of chemotherapeutic agents, including bleomycin (BLM). This study examined the ability of loaded FG to release BLM and photosensitizer to enable PCI-induced growth inhibition of glioma spheroids in vitro.

MATERIALS AND METHODS

FG layers, loaded with drug and photosensitizer, were formed in wells of a 24-well plate. Supernatants covering the FG layers were harvested after 48 h. F98 glioma spheroids were co-incubated with harvested supernatants for 24 h, followed by light exposure. Spheroid growth was monitored for an additional 14 days.

RESULTS

100% of the drug bleomycin and 90% of the photosensitizer (AlPcS_2a) was released from the FG over a 48 h interval. Spheroid growth was significantly inhibited or completely suppressed by PCI of released drug and photosensitizer in many of the concentration combinations tested. PCI-induced growth inhibition increased with increasing light levels.

CONCLUSIONS

The results demonstrate that both drug and photosensitizer were loaded into and released in a non-degraded form for an extended time period. The growth inhibition caused by FG-released BLM was significantly enhanced by FG-released AlPcS_2a-mediated PCI.

Photosensitizer delivery by fibrin glue: potential for bypassing the blood-brain barrier

Fibrin glue (FG) has potential as a delivery vehicle for photosensitizer directly to the resection cavity, so it may bypass the blood-brain barrier (BBB) and increase the concentration of successfully delivered photosensitizer. A specialized form of photodynamic therapy (PDT), photochemical internalization (PCI), which involves both photosensitizer and chemotherapeutic agent internalization, can locally inhibit the growth of cells. This will allow the reduction of recurrence of malignant gliomas around surgical resection. This study will look at the efficacy of FG loaded with drugs in mediating both PDT and PCI in inhibiting 3-dimensional tumor spheroid growth in vitro. Experiments were conducted on spheroids comprised of F98 glioma cells using photosensitizer AlPcS_2a and chemotherapeutic drug bleomycin (BLM). At 2-, 24-, 48-, and 72-h increments, supernatant covering an FG layer within a well was collected and replaced by fresh medium, then added to spheroid-containing wells, which contained the respective chemicals for PDT and PCI. The wells were then exposed to light treatment from a diode laser, and after, spheroid growth was monitored for a period of 14 days. Significant spheroid growth inhibition was observed in both PDT and PCI modalities, but was far greater in PCI. Additionally, complete growth suppression was achieved via PCI at the highest radiant exposure. Achieving a slow photosensitizer release, significant F98 spheroid inhibition was observed in FG-mediated PDT and PCI. The present study showed BLM-PCI was the most efficacious of the two modalities.

Photochemical Internalization for Intracellular Drug Delivery. From Basic Mechanisms to Clinical Research

Photochemical internalisation (PCI) is a unique intervention which involves the release of endocytosed macromolecules into the cytoplasmic matrix. PCI is based on the use of photosensitizers placed in endocytic vesicles that, following light activation, lead to rupture of the endocytic vesicles and the release of the macromolecules into the cytoplasmic matrix. This technology has been shown to improve the biological activity of a number of macromolecules that do not readily penetrate the plasma membrane, including type I ribosome-inactivating proteins (RIPs), gene-encoding plasmids, adenovirus and oligonucleotides and certain chemotherapeutics, such as bleomycin. This new intervention has also been found appealing for intracellular delivery of drugs incorporated into nanocarriers and for cancer vaccination. PCI is currently being evaluated in clinical trials. Data from the first-in-human phase I clinical trial as well as an update on the development of the PCI technology towards clinical practice is presented here.

