In situ comparison of 665 nm and 633 nm wavelength light penetration in the human prostate gland

Development of a novel laboratory photodynamic therapy device: automated multi-mode LED system for optimum well-plate irradiation

Photodynamic therapy (PDT) is a targeted treatment method that utilizes a photosensitizer (PS) to induce cytotoxicity in malignant and non-malignant tumors. Optimization of PDT requires investigation of the selectivity of PS for the target tissues, irradiating light source, irradiation wavelengths, fluence rate, fluence, illumination mode, and overall treatment plan. In this study, we developed the Multi-mode Automatized Well-plate PDT LED Laboratory Irradiation System (MAWPLIS), an innovative device that automates time-consuming well plate light dosage/PS dose measurement experiment. The careful control of LED current and temperature stabilization in the LED module allowed the system to achieve high optical output stability. The MAWPLIS was designed by integrating a 3-axis moving system and motion controller, a quick-switching LED controller unit equipped with interchangeable LED modules capable of employing multiple wavelengths, and a TEC system. The proposed system achieved high optical output stability (1 mW) within the range of 0-500 mW, high wavelength stability (5 nm) at 635 nm, and high temperature stability (0.2 °C) across all radiation modes. The system's validation involved in vitro analysis using 5-ALA across varying concentrations, incubation periods, light exposures, and wavelengths in HT-29 colon cancer and WI-38 human lung fibroblast cell lines. Specifically, a combination of 405 nm and 635 nm wavelengths was selected to demonstrate enhanced strategies for colon cancer cell eradication and system validation. The MAWPLIS system represents a significant advancement in photodynamic therapy (PDT) research, offering automation and standardization of time-intensive experiments, high stability and precision, and improved PDT efficacy through dual-wavelength integration.

Zn phthalocyanines loaded into liposomes: Characterization and enhanced performance of photodynamic activity on glioblastoma cells

Photodynamic therapy (PDT) is considered a promising strategy for cancer treatment. PDT utilizes light in combination with a photosensitizer (PS) to induce several phototoxic reactions. Phthalocyanines (Pcs), a second generation of photosensitizers, have been studied in several cancer models. Among these, Pcs, have become of interest for the treatment of glioblastomas which are one of the most common and aggressive forms of tumors of the central nervous system. Due to the lipophilic nature of Pcs and their limited solubility in water, Pcs can be loaded in liposomes. In this work, we characterized liposomes of ZnPc and TAZnPc and their effectiveness to photoinactivate glioblastoma cells, was evaluated. Both Pcs show an increase in their photosensitizing activity when they were administrated in Dipalmitoylphosphatidylcholine-cholesterol liposomes compared to Pcs administrated in dimethylformamide.

Effectiveness of ZnPc and of an amine derivative to inactivate Glioblastoma cells by Photodynamic Therapy: an in vitro comparative study

Glioblastoma multiforme is considered to be one of the most aggressive types of tumors of the central nervous system, with a poor prognosis and short survival periods of ~ one year. The current protocol for glioblastoma treatment includes the surgical excision of the primary tumor followed by radio and chemotherapy. Photodynamic therapy (PDT) is considered a promising strategy for the treatment of several types of tumors. Phthalocyanines (Pcs) are good photosensitizers (PSs) for PDT because they induce cell death in several cellular models. ZnPc (Zn(II)phthalocyanine) is a well-known Pc, extensively tested in different cells and tumor models, but its evaluation on a glioblastoma model has been poorly studied. Herein, we compare the capacity of ZnPc and one of its derivatives, Zn(II)tetraminephthalocyanine (TAZnPc), to photoinactivate glioblastoma cells (T98G, MO59, LN229 and U87-MG) in culture. We measured the cellular uptake, the toxicity in the dark and the subcellular localization of the different Pcs, as well as the clonogenic capacity of surviving cells after PDT. The mechanism of cell death induced after PDT was determined by measuring caspase 3 activation, DNA fragmentation, phosphatidylserine externalization, mitochondrial morphological changes and loss of mitochondrial membrane potential as well as lysosomal membrane integrity. Overall, ZnPc and TAZnPc present good properties to be used as PSs with photoinactivation capacity on glioblastoma cells.

Chlorin e6-Coated Superparamagnetic Iron Oxide Nanoparticle (SPION) Nanoclusters as a Theranostic Agent for Dual-Mode Imaging and Photodynamic Therapy

Photodynamic therapy (PDT) is an approved modality for the treatment of various types of maligancies and diseased states. However, most of the available photosensitizers (PS) are highly hydrophobic, which limits their solubility and dispersion in biological fluids and can lead to self-quenching and sub-optimal therapeutic efficacy. In this study, chlorin e6 (Ce6)-coated superparamagnetic iron oxide nanoparticle (SPION) nanoclusters (Ce6-SCs) were prepared via an oil-in-water emulsion. The physical-chemical properties of the Ce6-SCs were systematically evaluated. Dual-mode imaging and PDT was subsequently performed in tumor-bearing mice. Chlorin e6 is capable of solubilizing hydrophobic SPION into stable, water-soluble nanoclusters without the use of any additional amphiphiles or carriers. The method is reproducible and the Ce6-SCs are highly stable under physiological conditions. The Ce6-SCs have an average diameter of 92 nm and low polydispersity (average PDI < 0.2). Encapsulation efficiency of both Ce6 and SPION is ≈100%, and the total Ce6 payload can be as high as 56% of the total weight (Ce6 + Fe). The Ce6-SCs localize within tumors via enhanced permeability and retention and are detectable by magnetic resonance (MR) and optical imaging. With PDT, Ce6-SCs demonstrate high singlet oxygen generation and produce a significant delay in tumor growth in mice.

