Photodynamic therapy of pigmented choroidal melanomas using a liposomal preparation of benzoporphyrin derivative

Evaluation of eye melanoma treatments in rabbits: A systematic review

Melanomas are the most common cancer of the eye in canines, felines and humans. The treatment approaches vary, since no gold standard exists. Therefore, this systematic review aimed to compare the treatment modalities in ocular melanoma in rabbits. Medline/PubMed, Cochrane Library, Web of Science and Embase were searched for articles published until 21 April 2021 in English, Portuguese or Spanish, reporting animal studies evaluating photodynamic therapy (PDT), laser, radiotherapy or surgical excision. Twenty-seven articles were included for the qualitative synthesis, with publication dates from 1970 to 2018. Of the selected studies, 19 used PDT, six used radiotherapy and two used laser as treatment. No studies regarding surgical therapy that met the inclusion criteria were obtained. The tumour therapy results were evaluated in a heterogeneous manner for different periods and various methods, including microscopy, angiographic, histological examination, fundoscopy, ultrasound exam and electroretinogram. The treatment modalities analysed successfully treated the ocular melanoma, with tumour necrosis being commonly observed. Despite the therapeutic efficacy shown, side effects have been reported for all the therapies. The studies showed high heterogeneity, and therefore, in the future, new studies should be carried out to increase knowledge about ocular melanoma treatment. The analysed therapies can be used successfully in the treatment of ocular melanoma, with more conservative options such as PDT presenting great potential.

Long-term Outcomes of Small Pigmented Choroidal Melanoma Treated with Primary Photodynamic Therapy

PURPOSE

To report the long-term outcomes of patients with small, pigmented, posteriorly located choroidal melanoma undergoing primary treatment using photodynamic therapy (PDT) with verteporfin at the London Ocular Oncology Service.

DESIGN

Retrospective, interventional, consecutive case series.

PARTICIPANTS

All patients undergoing primary treatment using PDT with verteporfin from April 2014 to December 2015 and followed until December 2019.

METHODS

This is a long-term follow-up study of the same cohort of patients previously reported by our group in 2017 and 2018.

MAIN OUTCOME MEASURES

Local tumor control, visual outcomes, and metastasis-free survival.

RESULTS

Twenty-six patients were included with a mean (± standard deviation) age and tumor thickness of 62 ± 14 years and 1.3 ± 0.5 mm, respectively. Tumors were posteriorly located (mean distance to optic nerve and fovea = 2.0 ± 2.2 mm and 1.6 ± 1.5 mm, respectively), and the majority were fully pigmented (73%). Overall, patients were followed for a median (interquartile range [IQR], range) of 49.5 (15.3, 7.0-66.0) months from first PDT to last follow-up. Over the course of this study, 14 of 26 (54%) have developed a local recurrence at a median of 20.0 months (20.5, 4.7-60.9 months). The most common pattern of recurrence was an isolated increase in basal dimensions (9/14; 64%). Median (IQR) final logarithm of the minimum angle of resolution visual acuity of the whole cohort was 0.2 (0.5). The only statistically significant difference in baseline and outcome characteristics between treatment failures and nonfailures was the distance to the fovea (median [IQR], 0.5 [1.3] vs. 2.5 [2.8]; P = 0.002) and final logarithm of the minimum angle of resolution visual acuity (median [IQR], 0.50 [0.80] vs. 0.00 [0.14]; P = 0.002), respectively.

CONCLUSIONS

Although treatment of small pigmented posterior choroidal melanoma with PDT effectively preserves visual acuity, 5-year treatment-success calculated by Kaplan-Meier analysis was only 38.4%. Recurrences after PDT tend to occur along the tumor edges, often with minimal increase in thickness. Given the substantial risk of treatment failure, primary PDT with vertepofrin is recommended in exceptional cases of choroidal melanoma, for which other treatments with greater tumor control are not a feasible option.

