Functional and histological damage in the mouse bladder after photodynamic therapy

Advances in Management of Bladder Cancer-The Role of Photodynamic Therapy

Photodynamic therapy (PDT) is a non-invasive and modern form of therapy. It is used in the treatment of non-oncological diseases and more and more often in the treatment of various types of neoplasms in various locations including bladder cancer. The PDT method consists of local or systemic application of a photosensitizer, i.e., a photosensitive compound that accumulates in pathological tissue. Light of appropriate wavelength is absorbed by the photosensitizer molecules, which in turn transfers energy to oxygen or initiates radical processes that leads to selective destruction of diseased cells. The technique enables the selective destruction of malignant cells, as the photocytotoxicity reactions induced by the photosensitizer take place strictly within the pathological tissue. PDT is known to be well tolerated in a clinical setting in patients. In cited papers herein no new safety issues were identified. The development of anti-cancer PDT therapies has greatly accelerated over the last decade. There was no evidence of increased or cumulative toxic effects with each PDT treatment. Many modifications have been made to enhance the effects. Clinically, bladder cancer remains one of the deadliest urological diseases of the urinary system. The subject of this review is the anti-cancer use of PDT, its benefits and possible modifications that may lead to more effective treatments for bladder cancer. Bladder cancer, if localized, would seem to be a good candidate for PDT therapy since this does not involve the toxicity of systemic chemotherapy and can spare normal tissues from damage if properly carried out. It is clear that PDT deserves more investment in clinical research, especially for plant-based photosensitizers. Natural PS isolated from plants and other biological sources can be considered a green approach to PDT in cancer therapy. Currently, PDT is widely used in the treatment of skin cancer, but numerous studies show the advantages of related therapeutic strategies that can help eliminate various types of cancer, including bladder cancer. PDT for bladder cancer in which photosensitizer is locally activated and generates cytotoxic reactive oxygen species and causing cell death, is a modern treatment. Moreover, PDT is an innovative technique in oncologic urology.

On the Development of a Light Dosimetry Planning Tool for Photodynamic Therapy in Arbitrary Shaped Cavities: Initial Results

Previous dosimetric studies during photodynamic therapy (PDT) of superficial lesions within a cavity such as the nasopharynx, demonstrated significant intra- and interpatient variations in fluence rate build-up as a result of tissue surface re-emitted and reflected photons, which depends on the optical properties. This scattering effect affects the response to PDT. Recently, a meta-tetra(hydroxyphenyl)chlorin-mediated PDT study of malignancies in the paranasal sinuses after salvage surgery was initiated. These geometries are complex in shape, with spatially varying optical properties. Therefore, preplanning and in vivo dosimetry is required to ensure an effective fluence delivered to the tumor. For this purpose, two 3D light distribution models were developed: first, a simple empirical model that directly calculates the fluence rate at the cavity surface using a simple linear function that includes the scatter contribution as function of the light source to surface distance. And second, an analytical model based on Lambert's cosine law assuming a global diffuse reflectance constant. The models were evaluated by means of three 3D printed optical phantoms and one porcine tissue phantom. Predictive fluence rate distributions of both models are within ± 20% accurate and have the potential to determine the optimal source location and light source output power settings.

Assessment of photosensitizer dosimetry and tissue damage assay for photodynamic therapy in advanced-stage tumors

Photodynamic therapy (PDT) efficacy is a complex function of tissue sensitivity, photosensitizer (PS) uptake, tissue oxygen concentration, delivered light dose and some other parameters. To better understand the mechanisms and optimization of PDT treatment, we assessed two techniques for quantifying tissue PS concentration and two methods for quantifying pathological tumor damage. The two methods used to determine tissue PS concentration kinetic were in vivo fluorescence probe and ex vivo chemical extraction. Both methods show that the highest tumor to normal tissue PS uptake ratio appears 4 h after PS administration. Two different histopathologic techniques were used to quantify tumor and normal tissue damage. A planimetry assessment of regional tumor necrosis demonstrated a linear relationship with increasing light dose. However, in large murine tumors this finding was complicated by the presence of significant spontaneous necrosis. A second method (densitometry) assessed cell death by nuclear size and density. With some exceptions the densitometry method generally supported the planimetry results. Although the densitometry method is potentially more accurate, it has greater potential subjectivity. Finally, our research suggests that the tools or methods we are studying for quantifying PS levels and tissue damage are necessary for the understanding of PDT effect and therapeutic ratio in experimental in vivo tumor research.