Should open excisions and sutured incisions be treated differently? A review and meta-analysis of animal wound models following low-level laser therapy

Although low-level laser therapy (LLLT) was discovered already in the 1960s of the twentieth century, it took almost 40 years to be widely used in clinical dermatology/surgery. It has been demonstrated that LLLT is able to increase collagen production/wound stiffness and/or improve wound contraction. In this review, we investigated whether open and sutured wounds should be treated with different LLLT parameters. A PubMed search was performed to identify controlled studies with LLLT applied to wounded animals (sutured incisions-tensile strength measurement and open excisions-area measurement). Final score random effects meta-analyses were conducted. Nineteen studies were included. The overall result of the tensile strength analysis (eight studies) was significantly in favor of LLLT (SMD = 1.06, 95% CI 0.66-1.46), and better results were seen with 30-79 mW/cm² infrared laser (SMD = 1.44, 95% CI 0.67-2.21) and 139-281 mW/cm² red laser (SMD = 1.52, 95% CI 0.54-2.49). The overall result of the wound contraction analysis (11 studies) was significantly in favor of LLLT (SMD = 0.99, 95% CI 0.38-1.59), and the best results were seen with 53-300 mW/cm² infrared laser (SMD = 1.18, 95% CI 0.41-1.94) and 25-90 mW/cm² red laser (SMD = 1.6, 95% CI 0.27-2.93). Whereas 1-15 mW/cm² red laser had a moderately positive effect on sutured wounds, 2-4 mW/cm² red laser did not accelerate healing of open wounds. LLLT appears effective in the treatment of sutured and open wounds. Statistical heterogeneity indicates that the tensile strength development of sutured wounds is more dependent on laser power density compared to the contraction rate of open wounds.

Infrared laser pulse triggers increased singlet oxygen production in tumour cells

Photodynamic therapy (PDT) is a technique developed to treat the ever-increasing global incidence of cancer. This technique utilises singlet oxygen (¹O₂) generation via a laser excited photosensitiser (PS) to kill cancer cells. However, prolonged sensitivity to intensive light (6–8 weeks for lung cancer), relatively low tissue penetration by activating light (630 nm up to 4 mm), and the cost of PS administration can limit progressive PDT applications. The development of quantum-dot laser diodes emitting in the highest absorption region (1268 nm) of triplet oxygen (³O₂) presents the possibility of inducing apoptosis in tumour cells through direct ³O₂ → ¹O₂ transition. Here we demonstrate that a single laser pulse triggers dose-dependent ¹O₂ generation in both normal keratinocytes and tumour cells and show that tumour cells yield the highest ¹O₂ far beyond the initial laser pulse exposure. Our modelling and experimental results support the development of direct infrared (IR) laser-induced tumour treatment as a promising approach in tumour PDT.

Efficacy of 2-(1-hexyloxyethyl)-2-devinyl pyropheophorbide-a in photodynamic therapy of human esophageal squamous cancer cells

The present study investigated the effects of 2-(1-hexyloxyethyl)-2-devinylpyro pheophorbide-a (HPPH)-mediated photodynamic therapy (PDT) on in vitro cell survival and in vivo tumor growth derived from human esophageal squamous cancer cells (Eca109). A cell counting kit 8 (CCK8) assay was used to assess the phototoxicity of HPPH-mediated PDT in cultured Eca109 cells. The inhibition of tumor growth was determined by the changes in the relative tumor volume (RTV) and tumor weight. The results revealed that HPPH, in the range of 0.005-1 μg/ml, exhibited no cytotoxicity in the Eca109 cells without light exposure and that the in vitro efficiency of HPPH-mediated PDT was higher compared with that of Photofrin^®-mediated PDT. The in vivo results indicated that graded doses of HPPH-mediated PDT significantly inhibited the xenograft tumor growth derived from the Eca109 cells in a dose-dependent manner. The inhibition efficacy of 0.6 and 1.0 mg/kg HPPH-mediated PDT was similar to that of 10 mg/kg Photofrin-mediated PDT. Furthermore, HPPH possessed a lower toxicity than Photofrin at the dose that achieved the same efficacy in mice bearing Eca109 subcutaneous tumors. The histopathological findings indicated that the tumor tissues in the photosensitizer (PS)-treated mice demonstrated varying degrees of necrosis. HPPH and Photofrin exhibited vascular cytotoxicity on the treated tumors. In conclusion, the present study demonstrated that the phototoxicity of HPPH-mediated PDT is higher than that of Photofrin-mediated PDT of the same dose. HPPH possessed lower toxicity than Photofrin at the dose that achieved the same efficacy. Therefore, HPPH may be a promising agent for treating human esophageal squamous cell cancer (ESCC).

