Photodynamic Therapy for Prostate Cancer Recurrence After Radiotherapy: A Phase I Study:

Versatile Design of Organic Polymeric Nanoparticles for Photodynamic Therapy of Prostate Cancer

Radical prostatectomy is a primary treatment option for localized prostate cancer (PCa), although high rates of recurrence are commonly observed postsurgery. Photodynamic therapy (PDT) has demonstrated efficacy in treating nonmetastatic localized PCa with a low incidence of adverse events. However, its limited efficacy remains a concern. To address these issues, various organic polymeric nanoparticles (OPNPs) loaded with photosensitizers (PSs) that target prostate cancer have been developed. However, further optimization of the OPNP design is necessary to maximize the effectiveness of PDT and improve its clinical applicability. This Review provides an overview of the design, preparation, methodology, and oncological aspects of OPNP-based PDT for the treatment of PCa.

Perspectives on interstitial photodynamic therapy for malignant tumors

SIGNIFICANCE

Despite remarkable advances in the core modalities used in combating cancer, malignant diseases remain the second largest cause of death globally. Interstitial photodynamic therapy (IPDT) has emerged as an alternative approach for the treatment of solid tumors.

AIM

The aim of our study is to outline the advancements in IPDT in recent years and provide our vision for the inclusion of IPDT in standard-of-care (SoC) treatment guidelines of specific malignant diseases.

APPROACH

First, the SoC treatment for solid tumors is described, and the attractive properties of IPDT are presented. Second, the application of IPDT for selected types of tumors is discussed. Finally, future opportunities are considered.

RESULTS

Strong research efforts in academic, clinical, and industrial settings have led to significant improvements in the current implementation of IPDT, and these studies have demonstrated the unique advantages of this modality for the treatment of solid tumors. It is envisioned that further randomized prospective clinical trials and treatment optimization will enable a wide acceptance of IPDT in the clinical community and inclusion in SoC guidelines for well-defined clinical indications.

CONCLUSIONS

The minimally invasive nature of this treatment modality combined with the relatively mild side effects makes IPDT a compelling alternative option for treatment in a number of clinical applications. The adaptability of this technique provides many opportunities to both optimize and personalize the treatment.

Photodynamic therapy for prostate cancer - A narrative review

This article is a review of approaches to treatment of low and high-grade prostate cancer including a discussion of active treatment vs. active surveillance for patients with low-grade prostate cancer. In particular, we will review PDT as an option for active treatment of low-grade prostate cancer considered in light of recent clinical trials. The mechanism and clinical methods of PDT application and the key points from clinical trials using PDT for prostate cancer with the photosensitizers m-tetrahydroxyphenyl chloride, protoporphyrin IX, motexafin lutetium, padoporfin, and padeliporfin between the years 2002 and 2017 are reviewed. Recently developed methodologies for photodynamic prostate cancer treatment that are in the experimental stage, photodynamic diagnosis, fluorescence guided resection, and PSMA-targeted PDT will also be discussed.

Photodynamic therapy in spinal metastases: a qualitative analysis of published results

The current study was to perform qualitative comparison of photodynamic therapy (PDT), based on previously published articles on spinal disease distribution status before and after treatment. Spinal metastasis, the migration of primary cancer cells and establishment of secondary tumors in the spine. We electronically searched CENTRAL (The Cochrane Library 2012), MEDLINE, EMBASE, CINAHL and AMED (from their beginning to December 31, 2012) to identify published studies assessing the effectiveness of PDT in spinal metastases. Our inclusion criteria resulted in only 4 articles, all in mice models. Due to study limitations and sparse data, the quality of evidence for all outcomes was low. Our analyses shows that effects on stereological and mechanical properties observed at the 1-week time point post-PDT are maintained at a longer 6-week time point, with combined PDT + bisphosphonate treatment being the most beneficial in terms of bone enhancement. Additionally, the combination of PDT + radiation therapy also demonstrated significant increases in stereological parameters, suggesting that previous radiation therapy treatment does not preclude the bone-enhancing effects of PDT and in fact may be synergistic in the longer term. The bone-enhancing effects of PDT in combination with conventional treatments, and its ability to destroy metastatic human breast cancer cells within bone, present PDT as an attractive novel treatment for spinal metastasis. The positive results from these preclinical studies might motivate future clinical translation of PDT for spinal metastasis.