Whole bladder photodynamic therapy for orthotopic superficial bladder cancer in rats: a study of intravenous and intravesical administration of photosensitizers

PURPOSE

Photodynamic therapy after intravenous injection of Photofrin (QLT Phototherapeutics, Vancouver, British Columbia, Canada) results in a contracted bladder and skin photosensitivity, which limits its clinical application. In an attempt to overcome these limitations photodynamic therapy after intravesical instillation of Photofrin or 5-aminolevulinic acid (ALA) in an orthotopic rat bladder tumor model was explored and compared with intravenous Photofrin for photodynamic therapy efficacy and phototoxicity.

MATERIALS AND METHODS

At 2 weeks after bladder implantation of 1.5 x 10(6) AY-27 tumor cells animals were randomly grouped. Photofrin was administered (5 mg./kg. intravenously and 2 mg./ml. intravesically). The ALA concentration for intravesical instillation was 300 mM. Whole bladder photodynamic therapy with graded doses of light (lambda = 630 nm.) was performed 4 hours after drug administration. Tumor control and complications were evaluated.

RESULTS

Photodynamic therapy with intravenous Photofrin plus 100 J./cm.(2) light resulted in severe bladder damage. Of 10 rats 6 died and 2 of the 10 that received 50 J./cm.(2) died. There were no photodynamic therapy related deaths in groups receiving intravesical instillation of Photofrin or ALA that also received 50 to 100 J./cm.(2) Median survival in rats treated with ALA intravesically plus 75 J./cm.(2) (77 days), Photofrin intravesically plus 50 (67) or 100 J./cm.(2) (76) and Photofrin intravenously plus 50 J./cm.(2) (60) were significantly different from that in controls (44).

CONCLUSIONS

Intravesical instillation of Photofrin or ALA can achieve the same photodynamic therapy efficacy as intravenous Photofrin in this orthotopic rat bladder tumor model with less phototoxicity to normal tissues.

Optimization of differential photodynamic effectiveness between normal and tumor urothelial cells using 5-aminolevulinic acid-induced protoporphyrin IX as sensitizer

Photodynamic therapy using 5-aminolevulinic acid (5-ALA)-induced protoporphyrin IX is a promising tool in bladder-cancer therapy. However, little is known about the cellular mechanisms of phototoxicity. Our aim was to characterize the cellular damage and to optimize differential photodynamic effectiveness between tumor and normal urothelial cells. RT4 tumor and UROtsa normal urothelial cells were used to simulate a papillary bladder tumor in contrast to normal urothelium. Photodynamically induced damage in plasma membrane and mitochondria was monitored by flow cytometry with propidium iodide exclusion and analysis of aggregate formation of the dye JC-1. Cell morphology was investigated by phase-contrast and fluorescence microscopy following acridine orange staining. Long incubation times (3 hr) led to complete RT4 tumor cell kill accompanied by a marked fraction of damaged normal UROtsa cells. Shorter incubation intervals (1 hr) also resulted in complete RT4 tumor cell kill; however, most UROtsa cells retained their cell properties, including intact plasma membrane and active mitochondria as well as intact cellular morphology. Phototoxicity depends not only on cellular sensitizer accumulation but also on intracellular localization. Analysis of phototoxic mechanisms is an important step for planning combination therapy regimens with, e.g., DNA-damaging agents. Further, data indicate that differential phototoxicity in normal and tumorous urothelium can be enhanced using differences in cellular protoporphyrin IX distribution following short 5-ALA incubation times. These data are encouraging for the in vivo situation since short incubation times are a more practical approach for local photodynamic therapy of early tumor stages not only in the bladder but also, e.g., in the gastro-intestinal tract or bronchial mucosa.