Determination of optical properties in heterogeneous turbid media using a cylindrical diffusing fiber

For interstitial photodynamic therapy (PDT), cylindrical diffusing fibers (CDFs) are often used to deliver light. This study examines the feasibility and accuracy of using CDFs to characterize the absorption (μ(a)) and reduced scattering (μ'(s)) coefficients of heterogeneous turbid media. Measurements were performed in tissue-simulating phantoms with μ(a) between 0.1 and 1 cm(-1) and μ'(s) between 3 and 10 cm(-1) with CDFs 2 to 4 cm in length. Optical properties were determined by fitting the measured light fluence rate profiles at a fixed distance from the CDF axis using a heterogeneous kernel model in which the cylindrical diffusing fiber is treated as a series of point sources. The resulting optical properties were compared with independent measurement using a point source method. In a homogenous medium, we are able to determine the absorption coefficient μ(a) using a value of μ'(s) determined a priori (uniform fit) or μ'(s) obtained by fitting (variable fit) with standard (maximum) deviations of 6% (18%) and 18% (44%), respectively. However, the CDF method is found to be insensitive to variations in μ'(s), thus requiring a complementary method such as using a point source for determination of μ'(s). The error for determining μ(a) decreases in very heterogeneous turbid media because of the local absorption extremes. The data acquisition time for obtaining the one-dimensional optical properties distribution is less than 8 s. This method can result in dramatically improved accuracy of light fluence rate calculation for CDFs for prostate PDT in vivo when the same model and geometry is used for forward calculations using the extrapolated tissue optical properties.

A review of in-vivo optical properties of human tissues and its impact on PDT

A thorough understanding of optical properties of biological tissues is critical to effective treatment planning for therapies such as photodynamic therapy (PDT). In the last two decades, new technologies, such as broadband diffuse spectroscopy, have been developed to obtain in vivo data in humans that was not possible before. We found that the in vivo optical properties generally vary in the ranges μ(a) = 0.03-1.6 cm⁻¹ and μ'(s) = 1.2-40 cm⁻¹, although the actual range is tissue-type dependent. We have also examined the overall trend of the absorption spectra (for μ(a) and μ'(s)) as a function of wavelength within a 95% confidence interval for various tissues in vivo. The impact of optical properties on light fluence rate is also discussed for various light application geometries including superficial, interstitial, and within a cavity.

Light penetration in the human prostate: a whole prostate clinical study at 763 nm

Photodynamic therapy (PDT) is being investigated as a treatment for localized prostate cancer. Photodynamic therapy uses a photosensitizing drug which is activated by a specific wavelength of light, in the presence of oxygen. The activated drug reacts with tissue oxygen to produce reactive oxygen species which are responsible for localized tissue necrosis. One of the determinants of the PDT effect is the penetration of light in the prostate. This study assesses the penetration depth of 763 nm light throughout the prostate. Eight men undergoing multiple hollow needle insertion for high dose rate brachytherapy were recruited. 763 nm light, produced by a diode laser, was delivered to the prostate using cylindrically diffusing optical fibers within the plastic needles. Light was detected at different distances from the source, using an isotropic detector within nearby needles. Penetration depth was calculated using the Boltzmann approximation to the diffusion equation. Delivery detector fiber separation was measured on computed tomography. The mean penetration depth was 0.57 cm, but there was within patient variation of a mean factor of 4.3. Further work is ongoing to assess the effect of such variability in light penetration, on the PDT effect.

Application of a biodegradable macromolecular contrast agent in dynamic contrast-enhanced MRI for assessing the efficacy of indocyanine green-enhanced photothermal cancer therapy

PURPOSE

To investigate the effectiveness of a polydisulfide-based biodegradable macromolecular contrast agent, (Gd-DTPA)-cystamine copolymers (GDCC), in assessing the efficacy of indocyanine green-enhanced photothermal cancer therapy using dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI).

MATERIALS AND METHODS

Breast cancer xenografts in mice were injected with indocyanine green and irradiated with a laser. The efficacy was assessed using DCE-MRI with GDCC of 40 kDa (GDCC-40) at 4 hours and 7 days after the treatment. The uptake of GDCC-40 by the tumors was fit to a two-compartment model to obtain tumor vascular parameters, including fractional plasma volume (f(PV)), endothelium transfer coefficient (K(PS)), and permeability surface area product (PS).

RESULTS

GDCC-40 resulted in similar tumor vascular parameters at three doses, with larger standard deviations at lower doses. The values of f(PV), K(PS), and PS of the treated tumors were smaller (P < 0.05) than those of untreated tumors at 4 hours after the treatment and recovered to pretreatment values (P > 0.05) at 7 days after the treatment.

CONCLUSION

DCE-MRI with GDCC-40 is effective for assessing tumor early response to dye-enhanced photothermal therapy and detecting tumor relapse after the treatment. GDCC-40 has a potential to noninvasively monitor anticancer therapies with DCE-MRI.