Injectable Hydrogels for Localized Chemotherapy and Radiotherapy in Brain Tumors

Overall survival of patients with newly diagnosed glioblastoma (GBM) remains dismal at 16 months with state-of-the-art treatment that includes surgical resection, radiation, and chemotherapy. GBM tumors are highly heterogeneous, and mechanisms for overcoming tumor resistance have not yet fully been elucidated. An injectable chitosan hydrogel capable of releasing chemotherapy (temozolomide [TMZ]) while retaining radioactive isotopes agents (iodine, [¹³¹I]) was used as a vehicle for localized radiation and chemotherapy, within the surgical cavity. Release from hydrogels loaded with TMZ or ¹³¹I was characterized in vitro and in vivo and their efficacy on tumor progression and survival on GBM tumors was also measured. The in vitro release of ¹³¹I was negligible over 42 days, whereas the TMZ was completely released over the first 48 h. ¹³¹I was completely retained in the tumor bed with negligible distribution in other tissues and that when delivered locally, the chemotherapy accumulated in the tumor at 10-fold higher concentrations than when delivered systemically. We found that the tumors were significantly decreased, and survival was improved in both treatment groups compared to the control group. Novel injectable chemo-radio-hydrogel implants may potentially improve the local control and overall outcome of aggressive, poor prognosis brain tumors.

Macrophages as nanoparticle delivery vectors for photothermal therapy of brain tumors

Certain types of stem and immune cells, which have an innate ability to target and infiltrate tumors, can be utilized as vectors to deliver several types of anticancer agents. In particular monocytes have the advantage of carrying relatively large payloads of therapeutic nanomaterials, can be patient derived in large numbers and are able to actively infiltrate tumors despite many barriers often present in the microenvironment. Monocytes can selectively cross the compromised blood-brain barrier surrounding brain tumors and are known to actively migrate to hypoxic tumor regions. Of particular interest is the observation that, following near-infrared exposure of tumors containing gold-nanoshell-loaded macrophages, sufficient hyperthermia can be generated to suppress tumor growth. Collectively, these findings demonstrate the potential of monocytes as nanoparticle delivery vectors for several types of site specific light-based cancer therapies.

Increased sensitivity of glioma cells to 5-fluorocytosine following photo-chemical internalization enhanced nonviral transfection of the cytosine deaminase suicide gene

Despite advances in surgery, chemotherapy and radiotherapy, the outcomes of patients with GBM have not significantly improved. Tumor recurrence in the resection margins occurs in more than 80% of cases indicating aggressive treatment modalities, such as gene therapy are warranted. We have examined photochemical internalization (PCI) as a method for the non-viral transfection of the cytosine deaminase (CD) suicide gene into glioma cells. The CD gene encodes an enzyme that can convert the nontoxic antifungal agent, 5-fluorocytosine, into the chemotherapeutic drug, 5-fluorouracil. Multicell tumor spheroids derived from established rat and human glioma cell lines were used as in vitro tumor models. Plasmids containing either the CD gene alone or together with the uracil phosphoribosyl transferase (UPRT) gene combined with the gene carrier protamine sulfate were employed in all experiments.PCI was performed with the photosensitizer AlPcS2a and 670 nm laser irradiance. Protamine sulfate/CD DNA polyplexes proved nontoxic but inefficient transfection agents due to endosomal entrapment. In contrast, PCI mediated CD gene transfection resulted in a significant inhibition of spheroid growth in the presence of, but not in the absence of, 5-FC. Repetitive PCI induced transfection was more efficient at low CD plasmid concentration than single treatment. The results clearly indicate that AlPcS2a-mediated PCI can be used to enhance transfection of a tumor suicide gene such as CD, in malignant glioma cells and cells transfected with both the CD and UPRT genes had a pronounced bystander effect.

Photochemical internalization of bleomycin for glioma treatment

We study the use of photochemical internalization (PCI) for enhancing chemotherapeutic response to malignant glioma cells in vitro. Two models are studied: monolayers consisting of F98 rat glioma cells and human glioma spheroids established from biopsy-derived glioma cells. In both cases, the cytotoxicity of aluminum phthalocyanine disulfonate (AlPcS2a)-based PCI of bleomycin was compared to AlPcS(2a)-photodynamic therapy (PDT) and chemotherapy alone. Monolayers and spheroids were incubated with AlPcS(2a) (PDT effect), bleomycin (chemotherapy effect), or AlPcS(2a)+bleomycin (PCI effect) and were illuminated (670 nm). Toxicity was evaluated using colony formation assays or spheroid growth kinetics. F98 cells in monolayer/spheroids were not particularly sensitive to the effects of low radiant exposure (1.5  J/cm(2) @ 5 mW/cm(2)) AlPcS(2a)-PDT. Bleomycin was moderately toxic to F98 cells in monolayer at relatively low concentrations-incubation of F98 cells in 0.1 μg/ml for 4 h resulted in 80% survival, but less toxic in human glioma spheroids respectively. In both in vitro systems investigated, a significant PCI effect is seen. PCI using 1.5 J/cm(2) together with 0.25 μg/ml bleomycin resulted in approximately 20% and 18% survival of F98 rat glioma cells and human glioma spheroids, respectively. These results show that AlPcS(2a)-mediated PCI can be used to enhance the efficacy of chemotherapeutic agents such as bleomycin in malignant gliomas.