Nanoparticle-Mediated Combination Therapy: Two-in-One Approach for Cancer

Cancer represents a group of heterogeneous diseases characterized by uncontrolledgrowth and spread of abnormal cells, ultimately leading to death. Nanomedicine plays a significantrole in the development of nanodrugs, nanodevices, drug delivery systems and nanocarriers. Someof the major issues in the treatment of cancer are multidrug resistance (MDR), narrow therapeuticwindow and undesired side effects of available anticancer drugs and the limitations of anticancerdrugs. Several nanosystems being utilized for detection, diagnosis and treatment such as theranosticcarriers, liposomes, carbon nanotubes, quantum dots, polymeric micelles, dendrimers and metallicnanoparticles. However, nonbiodegradable nanoparticles causes high tissue accumulation andleads to toxicity. MDR is considered a major impediment to cancer treatment due to metastatictumors that develop resistance to chemotherapy. MDR contributes to the failure of chemotherapiesin various cancers, including breast, ovarian, lung, gastrointestinal and hematological malignancies.Moreover, the therapeutic efficiency of anticancer drugs or nanoparticles (NPs) used alone is lessthan that of the combination of NPs and anticancer drugs. Combination therapy has long beenadopted as the standard first-line treatment of several malignancies to improve the clinical outcome.Combination therapy with anticancer drugs has been shown to generally induce synergistic drugactions and deter the onset of drug resistance. Therefore, this review is designed to report andanalyze the recent progress made to address combination therapy using NPs and anticancer drugs.We first provide a comprehensive overview of the angiogenesis and of the different types of NPscurrently used in treatments of cancer; those emphasized in this review are liposomes, polymericNPs, polymeric micelles (PMs), dendrimers, carbon NPs, nanodiamond (ND), fullerenes, carbonnanotubes (CNTs), graphene oxide (GO), GO nanocomposites and metallic NPs used forcombination therapy with various anticancer agents. Nanotechnology has provided the convenienttools for combination therapy. However, for clinical translation, we need continued improvementsin the field of nanotechnology.

Specific Targeting of Melanotic Cells with Peptide Ligated Photosensitizers for Photodynamic Therapy

A strategy combining covalent conjugation of photosensitizers to a peptide ligand directed to the melanocortin 1 (MC1) receptor with the application of sequential LED light dosage at near-IR wavelengths was developed to achieve specific cytotoxicity to melanocytes and melanoma (MEL) with minimal collateral damage to surrounding cells such as keratinocytes (KER). The specific killing of melanotic cells by targeted photodynamic therapy (PDT) described in this study holds promise as a potentially effective adjuvant therapeutic method to control benign skin hyperpigmentation or superficial melanotic malignancy such as Lentigo Maligna Melanoma (LMM).

Nanomedicine in the application of uveal melanoma

Rapid advances in nanomedicine have significantly changed many aspects of nanoparticle application to the eye including areas of diagnosis, imaging and more importantly drug delivery. The nanoparticle-based drug delivery systems has provided a solution to various drug solubility-related problems in ophthalmology treatment. Nanostructured compounds could be used to achieve local ocular delivery with minimal unwanted systematic side effects produced by taking advantage of the phagocyte system. In addition, the in vivo control release by nanomaterials encapsulated drugs provides prolong exposure of the compound in the body. Furthermore, certain nanoparticles can overcome important body barriers including the blood-retinal barrier as well as the corneal-retinal barrier of the eye for effective delivery of the drug. In summary, the nanotechnology based drug delivery system may serve as an important tool for uveal melanoma treatment.

Low-dose brachytherapy strategies to treat uveal melanoma: is less more?

The Collaborative Ocular Melanoma Study (COMS) has established equivalency of globe salvaging brachytherapy compared with enucleation in terms of survival for medium-sized choroidal melanoma. The radiation dose protocol followed by the COMS was 85 Gray to a prescription point of the tumor apex or 5 mm inner sclera; whichever was greater. While the COMS realized appropriate local and distant tumor control rates, ocular morbidity due to radiation complications remains a significant clinical challenge. Recent studies challenge the COMS radiation dose paradigm by demonstrating similar tumor control by utilizing lower radiation doses that are associated with reduced radiation toxicity. Improved operative techniques including intraoperative ultrasound can aid to obtain adequate radiation delivery to the tumor by ensuring optimal plaque position. Adjuvant transpupillary thermotherapy, intravitreal anti-VEGF and posterior sub-Tenon steroids may further enhance outcome by providing additional tumor control and/or facilitating visual recovery.