The role of photodynamic therapy (PDT) physics

Photodynamic therapy (PDT) is an emerging treatment modality that employs the photochemical interaction of three components: light, photosensitizer, and oxygen. Tremendous progress has been made in the last 2 decades in new technical development of all components as well as understanding of the biophysical mechanism of PDT. The authors will review the current state of art in PDT research, with an emphasis in PDT physics. They foresee a merge of current separate areas of research in light production and delivery, PDT dosimetry, multimodality imaging, new photosensitizer development, and PDT biology into interdisciplinary combination of two to three areas. Ultimately, they strongly believe that all these categories of research will be linked to develop an integrated model for real-time dosimetry and treatment planning based on biological response.

Motexafin lutetium-photodynamic therapy of prostate cancer: short- and long-term effects on prostate-specific antigen

PURPOSE

The time course of serum prostate-specific antigen (PSA) response to photodynamic therapy (PDT) of prostate cancer was measured.

EXPERIMENTAL DESIGN

Seventeen patients were treated in a phase I trial of motexafin lutetium-PDT. PDT dose was calculated in each patient as the product of the ex vivo measured pre-PDT photosensitizer level and the in situ measured light dose. Serum PSA level was measured within 2 months before PDT (baseline), and at day 1; weeks 1 to 3; months 1, 2, and 3; months 4 to 6; and months 7 to 11 after PDT.

RESULTS

At 24 hours after PDT, serum PSA increased by 98% +/- 36% (mean +/- SE) relative to baseline levels (P = 0.007). When patients were dichotomized based on median PDT dose, those who received high PDT dose showed a 119% +/- 52% increase in PSA compared with a 54% +/- 27% increase in patients treated at low PDT dose. Patients treated with high versus low PDT dose showed a median biochemical delay of 82 versus 43 days (P = 0.024), with biochemical delay defined as the length of time between PDT and a nonreversible increase in PSA to a value greater than or equal to baseline.

CONCLUSIONS

Results show PDT to induce large, transient increases in serum PSA levels. Patients who experienced high PDT dose showed greater short-term increase in PSA and a significantly more durable PSA response (biochemical delay). These data strongly promote the need for individualized delivery of PDT dose and assessment of treatment effect in PDT of prostate cancer. Information gained from such patient-specific measurements could facilitate the introduction of multiple PDT sessions in patients who would benefit.

Towards accurate in vivo spectroscopy of the human prostate

The recent interest in photodynamic therapy of human prostate cancer is accompanied by a need for techniques for in vivo monitoring of optical and physiological characteristics. We propose time-of-flight (TOF) spectroscopy in combination with Monte Carlo evaluation as a reliable optical technique for quantitative assessment of absorption, scattering, hemoglobin content and tissue oxygenation in the human prostate. For the first time, we demonstrate Monte Carlo-based evaluation of in vivo TOF photon migration data. We show that this approach is crucial in order to avoid the large errors associated with the use of time-resolved diffusion theory of light propagation in prostate-like tissues. This progress also allows us to present the first in vivo scattering spectroscopy of human prostate tissue. Furthermore, TOF spectroscopy, in contrast to the more common steady-state approach, is insensitive to bleedings, and has been found highly reliable (100% success rate).

Preliminary results of interstitial motexafin lutetium-mediated PDT for prostate cancer

BACKGROUND AND OBJECTIVES

Interstitial photodynamic therapy (PDT) is an emerging modality for the treatment of solid organ disease. Our group at the University of Pennsylvania has performed extensive studies that demonstrate the feasibility of interstitial PDT for prostate cancer. Our preclinical and clinical experience is herein detailed.

STUDY DESIGN/MATERIALS AND METHODS

We have treated 16 canines in preclinical studies, and 16 human subjects in a Phase I study, using motexafin lutetium-mediated PDT for recurrent prostate adenocarcinoma. Dosimetry of light fluence, drug level and oxygen distribution for these patients were performed.

RESULTS

We demonstrate the safe and comprehensive treatment of the prostate using PDT. However, there is significant variability in the dose distribution and the subsequent tissue necrosis throughout the prostate.

CONCLUSIONS

PDT is an attractive option for the treatment of prostate adenocarcinoma. However, the observed variation in PDT dose distribution translates into uncertain therapeutic reproducibility. Our future focus will be on the development of an integrated system that is able to both detect and compensate for dose variations in real-time, in order to deliver a consistent overall PDT dose distribution.

In vivo optical characterization of human prostate tissue using near-infrared time-resolved spectroscopy

The development of photodynamic therapy into a modality for treatment of prostate cancer calls for reliable optical dosimetry. We employ, for the first time, interstitial time-resolved spectroscopy to determine in vivo optical properties of human prostate tissue. Nine patients are included in the study, and measurements are conducted prior to primary brachytherapy treatment of prostate cancer. Intrasubject variability is examined by measuring across three tissue volumes within each prostate. The time-resolved instrumentation proves its usefulness by producing good signal levels in all measurements. We are able to present consistent values on reduced scattering coefficients (mu(s)'), absorption coefficients (mu(a)), and effective attenuation (mu(eff)) at the wavelengths 660, 786, and 916 nm. At 660 nm, mu(s)' is found to be 9+/-2 cm(-1), and mu(a) is 0.5+/-0.1 cm(-1). Derived values of mu(eff) are in the range of 3 to 4 cm(-1) at 660 nm, a result in good agreement with previously published steady state data. Total hemoglobin concentration (THC) and oxygen saturation are spectroscopically determined using derived absorption coefficients. Derived THC values are fairly variable (215+/-65 microM), while derived values of oxygen saturation are gathered around 75% (76+/-4%). Intrasubject variations in derived parameters correlate (qualitatively) with the heterogeneity exhibited in acquired ultrasound images.