Controversies concerning the application of brachytherapy in central nervous system tumors

INTRODUCTION

Brachytherapy (BRT) is defined as a therapy technique where a radioactive source is placed a short distance from or within the tumor being treated. Much expectation has been placed on its efficacy to improve the outcome for patients with central nervous system (CNS) tumors due to the initial promising results from single institution retrospective studies. However, these optimistic findings have been highly debated since the selection criteria itself is preferable to other therapeutic modalities. The fact that BRT demonstrated no significant survival advantage in two prospective studies, together with the emerging role of stereotactic convergence therapy as a promising alternative, has further decreased the enthusiasm for BRT. Despite all the negative aspects, BRT continues to be conducted for the management of CNS tumors including gliomas, meningiomas and brain metastases.

MATERIAL AND METHODS

As many controversies have been aroused concerning the experience and future application of BRT, this article reviews the existing heterogeneities in terms of implants choice, optimal dose rate, targeting volume, timing of BRT, patients selection, substantial efficacy, BRT in comparison with stereotactic convergence therapy techniques and BRT in combination with other treatment modalities (data were identified by Pubmed searches).

RESULTS AND CONCLUSION

Though it is inconvincible to argue for the routine use of BRT, BRT may provide a choice for patients with large recurrent or inoperable deep-seated tumors, especially with the Glia-site technique. Radiotherapies including BRT may hold more promise if biologic mechanisms of radiation could be better understand and biologic modifications could be added in clinical trials.

An estimation of radiobiologic parameters from clinical outcomes for radiation treatment planning of brain tumor

PURPOSE

To estimate a plausible set of radiobiologic parameters such as alpha, alpha/beta values, from clinical outcomes for biologically based radiation treatment planning of brain tumors.

METHODS AND MATERIALS

Linear-quadratic (LQ) formalism and the concept of equivalent uniform dose were used to analyze a series of published clinical data for malignant gliomas involving different forms of radiation therapy.

RESULTS

A plausible set of LQ parameters was obtained for gliomas: alpha = 0.06 +/- 0.05 Gy(-1), alpha/beta = 10.0 +/- 15.1 Gy, the tumor cell doubling time T(d) = 50 +/- 30 days, with the repair half-time of 0.5 h. The present estimated biologic parameters can reasonably predict the effectiveness of most of the recently reported clinical results employing either single or combined radiation therapy modalities. Different LQ parameters between Grade 3 and Grade 4 astrocytomas were found, implying the radiosensitivity for different grade tumors may be different. Smaller alpha, beta from in vivo was observed, indicating lower radiosensitivity occurred in vivo as compared with in vitro.

CONCLUSIONS

A plausible set of radiobiologic parameters for gliomas was estimated based on clinical data. These parameters can reasonably predict most of the clinical results. They may be used to design new treatment fractionation schemes and to evaluate and optimize treatment plans.

Influence of light fluence rate on the effects of photodynamic therapy in an orthotopic rat glioma model

OBJECT

Failure of treatment for high-grade gliomas is usually due to local recurrence at the site of resection, indicating that a more aggressive local therapy could be beneficial. Photodynamic therapy (PDT) is a local treatment involving the administration of a tumor-localizing photosensitizing drug, in this case aminolevulinic acid (ALA). The effect depends on the total light energy delivered to the target tissue, but may also be influenced by the rate of light delivery.