Photodynamic therapy of rat bladder and urethra: evaluation of urinary and reproductive function after inducing protoporphyrin IX with 5-aminolaevulinic acid

OBJECTIVE

To assess the urinary and reproductive function of rats after inducing protoporphyrin IX with 5-aminolaevulinic acid (ALA) and subsequent intraurethral photodynamic therapy (PDT). Materials and methods Twelve female Wistar rats were given ALA orally or intravesically (four each), followed by intraurethral PDT through a 10-mm cylindrical fibre at 100 mW for 500 s (argon laser, 632 nm). Urinary frequency, the number of gestations and histological changes were then evaluated and compared with a group of eight control rats.

RESULTS

There was only a slight increase in urinary frequency during the first 2 weeks after PDT in the group given oral ALA, while the same degree of urinary frequency was evident for up to 4 weeks in those given intravesical ALA. Despite the occurrence of urinary incontinence from undefined causes in two rats, reproductive function remained unchanged. There was no histological evidence of damage to the reproductive system adjacent to the bladder.

CONCLUSIONS

PDT of the urethra with ALA is relatively safe and carries few risks of inducing permanent urological complications.

A comparison of functional bladder damage after intravesical photodynamic therapy with three different photosensitizers

The influence of type of photosensitizer, drug and light dose, and time interval between photosensitizer and illumination on the extent of photodynamic therapy (PDT)-induced bladder damage and recovery was investigated using a mouse model. The three photosensitizers studied were Photofrin, meso-tetrahydroxyphenylchlorin (m-THPC) and bacteriochlorin a (BCA). Functional bladder damage was quantitatively assessed from increases in urination frequency index (FI) at 1-35 weeks after illumination and histological damage was qualitatively assessed at 1 day, 1, 2 and 12 weeks. Photofrin-mediated PDT caused an acute increase in FI at 1 week, with recovery within 2-8 weeks after light doses of 2.7-8.2 J/cm2. After higher light doses there was only partial recovery. Previous results indicated that the acute response and rate of recovery was the same whether Photofrin was given at 1 day or up to 7 days before illumination. The m-THPC-mediated PDT at drug doses of > or = 0.3 mg/kg also resulted in a marked acute response with good recovery, even after 10.8 J/cm2. Lower drug doses in combination with 5.4 J/cm2 did not result in acute or late damage. There was no significant difference in acute response when m-THPC was given 1, 3 or 7 days before illumination, although recovery was faster for the longer illumination intervals (3 or 7 days). Illumination at 1 h after 20 mg/kg BCA induced an acute response within 2 days after illumination, with recovery within 4-8 weeks. Lower drug doses did not result in damage. The most prominent histological changes during the acute period with all three photosensitizers were submucosal edema and vessel dilation, with epithelial denudation (depending on drug/light dose). We conclude that BCA and m-THPC are both potent new photosensitizers. They can induce a moderate to severe acute bladder response with complete healing over a period of a few weeks. The photosensitizer m-THPC is very effective with low doses of photosensitizer and light, whereas relatively high doses of BCA and light are required to obtain equivalent functional bladder damage in our mouse model.