Diverse optical characteristic of the prostate and light delivery system: implications for computer modelling of prostatic photodynamic therapy

OBJECTIVE

To explore the use of photodynamic therapy (PDT) as a minimally invasive form of treatment for organ-confined prostate cancer, for although there are several therapies, ablative treatments are associated with significant morbidity.

MATERIALS AND METHODS

Using the photosensitizer tin etiopurpurin, dogs were treated with interstitially placed laser fibres in an effort to validate PDT for treating prostate cancer. Earlier models assumed a uniform distribution of light output from a cylindrical fibre and a uniform attenuation coefficient throughout the prostate. Subsequent observations show that this model was too simple and that light radiance is not linear. To overcome under-treatment, a computer program to complement real-time fibre placement was developed.

RESULTS

As light radiance from interstitially placed laser fibres varies significantly from the commonly assumed ideal cylindrical emission, a predictive mathematical model of prostate PDT needs to consider the real emission. Also, the optical properties of the prostate, e.g. absorption and scattering of light, are anisotropic. Differences in the attenuation coefficient (combining absorption and scattering of light) also varied among different animals. Incorporating all these variables into a computer program produced a virtual model of the photo-ablated zone within +/- 2 mm of that observed in animals.

CONCLUSION

PDT of the prostate is not trivial and should benefit from computer-aided methods as it is developed for clinical use.

Optical properties of human prostate at 732 nm measured in mediated photodynamic therapy

Characterization of the tissue light penetration in prostate photodynamic therapy (PDT) is important to plan the arrangement and weighting of light sources so that sufficient light fluence is delivered to the treatment volume. The optical properties (absorption [mu(a)], transport scattering [mu(s)'] and effective attenuation [mu(eff)] coefficients) of 13 patients with locally recurrent prostate cancer were measured in situ using interstitial isotropic detectors. Measurements were made at 732 nm before and after motexafin lutetium (MLu)-mediated PDT in four quadrants. Optical properties were derived by applying the diffusion theory to the fluence rates measured at several distances (0.5-5 cm) from a point source. mu(a) and mu(s)' varied between 0.07 and 1.62 cm(-1) (mean 0.37 +/- 0.24 cm(-1)) and 1.1 and 44 cm(-1) (mean 14 +/- 11 cm(-1)), respectively. mu(a) was proportional to the concentration of MLu measured by an ex vivo fluorescence assay. We have observed, on average, a reduction of the MLu concentration after PDT, presumably due to the PDT consumption of MLu. mu(eff) varied between 0.91 and 6.7 cm(-1) (mean 2.9 +/- 0.7 cm(-1)), corresponding to an optical penetration depth (delta = 1/micro(eff)) of 0.1-1.1 cm (mean 0.4 +/- 0.1 cm). The mean penetration depth at 732 nm in human prostate is at least two times smaller than that found in normal canine prostates, which can be explained by a four times increase of the mean value of mu(s)' in human prostates. The mean light fluence rate per unit source strength at 0.5 cm from a point source was 1.5 +/- 1.1 cm(-2), excluding situations when bleeding occurs. The total number of measurements was N = 121 for all mean quantities listed above. This study showed significant inter- and intraprostatic differences in the optical properties, suggesting that a real-time dosimetry measurement and feedback system for monitoring light fluences during treatment should be considered for future PDT studies.

Determination of the distribution of light, optical properties, drug concentration, and tissue oxygenation in-vivo in human prostate during motexafin lutetium-mediated photodynamic therapy

It is desirable to quantify the distribution of the light fluence rate, the optical properties, the drug concentration, and the tissue oxygenation for photodynamic therapy (PDT) of prostate cancer. We have developed an integrated system to determine these quantities before and after PDT treatment using motorized probes. The optical properties (absorption (micro(a)), transport scattering (micro(s'), and effective attenuation (micro(eff)) coefficients) of cancerous human prostate were measured in-vivo using interstitial isotropic detectors. Measurements were made at 732 nm before and after motexafin lutetium (MLu) mediated PDT at different locations along each catheter. The light fluence rate distribution was also measured along the catheters during PDT. Diffuse absorption spectroscopy measurement using a white light source allows extrapolation of the distribution of oxygen saturation StO2, total blood volume ([Hb]t), and MLu concentration. The distribution of drug concentration was also studied using fluorescence from a single optical fiber, and was found to be in good agreement with the values determined by absorption spectroscopy. This study shows significant inter- and intra-prostatic variations in the tissue optical properties and MLu drug distribution, suggesting that a real-time dosimetry measurement and feedback system for monitoring these values during treatment should be considered in future PDT studies.