METHODS

In vitro experiments showed that the sensitivity to ALA PDT of BT4C multicellular tumor spheroids depended on the rate of light delivery (fluence rate). The BT4C tumors were established intracranially in BD-IX rats. Microfluorometry of frozen tissue sections showed that photosensitization is produced with better than 200:1 tumor/normal tissue selectivity after ALA injection. Four hours after intraperitoneal ALA injection (125 mg/kg), 26 J of 632 nm light was delivered interstitially over 15 (high fluence rate) or 90 (low fluence rate) minutes. Histological examination of animals treated 14 days after tumor induction demonstrated extensive tumor necrosis after low-fluence-rate PDT, but hardly any necrosis after high-fluence-rate treatment. Neutrophil infiltration in tumor tissue was increased by PDT, but was similar for both treatment regimens. Low-fluence-rate PDT administered 9 days after tumor induction resulted in statistically significant prolongation of survival for treated rats compared with nontreated control animals.

CONCLUSIONS

Treatment with ALA PDT induced pronounced necrosis in tumors only if the light was delivered at a low rate. The treatment prolonged the survival for tumor-bearing animals.

Photodynamic therapy of newly implanted glioma cells in the rat brain

BACKGROUND AND OBJECTIVE

A syngeneic rat brain tumor model is used to investigate the effects of aminolevulinic acid (ALA)-mediated photodynamic therapy (PDT) on small clusters of tumor cells sequestered in normal brain.

STUDY DESIGN/MATERIALS AND METHODS

Biodistribution studies on tumor-bearing animals were undertaken in order to determine the occurrence of photosensitizer in tumor cells invading normal brain. ALA-PDT toxicity in normal brain and gross tumor were evaluated from histopathology. Effects of PDT on isolated glioma cells in normal brain were investigated by treating animals 48 hours after tumor cell implantation.

RESULTS

Fluorescence microscopy of frozen tissue sections showed that photosensitizer content was limited and variable in tumor tissue invading normal brain. ALA-PDT with high light doses resulted in significant damage to both gross tumor and normal brain, however, the treatment failed to prolong survival of animals with newly implanted glioma cells. In contrast, animals inoculated with tumor cells pre-incubated in vitro with ALA showed a significant survival advantage in response to PDT.

CONCLUSION

The results show that ALA-PDT could not prevent tumors from forming if treatment was performed shortly after tumor initiation. This was likely due to inadequate levels of ALA/PpIX in the glioma cells.

Brachytherapy for brain tumors

Over the past several decades neurooncologists have attempted to find an adjuvant treatment that prolongs survival for patients with malignant brain tumors. Brachytherapy, radiotherapy delivered by placing radioactive sources directly into the tumor, was initially thought to be the solution to this problem. Initial single institution studies showed very promising results; however, this technique has failed to show a significant survival advantage in two randomized studies. Despite this, brachytherapy continues to be used in a number of centers throughout the world for the treatment of various types of brain tumors including low-grade gliomas, anaplastic astrocytomas, glioblastomas, meningiomas and metastases. This article reviews brachytherapy's rationale, radiobiology, complications, indications, and results from numerous studies that have focused on its application for brain tumors with emphasis on its application for glial tumors.

Enhanced cytotoxic effects of 5-aminolevulinic acid-mediated photodynamic therapy by concurrent hyperthermia in glioma spheroids

During photodynamic therapy (PDT) both normal and pathological brain tissue, in close proximity to the light source, can experience significant temperature increases. The purpose of this study was to investigate the anti-tumor effects of concurrent 5-aminolevulinic acid (ALA)-mediated PDT and hyperthermia (HT) in human and rat glioma spheroids. Human or rat glioma spheroids were subjected to PDT, HT, or a combination of the two treatments. Therapies were given concurrently to simulate the conditions that will occur during patient PDT. Predictions of diffusion theory suggest that brain tissue immediately adjacent to a spherical light applicator may experience temperature increases approaching 8 degrees C for laser input powers of 2 W. In the in vitro model employed here, HT had no effect on spheroid survival at temperatures below 49 degrees C, while sub-threshold fluence PDT results in only modest decrease in survival. HT (40-46 degrees C) and PDT interact in a synergistic manner if the two treatments are given concurrently. The degree of synergism increases with increasing temperature and light fluence. Apoptosis is the primary mode of cell death following both low-fluence rate PDT and combined HT + PDT.

Does imprint cytology of brain tumours improve intraoperative diagnoses?

OBJECTIVES

To evaluate the diagnostic accuracy using frozen sections only and a combination of imprint cytology and frozen sections.