Use of Photosensitizers in Semisolid Formulations for Microbial Photodynamic Inactivation

Semisolid formulations, such as gels, creams and ointments, have recently contributed to the progression of photodynamic therapy (PDT) and microbial photodynamic inactivation (PDI) in clinical applications. The most important challenges facing this field are the physicochemical properties of photosensitizers (PSs), optimal drug release profiles, and the photosensitivity of surrounding tissues. By further integration of nanotechnology with semisolid formulations, very promising pharmaceuticals have been generated against several dermatological diseases (PDT) and (antibiotic-resistant) pathogenic microorganisms (PDI). This review focuses on the different PSs and their associated semisolid formulations currently found in both the market and clinical trials that are used in PDT/PDI. Special emphasis is placed on the advantages that the semisolid formulations bring to drug delivery in PDI. Lastly, some potential considerations for improvement in this field are also discussed.

Clinical use of photodynamic therapy in ocular tumors

Although the introduction of intravitreal anti-vascular endothelial growth factor drugs reduced the indications for photodynamic therapy in ophthalmology, it may still be used in various ocular tumors. Although many studies have shown that photodynamic therapy is effective in ocular tumors, the literature consists of case reports and series. In this review, we systematically performed a meta-analysis for the use of photodynamic therapy in circumscribed choroidal hemangioma, diffuse choroidal hemangioma, retinal capillary hemangioma, von Hippel-Lindau angiomatosis, choroidal melanoma, retinal astrocytoma, retinoblastoma, eyelid tumors, conjunctival tumors, and choroidal metastasis.

Photosensitizers in clinical PDT

Photosensitizers in photodynamic therapy allow for the transfer and translation of light energy into a type II chemical reaction. In clinical practice, photosensitizers arise from three families-porphyrins, chlorophylls, and dyes. All clinically successful photosensitizers have the ability to a greater or lesser degree, to target specific tissues or their vasculature to achieve ablation. Each photosensitizer needs to reliably activate at a high enough light wavelength useful for therapy. Their ability to fluoresce and visualize the lesion is a bonus. Photosensitizers developed from each family have unique properties that have so far been minimally clinically exploited. This review looks at the potential benefits and consequences of each major photosensitizer that has been tried in a clinical setting.

Current and emerging treatment options for uveal melanoma

Uveal melanoma (UM) is the most common primary malignant intraocular tumor in adults, with a 10-year cumulative metastatic rate of 34%. The most common site of metastasis is the liver (95%). Unfortunately, the current treatment of metastatic UM is limited by the lack of effective systemic therapy. Options for the management of the primary intraocular tumor include radical surgery as well as conservative treatments in order to preserve visual acuity. For metastatic disease, several approaches have been described with no standard method. Nevertheless, median survival after liver metastasis is poor, being around 4–6 months, with a 1-year survival of 10%–15%. In this review, the authors summarize current and promising new treatments for UM.

Clinical and histopathologic findings after photodynamic therapy of choroidal melanoma

BACKGROUND

Photodynamic therapy (PDT) has been used occasionally as an alternative treatment for uveal melanomas. The present study describes the clinical and histopathologic features of five choroidal melanomas after PDT.

METHODS

Three patients with pigmented choroidal melanomas were treated with PDT and intravitreal bevacizumab 1 week before undergoing biopsy and brachytherapy to minimize the risks of bleeding during the biopsy. Another two patients received PDT as a primary treatment for peripapillary amelanotic melanomas, one of them also in combination with bevacizumab.

RESULTS

The tumors treated with PDT and bevacizumab showed a marked reduction in tumor vascularity assessed by indocyanine angiography, and the biopsies were conducted without recognizable bleeding, showing viable tumor cells. The tumors receiving PDT as a primary treatment were followed by progressive tumor growth that led to enucleation years after. The histopathology revealed overlying fibrosis with invasion of sclera and optic nerve.

CONCLUSION

Photodynamic therapy and bevacizumab can induce closure of the superficial vasculature of a pigmented choroidal melanoma, but in none of our cases, there was evidence of tumor destruction from this treatment. Preoperative PDT may be useful to reduce the potential of bleeding at the time of tumor biopsy. Our cases do not support the use of a single session of PDT as a primary treatment for pigmented small choroidal melanomas.

Evaluation of verteporfin pharmakokinetics--redefining the need of photosensitizers in ophthalmology

INTRODUCTION

The benzoporphyrine derivative verteporfin has lost its importance to the treatment of the most frequent neovascular eye diseases. Nevertheless, it is still mandatory to define the remaining applications, role, and potential of verteporfin in ocular photodynamic therapy (PDT), including the dosages of administration, effectiveness, and safety profile.