Effect of Tumor Host Microenvironment on Photodynamic Therapy in a Rat Prostate Tumor Model

Purpose: Tumor host microenvironment plays an important role in tumor growth, metastasis, and response to cancer therapy. In this study, the influence of tumor host environment on tumor pathophysiology, photosensitizer distribution, and photodynamic therapy (PDT) treatment effect was examined in the metastatic at lymph node and lung (MatLyLu) rat prostate tumor.

Experimental Design: MatLyLu tumors implanted in different host environment [i.e., orthotopically (in the prostate) or s.c.] were compared for difference in vessel density, average vessel size, vascular permeability, tumor vascular endothelial growth factor production, and tumor oxygenation. Uptake of photosensitizer verteporfin in tumors in both sites was determined by fluorescence microscopy. To compare tumor response to PDT, both orthotopic and s.c. MatLyLu tumors were given the same doses of verteporfin and laser light treatment, and PDT-induced tumor necrotic area was measured histologically.

Results: Orthotopic MatLyLu tumors were found to grow faster, have higher vessel density and more permeable vasculature, have higher vascular endothelial growth factor protein levels, and have lower tumor hypoxic fraction than the s.c. tumors. Uptake of photosensitizer verteporfin in the orthotopic tumor was higher than in the s.c. tumors at 15 minutes after injection (1 mg/kg, i.v.), and became similar at 3 hours after injection. For the vascular targeting PDT treatment (0.25 mg/kg verteporfin, 50 J/cm2 at 50 mW/cm2, 15 minutes drug-light interval), there was no significant difference in PDT-induced tumor necrotic area between the orthotopic and s.c. tumors, with 85% to 90% necrosis in both types of tumors. However, tumor necrosis induced by the cellular targeting PDT (1 mg/kg verteporfin, 50 J/cm2 at 50 mW/cm2, 3 hours drug-light interval) was significantly different in the orthotopic (64%) versus the s.c. (29%) tumors.

Conclusions: Tumor host environment can significantly affect photosensitizer verteporfin distribution and PDT treatment effect. Verteporfin-PDT regimen targeting tumor cells is more sensitive to such influence than the vascular targeting PDT. Our study showed the importance of tumor host environment in determining tumor physiologic properties and tumor response to PDT. To obtain clinically relevant information, orthotopic tumor model should be used in the experimental studies.

OPTICAL CHARACTERISTICS OF THE CANINE PROSTATE AT 665 NM SENSITIZED WITH TIN ETIOPURPURIN DICHLORIDE: NEED FOR REAL-TIME MONITORING OF PHOTODYNAMIC THERAPY

PURPOSE

Photodynamic therapy (PDT) is an emerging, minimally invasive therapy for prostate cancer that depends on the sequestration of a photosensitizing drug within targeted tissue. The photosensitizer is subsequently activated by light of a specific wavelength, resulting in destruction of the targeted tissue. Successful treatment requires knowledge of the optical properties of the target tissue, a critical element for therapy.

MATERIALS AND METHODS

Adult canines were injected with tin etiopurpurin dichloride (1.0 mg/kg) as a liposome emulsion vehicle in saline 24 hours prior to light treatment. Laser light was delivered to the prostate via a 400 microm optical fiber fitted with a 2.0 cm cylindrical diffuser and optical properties of the prostate were measured.

RESULTS

In this study we determined the attenuation coefficient and critical fluence in the canine prostate. Our studies shown that the attenuation coefficient is not uniform but higher at the base (average for all animals 2.59 to 2.79 cm-1) than in the mid section or apex of the prostate (1.71 to 1.90 cm-1). Significant differences among dogs (0.11 to 12.70 cm-1) were found. In some cases we observed a fluctuation of the attenuation coefficient during treatment. We also established experimentally the minimum energy (1449 mJ/cm2) needed (critical fluence) to produce necrosis. Experimentally establishing the values of effective attenuation and critical fluence is necessary to predict the area of ablation during PDT and protect surrounding organs from over treatment.

CONCLUSIONS

Based on our results it is evident that for PDT of the prostate to be successful the optical parameters of the prostate must be measured and monitored during treatment. We suggest that the optimum way of doing this is real-time computerized monitoring combined with simulation PDT.

Photodynamic therapy: a new approach to prostate cancer

Photodynamic therapy (PDT) is based on the concept that light irradiation can change an inert substance into an active one. In urology, hematoporphyrin derivative (HpD) and Photofrin (Axcan Scandipharm Inc., Birmingham, AL) are used most commonly as photosensitizing agents predominantly for the treatment of transitional cell carcinoma of the bladder. To investigate the basics for PDT of prostate cancer, several studies were performed on the optical characteristics of prostate tissue and prostate carcinoma tissue in vitro and in vivo and on the penetration depths of different laser wavelengths. Initial experimental studies to treat prostate cancer with PDT using HpD were done on Dunning tumors in rats. Combined with interstitial applicators, photodynamic therapy seems to have a great potential in the treatment of prostate carcinoma. However, it is an experimental treatment and even a preliminary evaluation will be possible only after the conclusion of clinical studies with the corresponding long-term results.