MATERIAL AND METHODS

After introduction of imprint cytology as a supplement to frozen sections in 1999, 153 patients with brain tumours underwent stereotactic or open surgery. An equal number of cases prior to 1999 were chosen for comparison. Intraoperative diagnoses were compared with final diagnoses based on paraffin sections of the same tissue samples. The number of delayed intraoperative diagnoses was noted in each patient group.

RESULTS

The combined use of the two techniques improved intraoperative diagnostic accuracy from 87 to 91% while the delayed intraoperative diagnoses were significantly reduced from 30 to 8. The choice of surgical procedure did not affect the outcome of the pathological investigations.

CONCLUSION

A combination of frozen sections and imprints significantly reduced the number of delayed intraoperative diagnoses. Intraoperative diagnostic accuracy was improved, although not to a statistically significant level. Choice of surgical procedure did not affect the diagnostic outcome.

Neurosurgery at the University Hospital of North Norway: the history of the northernmost neurosurgical department in the world

The university hospital of North Norway hosts the northernmost neurosurgical department in the world. The hospital is located in the city of Tromsø, often dubbed "the Gateway to the Arctic." We describe the role of this city in polar exploration, the history preceding the establishment of the world's northernmost university, the history of neurosurgery at this institution, and the present state of the Department of Neurosurgery. The experience from Tromsø shows that it is possible to establish a complete neurosurgical service at remote locations. Training of physicians native to the region, close integration between clinical activities and research, and a wide definition of the specialty has been essential for the success of the department.

An inflatable balloon catheter and liquid 125I radiation source (GliaSite Radiation Therapy System) for treatment of recurrent malignant glioma: multicenter safety and feasibility trial

OBJECT

In this study the authors evaluated the safety and performance of the GliaSite Radiation Therapy System (RTS) in patients with recurrent malignant brain tumors who were undergoing tumor resection.

METHODS

The GliaSite is an inflatable balloon catheter that is placed in the resection cavity at the time of tumor debulking. Low-dose-rate radiation is delivered with an aqueous solution of organically bound iodine-125 (lotrex [sodium 3-(125I)-iodo-4-hydroxybenzenesulfonate]), which are temporarily introduced into the balloon portion of the device via a subcutaneous port. Adults with recurrent malignant glioma underwent resection and GliaSite implantation. One to 2 weeks later, the device was filled with Iotrex for 3 to 6 days, following which the device was explanted. Twenty-one patients with recurrent high-grade astrocytomas were enrolled in the study and received radiation therapy. There were two end points: 1) successful implantation and delivery of brachytherapy; and 2) safety of the device. Implantation of the device, delivery of radiation, and the explantation procedure were well tolerated. At least 40 to 60 Gy was delivered to all tissues within the target volume. There were no serious adverse device-related events during brachytherapy. One patient had a pseudomeningocele, one patient had a wound infection, and three patients had meningitis (one bacterial, one chemical, and one aseptic). No symptomatic radiation necrosis was identified during 21.8 patient-years of follow up. The median survival of previously treated patients was 12.7 months (95% confidence interval 6.9-15.3 months).

CONCLUSIONS

The GliaSite RTS performs safely and efficiently. It delivers a readily quantifiable dose of radiation to tissue at the highest risk for tumor recurrence.

High-dose-rate stereotactic brachytherapy for patients with newly diagnosed glioblastoma multiformes

PURPOSE

To evaluate high-dose-rate (HDR) stereotactic brachytherapy (STBT) for glioblastoma multiforme (GBM).

MATERIALS AND METHODS

Between August 1994 and December 1998, 28 patients with newly diagnosed GBM underwent surgery, external-beam radiotherapy (EBRT) and HDR STBT. STBT eligibility criteria included unifocal lesions, residual tumor < or = 6 cm in maximum diameter, supratentorial lesions, tumors not crossing the midline, tumors without subependymal spread and Karnofsky performance status (KPS) > 60. STBT was delivered over five consecutive days with two fractions per day for a total median dose of 30 Gy. Twenty-eight STBT eligible GBM patients treated with surgery and EBRT only over the same period were matched controls.

