Photodynamic therapy for cancer of the upper aerodigestive tract using tetra(m-hydroxyphenyl)chlorin

Endoscope Capsules: The Present Situation and Future Outlooks

This paper presents new perspectives on photonic technologies for capsule endoscopy. It first presents a review of conventional endoscopy (upper endoscopy and colonoscopy), followed by capsule endoscopy (CE), as well as their techniques, advantages, and drawbacks. The technologies for CEs presented in this paper include integration with the existing endoscopic systems that are commercially available. Such technologies include narrow-band imaging (NBI), photodynamic therapy (PDT), confocal laser endomicroscopy (CLE), optical coherence tomography (OCT), and spectroscopy in order to improve the performance of the gastrointestinal (GI) tract examination. In the context of NBI, two optical filters were designed and fabricated for integration into endoscopic capsules, allowing for the visualization of light centered at the 415 nm and 540 nm wavelengths. These optical filters are based on the principle of Fabry-Perot and were made of thin films of titanium dioxide (TiO2) and silicon dioxide (SiO2). Moreover, strategies and solutions for the adaptation of ECs for PDT are also discussed.

Reactive Oxygen Species Produced by 5-Aminolevulinic Acid Photodynamic Therapy in the Treatment of Cancer

Cancer is the leading cause of death worldwide and several anticancer therapies take advantage of the ability of reactive oxygen species to kill cancer cells. Added to this is the ancient hypothesis that light alone can be used to kill cancer cells. 5-aminolevulinic acid-photodynamic therapy (5-ALA-PDT) is a therapeutic option for a variety of cutaneous and internal malignancies. PDT uses a photosensitizer that, activated by light in the presence of molecule oxygen, forms ROS, which are responsible for the apoptotic activity of the malignant tissues. 5-ALA is usually used as an endogenous pro-photosensitizer because it is converted to Protoporphyrin IX (PpIX), which enters into the process of heme synthesis and contextually becomes a photosensitizer, radiating a red fluorescent light. In cancer cells, the lack of the ferrochelatase enzyme leads to an accumulation of PpIX and consequently to an increased production of ROS. PDT has the benefit of being administered before or after chemotherapy, radiation, or surgery, without impairing the efficacy of these treatment techniques. Furthermore, sensitivity to PDT is unaffected by the negative effects of chemotherapy or radiation. This review focuses on the studies done so far on 5-ALA-PDT and its efficacy in the treatment of various cancer pathologies.

J, M.D.P. DE. C, RAJENDRAM S. Photodynamic Therapy : An Overview and Insights into a Prospective Mainstream Anticancer Therapy

Photodynamic therapy (PDT) procedure has minimum invasiveness in contrast to conventional anticancer surgical procedures. Although clinically approved a few decades ago, it is not commonly used due to its poor efficacy, mainly due to poor light penetration into deeper tissues. PDT uses a photosensitizer (PS), which is photoactivated on illumination by light of appropriate wavelength and oxygen in the tissue, leading to a series of photochemical reactions producing reactive oxygen species (ROS) triggering various mechanisms resulting in lethal effects on tumor cells. This review looks into the fundamental aspects of PDT, such as photochemistry, photobiological effects, and the current clinical applications in the light of improving PDT to become a mainstream therapeutic procedure against a broad spectrum of cancers and malignant lesions. The side effects of PDT, both early and late-onset, are elaborated on in detail to highlight the available options to minimize side effects without compromising therapeutic efficacy. This paper summarizes the benefits, drawbacks, and limitations of photodynamic therapy along with the recent attempts to achieve improved therapeutic efficacy via monitoring various cellular and molecular processes through fluorescent imagery aided by suitable biomarkers, prospective nanotechnology-based targeted delivery methods, the use of scintillating nanoparticles to deliver light to remote locations and also combining PDT with conventional anticancer therapies have opened up new dimensions for PDT in treating cancers. This review inquires and critically analyses prospective avenues in which a breakthrough would finally enable PDT to be integrated into mainstream anticancer therapy.