Photodynamic therapy with Pd-Bacteriopheophorbide (TOOKAD): successful in vivo treatment of human prostatic small cell carcinoma xenografts

Small cell carcinoma of the prostate (SCCP), although relatively rare, is the most aggressive variant of prostate cancer, currently with no successful treatment. It was therefore tempting to evaluate the response of this violent malignancy and its bone lesions to Pd-Bacteriopheophorbide (TOOKAD)-based photodynamic therapy (PDT), already proven by us to efficiently eradicate other aggressive non-epithelial solid tumors. TOOKAD is a novel bacteriochlorophyll-derived, second-generation photosensitizer recently, developed by us for the treatment of bulky tumors. This photosensitizer is endowed with strong light absorbance (epsilon(0) approximately 10(5) mol(-1) cm(-1)) in the near infrared region (lambda=763nm), allowing deep tissue penetration. The TOOKAD-PDT protocol targets the tumor vasculature leading to inflammation, hypoxia, necrosis and tumor eradication. The sensitizer clears rapidly from the circulation within a few hours and does not accumulate in tissues, which is compatible with the treatment of localized tumor and isolated metastases. Briefly, male CD1-nude mice were grafted with the human SCCP (WISH-PC2) in 3 relevant anatomic locations: subcutaneous (representing tumor mass), intraosseous (representing bone metastases) and orthotopically within the murine prostate microenvironment. The PDT protocol consisted of i.v. administration of TOOKAD (4 mg/kg), followed by immediate illumination (650-800 nm) from a xenon light source or a diode laser emitting at 770 nm. Controls included untreated animals or animals treated with light or TOOKAD alone. Tumor volume, human plasma chromogranin A levels, animal well being and survival were used as end points. In addition, histopathology and immunohistochemistry were used to define the tumor response. Subcutaneous tumors exhibited complete healing within 28-40 days, reaching an overall long-term cure rate of 69%, followed for 90 days after PDT. Intratibial WISH-PC2 lesions responded with complete tumor elimination in 50% of the treated mice at 70-90 days after PDT as documented histologically. The response of the orthotopic model was also analyzed histologically with similar results. The study with this model suggests that TOOKAD-based PDT can reach large tumors and is a feasible, efficient and well-tolerated approach for minimally invasive treatment of local and disseminated SCCP.

In vivo optical properties of normal canine prostate at 732 nm using motexafin lutetium-mediated photodynamic therapy

The optical properties (absorption [mu(a)], transport scattering [mu('s)] and effective attenuation [mu(eff)] coefficients) of normal canine prostate were measured in vivo using interstitial isotropic detectors. Measurements were made at 732 nm before, during and after motexafin lutetium (MLu)-mediated photodynamic therapy (PDT). They were derived by applying the diffusion theory to the in vivo peak fluence rates measured at several distances (3, 6, 9, 12 and 15 mm) from the central axis of a 2.5 cm cylindrical diffusing fiber (CDF). Mu(a) and mu('s) varied between 0.03-0.58 and 1.0-20 cm(-1), respectively. Mu(a) was proportional to the concentration of MLu.Mu(eff) varied between 0.33 and 4.9 cm(-1) (mean 1.3 +/- 1.1 cm(-1)), corresponding to an optical penetration depth (8 = 1/(mu(eff)) of 0.5-3 cm (mean 1.3 +/- 0.8 cm). The mean light fluence rate at 0.5 cm from the CDF was 126 +/- 48 mW/cm2 (N = 22) when the total power from the fiber was 375 mW (150 mW/cm). This study showed significant inter- and intraprostatic differences in the optical properties, suggesting that a real-time dosimetry measurement and feedback system for monitoring light fluences during treatment should be advocated for future PDT studies. However, no significant changes were observed before, during and after PDT within a single treatment site.

Preclinical studies in normal canine prostate of a novel palladium-bacteriopheophorbide (WST09) photosensitizer for photodynamic therapy of prostate cancers

Photodynamic therapy (PDT) uses light to activate a photosensitizer to achieve localized tumor control. In this study, PDT mediated by a second-generation photosensitizer, palladium-bacteriopheophorbide WST09 (Tookad) was investigated as an alternative therapy for prostate cancer. Normal canine prostate was used as the animal model. PDT was performed by irradiating the surgically exposed prostate superficially or interstitially at 763 nm to different total fluences (100 or 200 J/cm2; 50, 100 or 200 J/cm) at 5 or 15 min after intravenous administration of the drug (2 mg/kg). Areas on the bladder and colon were also irradiated. The local light fluence rate and temperature were monitored by interstitial probes in the prostate. All animals recovered well, without urethral complications. During the 1 week to 3 month post-treatment period, the prostates were harvested for histopathological examination. The PDT-induced lesions showed uniform hemorrhagic necrosis and atrophy, were well delineated from the adjacent normal tissue and increased linearly in diameter with the logarithm of the delivered light fluence. A maximum PDT-induced lesion size of over 3 cm diameter could be achieved with a single interstitial treatment. There was no damage to the bladder or rectum caused by scattered light from the prostate. The bladder and rectum were also directly irradiated with PDT. At 80 J/cm2, a full-depth necrosis was observed but resulted in no perforation. At 40 J/cm2, PDT produced minimal damage to the bladder or rectum. On the basis of optical dosimetry, we have estimated that 20 J/cm2 is the fluence required to produce prostatic necrosis. Thus, the normal structure adjacent to the prostate can be safely preserved with careful dosimetry. At therapeutic PDT levels, there was no structural or functional urethral damage even when the urethra was within the treated region. Hence, Tookad-PDT appears to be a promising candidate for prostate ablation in patients with recurrent, or possibly even primary, prostate cancer.