Enhanced prostate cancer targeting by modified protease sensitive photosensitizer prodrugs

Prodrugs combining macromolecular delivery systems with site-selective drug release represent a powerful strategy to increase selectivity of anticancer agents. We have adapted this strategy to develop new polymeric photosensitizer prodrugs (PPP) sensitive to urokinase-like plasminogen activator (uPA). In these compounds (to be referred to as uPA-PPPs) multiple copies of pheophorbide a are attached to a polymeric carrier via peptide linkers that can be cleaved by uPA, a protease overexpressed in prostate cancer (PCa). uPA-PPPs are non-phototoxic in their native state but become fluorescent and produce singlet oxygen after uPA-mediated activation. In the present work, we studied the influence of side-chain modifications, molecular weight, and overall charge on the photoactivity and pharmacokinetics of uPA-PPPs. An in vitro promising candidate with convertible phototoxicity was then further investigated in vivo. Systemic administration resulted in a selective accumulation and activation of the prodrug in luciferase transfected PC-3 xenografts, resulting in a 4-fold increase in fluorescence emission over time. Irradiation of fluorescent tumors induced immediate tumor cell eradication as shown by whole animal bioluminescence imaging. PDT with uPA-PPP could therefore provide a more selective treatment of localized PCa and reduce side effects associated with current radical treatments.

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.

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.

A mechanism-based combination therapy reduces local tumor growth and metastasis in an orthotopic model of prostate cancer

Therapy-induced stimulation of angiogenic molecules can promote tumor angiogenesis leading to enhanced tumor growth and cancer metastasis. Several standard and emerging therapies, such as radiation and photodynamic therapy (PDT), can induce angiogenic molecules, thus limiting their effectiveness. PDT is approved for the treatment of several cancers; however, its induction of vascular endothelial growth factor (VEGF) creates conditions favorable to enhanced tumor growth and metastasis, therefore mitigating its cytotoxic and antivascular effects. This is the first report showing that subcurative PDT in an orthotopic model of prostate cancer (LNCaP) increases not only VEGF secretion (2.1-fold) but also the fraction of animals with lymph node metastases. PDT followed by administration of an antiangiogenic agent, TNP-470, abolished this increase and reduced local tumor growth. On the other hand, administration of TNP-470 before PDT was less effective at local tumor control. In addition, animals in all groups, except in the PDT + TNP-470 group, had a weight loss of >3 g at the time of sacrifice; the weight of the animals in the PDT + TNP-470 group did not change. The significant reduction (P < 0.05) in tumor weight and volume observed between the PDT + TNP-470 group and the control group suggests that the combination of PDT and antiangiogenic treatment administered in the appropriate sequence was not only more effective at controlling local tumor growth and metastases but also reduced disease-related toxicities. Such molecular response-based combinations merit further investigations as they enhance both monotherapies and lead to improved treatment outcomes.

Mechanistic Investigation and Implications of Photodynamic Therapy Induction of Vascular Endothelial Growth Factor in Prostate Cancer

Photodynamic therapy (PDT) is now an approved therapeutic modality, and induction of vascular endothelial growth factor (VEGF) following subcurative PDT is of concern as VEGF may provide a survival stimulus to tumors. The processes that limit the efficacy of PDT warrant investigation so that mechanism-based interventions may be developed. This study investigates VEGF increase following subcurative PDT using the photosensitizer benzoporphyrin derivative (BPD) both in an in vitro and in an orthotopic model of prostate cancer using the human prostate cancer cell line LNCaP. The two subcurative doses used, 0.25 and 0.5 J/cm(2), mimicked subcurative PDT and elicited a 1.6- and 2.1-fold increase, respectively, in secreted VEGF 24 hours following PDT. Intracellular VEGF protein measurement and VEGF mRNA showed a 1.4- and 1.6-fold increase only at 0.5 J/cm(2). In vivo subcurative PDT showed an increase in VEGF by both immunohistochemistry and ELISA. In vitro analysis showed no activation of hypoxia-inducible factor-1alpha (HIF-1alpha) or cyclooxygenase-2 (COX-2) following subcurative PDT; furthermore, small interfering RNA inhibition of HIF-1alpha and COX-2 inhibitor treatment had no effect on PDT induction of VEGF. PDT in the presence of phosphatidylinositol 3-kinase/AKT inhibitor or mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase inhibitor still induced VEGF. However, subcurative PDT increased phosphorylated p38 and stress-activated protein kinase/c-Jun NH(2)-terminal kinase. The p38 MAPK inhibitor abolished PDT induction of VEGF. The results establish the importance of VEGF in subcurative BPD-PDT of prostate cancer and suggest possible molecular pathways for its induction. These findings should provide the basis for the development of molecular-based interventions for enhancing PDT and merit further studies.