AREAS COVERED

Although verteporfin PDT has forfeited the first-line status and value of treating subfoveal choroidal neovascularization (CNV) due to age-related macular degeneration or pathologic myopia, the treatment remains the standard of care for choroidal haemangioma and polypoidal choroidal vasculopathy. PDT is effective in less pigmented choroidal melanoma as well as in retinal vascular proliferations and retinal angioma. Verteporfin was granted the orphan drug designation for the treatment of chronic or recurrent central serous chorioretinopathy (CSC).

EXPERT OPINION

Evidence-based data regarding optimized parameters (low fluence, reduced dose, fractionated irradiation) adapted to the treated diseases (target structure, dosimetry, blood supply) are scarce. Prospective and large clinical trials are missing, although the scientific community agrees on the fact that the standard treatment protocol does not necessarily provide the optimal efficacy to the specific disease or individual patient. Within the reviewed indications, the adverse effect profile is favorable compared with other therapies.

Dramatic regression of amelanotic choroidal melanoma with PDT following poor response to brachytherapy

Photodynamic therapy (PDT) has been used for treatment of choroidal neovascular membrane from exudative macular degeneration. Other applications include treatment of some intraocular tumors, such as choroidal hemangioma, vasoproliferative tumor, and choroidal osteoma. The authors report the effect of PDT for amelanotic choroidal melanoma. A 40-year-old woman with an amelanotic choroidal melanoma of 6.5 mm thickness showed poor response to iodine brachytherapy (80 Gy apical dose) with no reduction in thickness at 16 months of follow-up. There was prominent residual tumor. The amelanotic tumor was treated with verteporfin PDT using three overlapping spots (8,600 microns), with avoidance of the optic disc using standard treatment parameters. Dramatic tumor regression over 2 months to a completely flat scar (1.3 mm thickness) was documented and remained stable at 50 months of follow-up. Amelanotic choroidal melanoma with incomplete response following conventional plaque radiotherapy can be treated with verteporfin PDT for consolidation.

Oncologic photodynamic therapy photosensitizers: a clinical review

A myriad of naturally occurring and synthetic structures are capable of transferring the energy of light. Few, however, allow for this energy transfer to enable a type II photochemical reaction which, as currently practiced, is a fundamental component of photodynamic therapy. Even fewer of these agents, aptly termed photosensitizers, have found success in the treatment of patients. This review will focus on the oncologic photosensitizers that have come to clinical trial with outcomes published in peer reviewed journals. Based on a clinical orientation the qualities of successful photosensitizers will be examined, how current drugs fare and potential future options explored.

Pharmacotherapy for the treatment of choroidal neovascularization due to age-related macular degeneration

Age-related macular degeneration (AMD) is a progressive, degenerative disease of the macula that threatens central vision. It initially occurs in a "dry" form, and can progress to choroidal neovascularization (CNV) or geographic atrophy. It is the leading cause of blindness among European-descended people older than 65 years, with a prevalence of 1.5%. The treatment of CNV in developed nations in 2007 is substantially different than it was in 1997. Focal, photocoagulating, laser therapy was replaced by intravenous verteporfin and then by intravitreal pegaptanib, which is now being replaced by intravitreal ranibizumab and off-label use of bevacizumab. Other than a ranibizumab versus verteporfin trial, there are no published comparative studies of the three approved pharmacological treatments for CNV. Although frequent intravitreal injections are accepted as a current standard of care, their use is still far from ideal. Thus, there is an opportunity for improving therapy of CNV with respect to mechanism-targeted treatments, efficacy, and route of administration.

Structural and physico-chemical determinants of the interactions of macrocyclic photosensitizers with cells

New therapies have been developed using reactive oxygen species produced by light-activation of photosensitizers (PS). Since the lifetime of these species is extremely short and their diffusion in space is limited, the photo-induced reactions primarily affect the cell organelles labeled by the PS. In addition to the development of molecules with the best optical and photosensitizing properties, considerable research has been done to understand the physico-chemical parameters governing their subcellular localization. In this review, we examine these parameters to establish the structure/efficacy relationships, which allow specific targeting of PS. We examine the effect of subcellular localization on the cellular response to photosensitization processes. We discuss the determinants of subcellular localization, including the hydrophobic/hydrophilic balance, the specific charge effects and the dynamics of PS' transfer through membranes. Specific targeting can also be achieved with molecular structures able to recognize cellular or intracellular receptors, and this is also dealt with in this paper.