New technology for deep light distribution in tissue for phototherapy

Photodynamic therapy is one of several techniques developed for phototherapy for solid cancers and hematologic malignancies. Photodynamic therapy is a treatment that utilizes a molecular energy exchange between visible light and a photosensitive drug, which results in the production of 1O2, a highly reactive cytocidal oxygen species. The effect is limited to the region where light and drug are combined so that malignant tissue is destroyed and the usual side effects associated with standard cancer therapies are avoided. The light component of photodynamic therapy is customarily generated via dye-pumped or diode lasers. The cost and the complexity of lasers have seriously limited the clinical use of photodynamic therapy for malignancies. A new device technology, based on light-emitting diodes, has been developed (Light Sciences Corporation, Issaquah, WA) that allows light production inside the target tissue. This new technology will expand the current range of indications that are treatable with photodynamic therapy to include moderate- and large-volume refractorytumors. Conventional photodynamic therapy utilizes the delivery of intense light for seconds or minutes. The new approach differs from conventional photodynamic therapy in that it combines a novel interstitial light delivery system with prolonged photoactivation of photosensitive drugs. Prolonging photoactivation time in order to deliver a higher light dose results in an amplification effect, whereby the repeated activation of each photosensitive drug molecule leads to the generation of many thousands of 1O2 molecules. The production of overwhelming numbers of these powerful oxidants in individual cells and the vascular supply of tumors leads to irreversible damage and death of the targeted lesions. Results of preclinical studies have indicated a significant correlation between increased duration of photoactivation and increased volume and depth of photodynamic therapy-induced necrosis. The new developments will enable photodynamic therapy to be used effectively against refractory bulky disease as frontline therapy or in combination with chemotherapy, radiation therapy, or biologics. Perhaps most promising, many patients with advanced refractory disease may now be relieved of symptoms or may return to the treatable population.

Synthesis, spectra and photophysics of some free base tetrafluoroalkyl and tetrafluoroaryl porphyrins with potential applications in imaging

The synthesis, characterization and photophysical properties of two perfluoroalkyl (5,10,15,20-tetrakis-[trifluoromethyl]- and [heptafluoropropyl]-porphyrin) and two perfluoroaryl (5,10,15,20-tetrakis-[2,6-difluorophenyl]- and [pentafluorophenyl]-porphyrin) are described, with reference to their potential in both photodynamic therapy (PDT) and in vivo imaging by fluorescence and 19F nuclear magnetic resonance spectroscopy. Absorption and fluorescence spectra, fluorescence lifetimes and triplet-singlet difference spectra are reported. Triplet yields have been obtained by flash photolysis and pulse radiolysis, whereas yields of sensitized singlet oxygen formation have been determined by time-resolved phosphorimetry. All four compounds show high yields of triplet formation and singlet oxygen sensitization. The spectral properties, stability and attractive solubility characteristics of the perfluoroalkyl derivatives make them particularly suitable candidates for future study for applications in PDT.

Laser dosimetry studies in the prostate

OBJECTIVE

To review the currently available data of photodynamic therapy (PDT) optical dosimetry for possible prostatic applications.

SUMMARY BACKGROUND DATA

PDT is a new cancer treatment modality often used as an alternative tumor treatment method. Recently, PDT has been suggested as an alternative therapy for prostatic carcinoma and BPH.

METHODS

PDT: utilizes light and a preadministered photosensitizer drug to achieve localized tumor control. This article reviews currently available data on optical dosimetry of PDT in both human and canine prostates.

RESULTS

At 630 nm, a common wavelength used for Photofrin PDT, results indicate that light penetration is similar in cancerous and normal prostatic tissue. Because of limited light penetration, multiple fiber irradiation is necessary if eradicating the entire prostate glad is the ultimate goal. The available data also show that dynamic changes occur in light fluence rate distribution during PDT irradiation.

CONCLUSIONS

PDT can be used to destroy prostatic tissue. Real-time optical dosimetry is necessary if accurate lesion volume control is desired.

The biology of photodynamic therapy

The subcellular, cellular and tissue/tumour interactions with non-toxic photosensitizing chemicals plus non-thermal visible light (photodynamic therapy (PDT) are reviewed. The extent to which endothelium/vasculature is the primary target is discussed, and the biochemical opportunities for manipulating outcome highlighted. The nature of tumour destruction by PDT lends itself to imaging outcome by MRI and PET.