RESULTS

Median survival times for the STBT group and controls were 19.5 versus 12.5 months; one and two year survival rates were 89% versus 42% and 61% versus 28%, respectively (p = 0.12). Using multivariate analysis, age, KPS and HDR STBT were significant factors predicting survival. By RPA class, 2-year survival rates for STBT and controls were: III--78% versus 50%; IV--40% versus 0%; V--21% versus 15%, respectively. Corresponding median survival times in months were: 41.6 versus 21.2 (p = 0.39); 16.7 versus 12.1 (p = 0.36); 18.7 versus 10.6 (p = 0.02). No major complications were found in the STBT arm.

CONCLUSIONS

Because of small patient numbers, median survival time increases were only statistically significant in the RPA Class V patients, but a strong survival time trend emerged favoring patients undergoing HDR STBT. Further prospective study is warranted to fully assess the merits of this technique for GBM management.

Effects of combined photodynamic therapy and ionizing radiation on human glioma spheroids

The effects of combined photodynamic therapy (PDT) and ionizing radiation are studied in a human glioma spheroid model. The degree of interaction between the two modalities depends in a complex manner on factors such as PDT irradiation fluence, fluence rate and dose of ionizing radiation. It is shown that gamma radiation and PDT interact in a synergistic manner only if both light fluence and gamma radiation dose exceed approximately 25 J cm(-2) and 8 Gy, respectively. Synergistic interactions are observed only for the lower fluence rate (25 mW cm(-2)) investigated. The degree of interaction appears to be independent of both sequence and the PDT or ionizing radiation time intervals investigated (1 and 24 h). Terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling assays show that low-fluence rate PDT is very efficient at inducing apoptotic cell death, whereas neither high-fluence rate PDT nor ionizing radiation produces significant apoptosis. Although the mechanisms remain to be elucidated, the data imply that the observed synergism is likely not due to gamma-induced cell cycle arrest or to PDT-induced inhibition of DNA repair.

Development of a novel indwelling balloon applicator for optimizing light delivery in photodynamic therapy

BACKGROUND AND OBJECTIVE

A human glioma spheroid model is used to investigate the efficacy of different light delivery schemes in 5-aminolevulinic acid (ALA)--mediated photodynamic therapy (PDT). The results provide the rationale for the development of an indwelling balloon applicator for optimizing light delivery.

STUDY DESIGN/MATERIALS AND METHODS

Human glioma spheroids were incubated in ALA (100 or 1000 microg /ml-1) for 4 hours and subjected to various light irradiation schemes. In one set of experiments, spheroid survival was monitored as a function of light fluence rate (5-200 mW cm-2). In all cases, spheroids were exposed to fluences of either 25 or 50 J cm-2. In a second study, the effects of repeated weekly PDT treatments, using sub-threshold fluences, were investigated. One group of spheroids was subjected to three treatments using fluences of 12, 12, and 25 J cm-2. Results were compared to spheroids receiving single treatments of either 12 or 25 J cm-2. A fluence rate of 25 mW cm-2 was used for all three groups of spheroids. In all cases, the effect of a given irradiation scheme was evaluated by monitoring spheroid growth.

RESULTS

Low fluence rates produce greater cell kill than high fluence rates. The minimum effective fluence rate in human glioma spheroids is approximately 10 mW cm-2. Repeated weekly PDT treatments with sub-threshold fluences result in significant cell kill. In spheroids surviving the PDT treatments, growth is suppressed for the duration of the treatment period.

CONCLUSION

The results of the in vitro studies support the development of an indwelling balloon applicator for the delivery of light doses in long term multi-fractionated PDT regimens.

ALA- and ALA-ester-mediated photodynamic therapy of human glioma spheroids

The effects of photodynamic therapy (PDT) in human glioma spheroids incubated in 5-aminolevulinic acid (ALA), or ALA esters, are investigated. Spheroid survival and growth are monitored following PDT at representative drug concentrations, light doses, and dose rates. The primary finding of this study is that the response of human glioma spheroids to PDT with lipophilic ester derivatives, such as benzyl-ALA and hexyl-ALA, is equivalent to that observed with ALA, however, this equivalency is obtained for ester concentrations 10-20 times lower than the parent compound. The enhanced efficiency of the esters is likely due to their increased membrane penetrance. Potential clinical advantages of using lipophilic esters in PDT of gliomas are discussed.