Suspected uveal metastasis of a nail bed melanoma in a dog

A 13-year-old Golden Retriever was referred for evaluation of generalized corneal edema, dyscoria, and suspected glaucoma affecting the right eye. The dog exhibited no signs of systemic illness, but had a history of a melanoma of the nail bed of the first digit of the right hind limb, excised 1 year previously. Ophthalmologic examination revealed diffuse corneal edema, mild anterior uveitis, glaucoma and a mass within the right iris. Enucleation was performed and histopathologic evaluation of the globe revealed the iris to be infiltrated with an anaplastic melanoma, suspected to represent a metastasis of the original nail bed tumor.

Review of photodynamic therapy

INTRODUCTION

Photodynamic Therapy (PDT) is an emerging treatment for a variety of conditions including ocular and extra ocular diseases. The porphyrins have been used extensively, as dyes, which are laser-activated to achieve desired clinical effects. Commonly used agents are verteporfin and porfimer sodium.

METHODS

We performed a literature search of the PubMed database using the medical search headings: photodynamic therapy, photosensitizer verteporfin, visudyne, porfimer sodium and photofrin. We also performed a manual search using references from these articles, review articles and manufacturers' product monographs.

RESULTS

Verteporfin and porfimer sodium are commonly used photosensitizing agents with their wide applications in different fields of medicine. Both have well established safety profiles. They are most commonly used in wet age-related macular degeneration, gastrointestinal diseases and bronchial cancers.

CONCLUSION

PDT is a well established treatment entity in ophthalmology and other medical fields. In ophthalmology, it has rekindled interest and hopes in the common yet sight-threatening problem of age-related macular degeneration (AMD). This problem is still considered to be a serious issue as far as management is concerned. However in selective cases of AMD, it has shown success in restoring sight, especially in the 'classic' form of the disease. PDT is also being used to treat a range of solid cancers and non malignant conditions

Photodynamic treatment in a rabbit model of glaucoma surgery

PURPOSE

To evaluate the safety and efficacy of postoperative verteporfin photodynamic treatment as an adjunct to glaucoma experimental filtration surgery in rabbits.

METHODS

Dutch belted (n = 15) rabbits underwent full thickness sclerectomy in one eye. The experimental group (group 1, n = 7) underwent i.v. injection of verteporfin and subsequent photoactivation at the operative site on postoperative day 1 (POD 1). Control groups of animals received either light exposure (group 2, n = 4) or verteporfin (group 3, n = 2), or no intervention (group 4, n = 2). Intraocular pressure (IOP) was measured prior to the procedure (POD 0) and daily thereafter for the first week after sclerectomy (PODs 1-7) and every other day for the second week (PODs 9, 11, 13, 15). Percentage IOP reductions of operated over contralateral control eyes were compared among the various groups. Success rates (percentage IOP reduction > 15%) were also compared between the experimental and control groups. Eyes were histologically examined for evaluation of fibrosis.

RESULTS

Rabbits in the experimental group (group 1) had a mean +/- SEM percentage IOP reduction of 25 +/- 3% during the follow-up period. In contrast, groups 2, 3 and 4 had IOP reductions of 4 +/- 5%, 12 +/- 7% and 4 +/- 6%, respectively (p < 0.005, anova among all four groups). Successful IOP reduction (> or = 15%) over the contralateral eye at POD 15 was achieved in six of seven experimental animals, but only in one of eight control animals (p < 0.02, chi-squared test). Bleb failure occurred significantly earlier in the control eyes compared with eyes receiving PDT (p < 0.003, log rank test). Blebs in the experimental group differed from those in the control groups histologically, lacking significant collagen deposition in the area of the sclerostomy.

CONCLUSIONS

Wound healing in glaucoma surgery may be successfully modulated postoperatively using photodynamic therapy with i.v. administered photosensitizer.

The future of photodynamic therapy in oncology

The medicinal properties of light-based therapies have been appreciated for millennia. Yet, only in this century have we witnessed the birth of photodynamic therapy (PDT), which over the last few decades has emerged to prominence based on its promising results and clinical simplicity. The fundamental and distinguishing characteristics of PDT are based on the interaction of a photosensitizing agent, which, when activated by light, transfers its energy into an oxygen-dependent reaction. Clinically, this photodynamic reaction is cytotoxic and vasculotoxic. While the current age of PDT is based on oncological therapy, the future of PDT will probably show a significant expansion to non-oncological indications. This harks back to much of the original work from a century ago. Therefore, this paper will attempt to predict the future of PDT, based in part on a review of its origin.