Effects of photodynamic therapy on peripheral nerve: in situ compound-action potentials study in a canine model

OBJECTIVE

Our aim is to investigate the effects of photodynamic therapy (PDT) on peripheral nerve conductivity.

BACKGROUND DATA

Interstitial PDT has been demonstrated as a promising treatment modality for prostate cancer. However, the sensitivity of nerves, in the immediate vicinity of the prostate gland, to PDT procedures has not been studied. This study attempts to establish an in situ canine model to evaluate direct PDT effect on peripheral nerves.

METHODS

PDT was performed by irradiating the cutaneous branches of the saphenous nerve at 763 nm with light doses of 50-200 J/cm2 after i.v. infusion of the photosensitizer Tookad (0-2 mg/kg). Evoked compound-action potentials (CAP) were recorded directly from the surface of the saphenous nerve. The latencies to onset and conduction velocities were determined during PDT and 1-week post-PDT.

RESULTS

Nerve and surrounding tissue damage corresponded well with drug/light doses. With Tookad doses of 2 mg/kg, treatment with 50 J/cm2 induced little change in saphenous nerve conduction properties. However, treatment with 100 J/cm2 resulted in localized nerve injury and decreases in nerve conduction velocities, and treatment with 200 J/cm2 severely damaged the nerve.

CONCLUSIONS

This canine model adequately demonstrates effects of Tookad PDT on peripheral nerves. Direct irradiation of 100-200 J/cm2 can alter nerve conduction and induce nerve damage. Therefore, possible side effects of interstitial PDT on the pelvic plexus need to be investigated in future studies.

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.

Transperineal in vivo fluence-rate dosimetry in the canine prostate during SnET2-mediated PDT

Advances in photodynamic therapy (PDT) treatment for prostate cancer can be achieved either by improving selectivity of the photosensitizer towards prostate gland tissue or improving the dosimetry by means of individualized treatment planning using currently available photosensitizers. The latter approach requires the ability to measure, among other parameters, the fluence rate at different positions within the prostate and the ability to derive the tissue optical properties. Here fibre optic probes are presented capable of measuring the fluence rate throughout large tissue volumes and a method to derive the tissue optical properties for different volumes of the prostate. The responsivity of the sensors is sufficient to detect a fluence rate of 0.1 mW cm(-2). The effective attenuation coefficient in the canine prostate at 660 nm is higher at the capsule (2.15+/-0.19 cm(-1)) than in proximity of the urethra (1.84+/-0.36 cm(-1)). Significant spatial and temporal intra- and inter-canine variability in the tissue optical properties was noted, highlighting the need for individualized monitoring of the fluence rate for improved dosimetry.

Photodynamic therapy of prostate cancer by means of 5-aminolevulinic acid-induced protoporphyrin IX - in vivo experiments on the dunning rat tumor model

OBJECTIVE

In order to expand the use of photodynamic therapy (PDT) in the treatment of prostate carcinoma (PCA), the aim of this study was to evaluate PDT by means of 5-aminolevulinic acid (5-ALA)-induced protoporphyrin IX (PPIX) in an in vivo tumor model.

METHODS

The model used was the Dunning R3327 tumor. First of all, the pharmacokinetics and the localization of PPIX were obtained using fluorescence measurement techniques. Thereafter, PDT using 150 mg 5-ALA/kg b.w. i.v. was performed by homogenous irradiation of the photosensitized tumor (diode laser lambda = 633 nm). The tumors were resected 2 days post-PDT and the extent of the necrosis was determined histopathologically.

RESULTS

The kinetics of PPIX fluorescence revealed a maximum intensity in the tumor tissue within 3 and 4.5 h post-application of 5-ALA. At this time, specific PPIX fluorescence could be localized selectively in the tumor cells. The PDT-induced necrosis (n = 18) was determined to be 94 +/- 12% (range 60-100%), while the necrosis of the controls (n = 12) differs significantly (p < 0.01), being less than 10%.

CONCLUSION

These first in vivo results demonstrate the effective potential of 5-ALA-mediated PDT on PCA in an animal model.