The influence of intravesical photodynamic therapy on subsequent bladder irradiation tolerance

The aim of this project was to measure the irradiation tolerance of normal (non tumour bearing) mouse bladder after previous intravesical photodynamic therapy (PDT). Illumination with a range of light doses at 24 h after Photofrin was used as the initial PDT treatment and irradiation with a range of X-ray doses was given at 12 or 24 weeks after the initial therapy. Functional bladder damage was assessed from changes in micturition frequency (tested regularly for a follow-up period of 53 weeks after irradiation) and from cystometry measurements of the bladder at 53-56 weeks. PDT alone caused a marked increase in micturition frequency, with (partial) recovery by the time of irradiation. Irradiation alone caused a modest, transient acute response within 5 weeks and a progressive, permanent late response starting from about 25 weeks depending on X-ray dose. A reduced bladder capacity was also evident at 53-56 weeks after 20 Gy X-rays and after PDT alone. Irradiation after previous intravesical PDT caused an acute reaction similar to X-rays alone, but there was a much earlier expression of late functional bladder damage. The final level of damage prior to sacrifice at 53-56 weeks, was not significantly greater than after X-rays alone. These results suggest that irradiation after previous whole bladder PDT, for refractory bladder tumours, may lead to an increased risk of persistent increases in micturition frequency and reduced bladder capacity, beginning at very early times after irradiation.

Intraperitoneal photodynamic therapy in the rat: comparison of toxicity profiles for photofrin and MTHPC

Toxicity studies for intraperitoneal photodynamic therapy (IPPDT) were performed in Wag/RijA rats, using specially designed light delivery blocks for proper light distribution and light dosimetry. A recently developed photosensitizer mesotetrahydroxyphenylchlorin (mTHPC), excited at 652-nm wave-length, was compared with Photofrin (630 nm). Toxicity profiles for various sensitizer doses, light fluences and time intervals were investigated. A light fluence of 15 J.cm-2 delivered to the entire peritoneum 24 hr after 5 mg Photofrin per kg i.v. induced reversible impairment of intestinal, liver and kidney function. A dose of 0.2 mg mTHPC per kg i.v. followed by 6 J.cm-2 at 72 hr appeared to be equitoxic to the intestines; however, functional tests revealed little effect for this mTHPC-mediated IPPDT regime on liver or kidney. Histology demonstrated focal irreversible damage to the kidneys for both photosensitizers, not reflected in functional impairment. Light doses of 25 to 30 J.cm-2 at 24 hr after Photofrin or 8-12 J.cm-2, 72 hr after mTHPC caused lethal toxicity in the first 2 weeks due to intestinal damage. Higher light doses caused a shock syndrome and rhabdomyolysis resulting in death within 20 hr for both photosensitizers. In conclusion, maximum tolerable schedules for whole-abdomen IPPDT were defined for Photofrin and mTHPC. Both photosensitizers caused similar toxicity profiles depending on drug dose, light fluence and time interval.

Functional and histological bladder damage in mice after photodynamic therapy: the influence of sensitiser dose and time of administration

The bladders of anaesthetised mice were illuminated with red laser light (630 nm) at intervals of 1 day to 4 weeks after i.p. administration of Photofrin. Light was delivered intravesically by inserting a fibre optic, with a diffusing bulb tip, into the centre of fluid filled bladders. A single light dose of 11.3 J cm-2 applies 1 day after 10 mg kg-1 Photofrin caused a severe acute response, with increased urination frequency (five to seven times control) and hematuria. Recovery was good, however, and by 10 weeks only a mild (approximately two-fold) increase in frequency remained. There was no reduction in the amount of acute bladder damage or in the rate of healing when the interval between Photofrin and light was increased from 1 to 7 days but a 2 to 3 week interval lead to a significant reduction in damage. For an interval of 4 weeks there was only a mild (less than two-fold) increase in urination frequency during the first week. A drug dose of 2.5 mg kg-1 given 1 day before illumination caused transient haematuria but no increase in urination frequency. Doses of 5, 7.5 or 10 mg kg-1 all caused photosensitisation and the amount of bladder damage was drug dose dependent. The bladder seems to be well able to recover from severe acute damage induced by PDT. Occasional incidences of pyelonephritis were seen, however, suggesting that urinary tract infection during the acute period may lead to permanent renal damage.