Photodynamische Therapie mit Verteporfin beim Aderhautmelanom

BACKGROUND

The aim of this study was to evaluate whether photodynamic therapy (PDT) with verteporfin is able to induce tumor cell necrosis in human uveal melanomas.

METHODS

On four eyes with an uveal melanoma, PDT with verteporfin was performed on the tumor 2-3 days before planned enucleation. The eyes were evaluated histologically.

RESULTS

In two melanomas with only mild pigmentation some effects after PDT were detected on tumor tissue in a depth up to 2.5 mm at light doses > or =100 J/cm(2). Histologically, vascular occlusion and thrombosis in tumor vessels were observed. In the heavily pigmented melanoma no tumor necrosis was induced with the above-mentioned parameters.

CONCLUSION

Depending on treatment parameters and tumor pigmentation, PDT with verteporfin is able to induce tumor necrosis in human uveal melanomas. Based on these results it is possible that PDT can become an adjuvant treatment method for uveal melanoma.

Photodynamic therapy using Verteporfin (benzoporphyrin derivative monoacid ring A, BPD-MA) and 630 nm laser light in canine esophagus

BACKGROUND AND OBJECTIVE

Verteporfin is a new photosensitizer with short-term skin photosensitivity. The objective of this preclinical study was to find the light dose that effectively ablates canine esophageal mucosa when delivered 30 minutes after Verteporfin injection.

STUDY DESIGN/MATERIALS AND METHODS

Verteporfin was administered intravenously (0.75 mg/kg). 630 nm light from KTP/Dye laser was delivered using an esophageal Photodynamic therapy (PDT) balloon. In Phase I study, animals were treated 30 minutes after drug injection using 40, 60, and 80 J/cm to find the desired light dose. Using results from phase I and application of reciprocity principle (light dose vs. plasma concentration of drug), additional light doses were calculated for delivery at other times. In phase II, animals were treated at 15, 60, and 120 minutes, using the calculated light doses of 60, 145, and 200 J/cm, respectively. Animals were followed for 2 days to 4 weeks.

RESULTS

In Phase I, 80 J/cm at 30 minutes induced total mucosal ablation. In Phase II, light doses of 60, 145, and 200 J/cm induced similar mucosal injuries when delivered at 15, 60, and 120 minutes, respectively.

CONCLUSIONS

Effective mucosal ablation in canine esophagus was achieved using Verteporfin and 630 nm light doses of 60, 80, 145, and 200 J/cm when delivered at 15, 30, 60, and 120 minutes after the drug injection, respectively.

Treatment of presumed iris melanoma in dogs by diode laser photocoagulation: 23 cases

A semiconductor diode laser was used to cause remission of isolated presumed iris melanoma in 23 dogs. All cases presented as unilateral areas of raised iris hyperpigmentation, ranging in size from 2x 3 mm to 4x12 mm. Cases were treated using a diode laser delivery system through either an operating microscope adapter (OMA) or a laser indirect ophthalmoscope (LIO) with a 20D lens. Laser treatment was delivered 'to effect' using power ranging from 80 to 1000 mW and cumulative durations up to 14 min, 31 s (14:31). Immediate shrinkage of the mass was noted following treatment. Five cases required more than one laser treatment with three eyes receiving two treatments and two eyes receiving three treatments. Follow-up from the last laser treatment ranged from 6 months to 4.5 years during which time the lesions exhibited no enlargement. Minor complications related to laser treatment were seen, including: dyscoria, iris hyperpigmentation, and corneal edema due to collateral hyperthermia. Glaucoma and cataract formation were not observed. Non-invasive diode laser photocoagulation appears to be a safe and effective method of treatment for isolated, pigmented iris masses in dogs.