Preclinical evaluation of a novel device for delivering brachytherapy to the margins of resected brain tumor cavities

OBJECT

The objectives of this study were to evaluate the safety and performance of a new brachytherapy applicator in the treatment of resected brain tumors in a canine model.

METHODS

The brachytherapy applicator is an inflatable balloon catheter that is implanted in the resection cavity remaining after a brain tumor has been debulked. After implantation the balloon is inflated with Iotrex, a sterile solution containing organically bound iodine-125. The low-energy photons emitted by the iodine-125 deposit a therapeutic radiation dose across short distances from the surface of the balloon. After delivery of a prescribed radiation dose to the targeted volume, the radioactive fluid is retrieved and the catheter removed. Small resections of the right frontal lobe were performed in large dogs. Magnetic resonance (MR) images were obtained and used to assess tissue response and to measure the conformance between the resection cavity wall and the balloon surface. In four animals a dose ranging from 36 to 59 Gy was delivered. Neurological status and histological characteristics of the brain were assessed in all dogs. Implantation and explantation as well as inflation and deflation of the device were easily accomplished and well tolerated. The device was easily visualized on MR images, which demonstrated the expected postsurgical changes. The resection cavity and the balloon were highly conformal (range 93-100%). Histological changes to the cavity margin were consistent with those associated with surgical trauma. Additionally, radiation-related changes were observed at the margins of the resection cavity in dogs in which the brain was irradiated.

CONCLUSIONS

This balloon catheter and 125I radiotherapy solution system can safely and reliably deliver radiation to the margins of brain cavities created by tumor resection. Results of this study showed that intracranial pressure changes due to balloon inflation and deflation were unremarkable and characteristic of the imaging properties and radiation safety profile of the device prior to its clinical evaluation. Clinically relevant brachytherapy (adequate target volume and total dose) was accomplished in all four animals subjected to treatment.

A cost-minimising analysis of standard radiotherapy and two experimental therapies in glioblastoma

BACKGROUND AND PURPOSE

Accelerated radiotherapy (ART) and intracavity brachytherapy (ICBT) have been introduced in the primary treatment of glioblastoma. Our objective was to determine total treatment costs, hospitalisation time, and treatment outcome in these two experimental therapies compared to standard treatment.

MATERIALS AND METHODS

In the time period 1985 to 1st May 1999, a total of 174 patients with histologically confirmed glioblastoma multiforme were given postoperative radiotherapy according to three different treatment schedules at three different time intervals. A conventional regime of external radiotherapy (54Gy/30 fractions) was given to 58 patients (group I), 75 patients were treated with ART (48Gy/twice daily 30 fractions) (group II), and 41 patients were given ICBT (60Gy/ten fractions) (group III). Treatment costs including surgery, hospital stay, hospital hotel stay, and radiotherapy were calculated.

RESULTS

The total mean costs employing the three treatment alternatives were calculated to $25,618 (group I), $23,442 (group II), and $14,534 (group III). Total mean stay in hospital for the whole primary treatment was 48.8, 41.6, and 19 days for groups I, II, and III respectively. Median survival figures were 16, 14, and 13 months for groups I, II, and III, respectively.

CONCLUSIONS

The total cost of postoperative radiotherapy in glioblastoma is comparable to other health care services. ART did not improve the total treatment cost or influence the need for hospitalisation compared to standard treatment. ICBT seemed to have economic benefits with less need for hospitalisation.

Neurosurgical advances in the treatment of brain tumors

Surgery remains an important part of the treatment of primary malignant brain tumors. When surgery is utilized, care must be taken to maximize the safety of the procedures. This article emphasizes advances in lesion localization within the brain and technology used to identify the function of normal tissue around the tumor. Many of the new treatment paradigms involve a surgical procedure. For example, surgery is necessary for biodegradable treatment delivery systems, and for some focal radiation therapy. Neurosurgeons are familiar with implantable catheter systems for other types of disease such as hydrocephalus; however, there is now an opportunity to take advantage of such technology to assist in the delivery of treatment agents locally within a tumor. Although no specific surgical advance has offered cure of malignant tumors, surgery remains necessary for utilization of the treatment advances now becoming available.