Photodynamic therapy in oncology

Photodynamic therapy (PDT) is a cancer treatment modality that is based on the administration of a photosensitiser, which is retained in tumour tissues more than in normal tissues, followed by illumination of the tumour with visible light in a wavelength range matching the absorption spectrum of the photosensitiser. The photosensitiser absorbs light energy and induces the production of reactive oxygen species in the tumour environment, generating a cascade of events that kills the tumour cells. The first generation photosensitiser, Photofrin (porfirmer sodium), has been approved for oesophageal and lung cancer in the US and has been under investigation for other malignant and non-malignant diseases. Sub-optimal light penetration at the treatment absorption peak of Photofrin and prolonged skin photosensitivity in patients are limiting factors for this preparation. Several new photosensitisers have improved properties, especially absorption of longer wavelength light which penetrates deeper into tissue and faster clearance from normal tissue. This paper reviews the current use of first- and second-generation photosensitisers in oncology. The use of PDT in oncology has been restricted to certain cancer indications and has not yet become an integral part of cancer treatment in general. The main advantage of PDT is that the treatment can be repeated multiple times safely, without producing immunosuppressive and myelosuppressive effects and can be administered even after surgery, chemotherapy or radiotherapy. The current work on new photosensitisers and light delivery equipment will address some of the present shortcomings of PDT. Much has been learned in recent years about the mechanisms of cellular and tissue responses to PDT and protocols designed to capitalise on this knowledge showed lead to additional improvements.

Photodynamic therapy in the treatment of subfoveal choroidal neovascularisation

Subfoveal choroidal neovascularisation (CNV) is a major cause of visual disability, with age-related macular degeneration (AMD) the commonest cause. Confluent laser to CNV significantly reduces severe visual loss but the profound visual loss after treatment of subfoveal lesions and the high recurrence rate has meant its restriction to extrafoveal lesions. Developed initially as a treatment for cancers, photodynamic therapy (PDT) has been shown to successfully close CNV in the eye. Large international randomised placebo-controlled studies of the safety and efficacy of PDT with verteporfin are under way. The Treatment of Age-related Macular Degeneration with Photodynamic Therapy (TAP) study has demonstrated a reduction of visual loss in treated patients with any classic CNV. Subgroup analysis showed a greater benefit in predominantly classic lesions (p < 0.001, NNT: 3.6), increasing further for lesions with no occult component, roughly equivalent to pure classic (p < 0.01, NNT: 2.2) A significant benefit at 12 months has been shown in patients with CNV secondary to myopia in the Verteporfin in AMD (VIP) trial, but no benefit in pure occult lesions. Further research is required to establish cost-effectiveness and appropriate referral patterns in the UK and optimise treatment strategies. Further data are awaited from TAP/VIP. At present verteporfin PDT is indicated in eyes with subfoveal predominantly classic CNV secondary to AMD with visual acuity of 6/60 or better and lesions < 5,400 microm in diameter. Juxtafoveal lesions meeting the above criteria and CNV secondary to pathological myopia should also be considered for treatment. The efficacy of treatment of larger lesions, juxtapapillary CNV, occult/no classic with high-risk characteristics (HRC) and CNV from other causes remains unclear. The treatment of minimally classic lesions and those with occult/no classic without HRC is not indicated.

Analysis of acute vascular damage after photodynamic therapy using benzoporphyrin derivative (BPD)

Benzoporphyrin derivative monoacid ring A (BPD-MA, verteporfin) is currently under investigation as a photosensitizer for photodynamic therapy (PDT). Since BPD exhibits rapid pharmacokinetics in plasma and tissues, we assessed damage to tumour and muscle microvasculature when light treatment for PDT was given at short times after injection of photosensitizer. Groups of rats with chondrosarcoma were given 2 mg kg(-1) of BPD intravenously 5 min to 180 min before light treatment of 150 J cm(-2) 690 nm. Vascular response was monitored using intravital microscopy and tumour cure was monitored by following regrowth over 42 days. For treatment at 5 or 30 min after BPD injection, blood flow stasis was limited to tumour microvasculature with lesser response in the surrounding normal microvasculature, indicating selective targeting for damage. No acute changes were observed in vessels when light was given 180 min after BPD injection. Tumour regression after light treatment occurred in all animals given PDT with BPD. Long-term tumour regression was greater in animals treated 5 min after BPD injection and least in animals given treatment 180 min after drug injection. The correlation between the timing for vascular damage and cure implies that blood flow stasis plays a significant role in PDT-induced tumour destruction.

Principles of treatment of choroidal neovascularization with photodynamic therapy in age-related macular degeneration

Age-related macular degeneration (AMD) is a common cause of legal blindness in the developed countries in people older than 50 years of age. AMD complicated by choroidal neovascular membranes (CNV) accounts for 12% of AMD, but for 88% of legal blindness cases. Because of the progressive aging of the population, it is expected that AMD will be one of the greater public health problems in ophthalmology in the first half of the next century. Laser photocoagulation remains the only proven treatment for CNV in AMD, but unfortunately, is applicable only to a minority of patients presenting with CNV in AMD. Photodynamic therapy (PDT) is a new experiment treatment for CNV that combines the application of low-intensity light with a photosensitizing agent in the presence of oxygen to produce tissue effects. It uses the noninvasive potential of the laser light to cause a nonthermal localized chemotoxic reaction and obtain highly selective occlusion of the neovascular channels, with sparing of the overlying photoreceptors. Animal studies showed that PDT accounts for the effective closure of experimentally induced CNV. Phase I-II clinical studies showed that PDT using BPD can safely stabilize leakage from CNV in a majority of patients for up to 3 months. Phase III clinical studies to assess the long term prognosis of PDT-treatment of CNV in AMD are ongoing.

Photodynamic therapy and digital angiography of experimental iris neovascularization using liposomal benzoporphyrin derivative

PURPOSE

To study the efficacy of liposomal benzoporphyrin derivative (BPD) (Verteportin) for the angiographic visualization and photodynamic therapy (PDT) of experimental iris neovascularization.

METHODS

Experimental iris neovascularization was induced in eight cynomolgus monkey eyes by occluding all the branch retinal veins with a dye-yellow (577-nm) laser. Iris angiography was done with sodium fluorescein, indocyanine green (ICG), and liposomal BPD to compare the visualization of normal and neovascular vessels by these three dyes. PDT was performed using an intravenous infusion of liposomal BPD (0.375-0.75 mg/kg), followed by irradiation with 689-nm light from a diode laser/slit-lamp delivery system using 600 mW/cm2 irradiance and 150 J/cm2 fluence. The effect of treatment was followed by iris photography and angiography, and the findings were confirmed by histopathology using light and electron microscopy.

RESULTS

Iris fluorescein angiography (FA) showed superficial tortuous and leaky new vessels. Liposomal BPD and ICG angiography of the same eye demonstrated deeper dilated and tortuous iris vessels, with minimal dye leakage. PDT of the iris with irradiation, performed within 20 minutes of the start of dye infusion (0.75 mg/kg), resulted in angiographic and histologic occlusion of iris vessels examined at 24 hours. Three to nine days after PDT, histopathologic examination showed regression of the iris neovascular membrane, with some open vessels.

CONCLUSIONS

Liposomal BPD and ICG provided angiographic visualization of deeper normal and neovascular iris vessels. PDT using liposomal BPD leads to effective early closure to experimental iris neovascularization.

Photodynamic therapy of pigmented choroidal melanomas of greater than 3-mm thickness

PURPOSE

The purpose of the study is to determine the effect of photodynamic therapy in the destruction of experimental pigmented choroidal melanomas > or = 3 mm in thickness using a liposomal preparation of benzoporphyrin derivative, verteporfin.

METHODS

Pigmented choroidal tumors were established in 32 New Zealand albino rabbit eyes. Animals were treated with daily injections of cyclosporine, and tumor growth was followed by serial fundus examinations and ultrasonography. When a tumor exceeded 3 mm in thickness (tumor height ranged from 3.1-4.6 mm), the authors administered benzoporphyrin derivative intravenously (1 mg/kg) and irradiated the tumor at 692-nm through an argon-pumped dye laser at different total light doses ranging from 60 to 120 J/cm2. Control animals were treated with light or benzoporphyrin derivative only. Each animal then was followed-up for 4 to 6 weeks by fundus photography, fluorescein angiography, and ultrasonography.

RESULTS

All animals treated with benzoporphyrin derivative and light at fluences of > or = 80 J/cm2 showed complete tumor arrest. In contrast, both control groups showed continuous tumor growth in all animals with tumors filling most of the vitreous cavity by 3 weeks. Histologic examination results of tumors treated with dye plus light immediately after treatment showed prominent vascular closure. No vascular changes were noted in the control eye treated with light or dye alone. Examination results of the eyes that showed tumor regression after a 4-week follow-up period showed tumor necrosis and extensive infiltration of mononuclear cells and pigment-laden macrophages at the tumor site.

CONCLUSIONS

These data suggest that photodynamic therapy may have a role in the management of pigmented choroidal melanomas.