Photodynamic Therapy in Dentistry

Photodynamic therapy (PDT), also known as photoradiation therapy, phototherapy, or photochemo-therapy, involves the use of a photoactive dye (photosensitizer) that is activated by exposure to light of a specific wavelength in the presence of oxygen. The transfer of energy from the activated photosensitizer to available oxygen results in the formation of toxic oxygen species, such as singlet oxygen and free radicals. These very reactive chemical species can damage proteins, lipids, nucleic acids, and other cellular components. Applications of PDT in dentistry are growing rapidly: the treatment of oral cancer, bacterial and fungal infection therapies, and the photodynamic diagnosis (PDD) of the malignant transformation of oral lesions. PDT has shown potential in the treatment of oral leukoplakia, oral lichen planus, and head and neck cancer. Photodynamic antimicrobial chemotherapy (PACT) has been efficacious in the treatment of bacterial, fungal, parasitic, and viral infections. The absence of genotoxic and mutagenic effects of PDT is an important factor for long-term safety during treatment. PDT also represents a novel therapeutic approach in the management of oral biofilms. Disruption of plaque structure has important consequences for homeostasis within the biofilm. Studies are now leading toward selective photosensitizers, since killing the entire flora leaves patients open to opportunistic infections. Dentists deal with oral infections on a regular basis. The oral cavity is especially suitable for PACT, because it is relatively accessible to illumination.

Photodynamic therapy in the upper aerodigestive tract. Overview and outlook

The gold standard in the treatment of (pre)malignancies of the upper aerodigestive tract (UADT) is either surgery or (chemo)radiotherapy. Nevertheless, there are special indications where an alternative treatment, such as photodynamic therapy (PDT), might be as effective for and better tolerated by the patients concerned. This article aims to present a contemporary and comprehensive review on the role of photodynamic therapy in the treatment of (pre)malignancies of the UADT. PubMed was searched for "photodynamic therapy larynx/oral cavity/oropharynx/head and neck" in 01/2016. PDT can be efficient in the treatment of recurrent, residual or multiple carcinomas of the UADT without other treatment options. It has also been used with success in the treatment of early oral or laryngeal carcinomas, widespread precancerous lesions or "difficult-to-treat" skin cancer, even though these treatments are off-label. For now, unsolved scientific and economical challenges hinder the methods spread. In special cases, PDT is a highly effective method to treat head and neck (pre)malignancies. Nevertheless, further clinical studies are needed to better define its true value in head and neck oncology.

Antibody-based imaging strategies for cancer

Although mainly developed for preclinical research and therapeutic use, antibodies have high antigen specificity, which can be used as a courier to selectively deliver a diagnostic probe or therapeutic agent to cancer. It is generally accepted that the optimal antigen for imaging will depend on both the expression in the tumor relative to normal tissue and the homogeneity of expression throughout the tumor mass and between patients. For the purpose of diagnostic imaging, novel antibodies can be developed to target antigens for disease detection, or current FDA-approved antibodies can be repurposed with the covalent addition of an imaging probe. Reuse of therapeutic antibodies for diagnostic purposes reduces translational costs since the safety profile of the antibody is well defined and the agent is already available under conditions suitable for human use. In this review, we will explore a wide range of antibodies and imaging modalities that are being translated to the clinic for cancer identification and surgical treatment.

Preclinical validation of talaporfin sodium-mediated photodynamic therapy for esophageal squamous cell carcinoma

Photodynamic therapy (PDT) kills cancer cells via a photochemical reaction mediated by an oncotropic photosensitizer. Herein, we performed an experimental preclinical study to validate the anti-tumour effect of talaporfin sodium-mediated PDT (t-PDT) for esophageal squamous cell carcinoma (ESCC) cells. We used human ESCC cells derived from various differentiation grades or resistant to 5-fluorouracil (5-FU). The cytotoxic effect of t-PDT was determined by evaluating cell viability, apoptosis and generation of reactive oxygen species (ROS) and DNA double-strand breaks. Furthermore, the anti-tumour effect of t-PDT was assessed using an anchorage-independent cell-growth assay and xenograft transplantation models. t-PDT induced potent cytotoxicity in ESCC cells independent of their differentiation grade or 5-FU resistance. Moreover, t-PDT induced robust apoptosis, as indicated by cell shrinkage, perinuclear vacuolization, nuclear fragmentation and induction of annexin V-positive cells. This apoptotic response was accompanied by concurrent activation of ROS, and induction of DNA double-strand breakage. Importantly, t-PDT suppressed efficiently anchorage-independent cell growth as well as ESCC-xenografted tumor formation. In aggregate, t-PDT showed anti-tumor potential for ESCC cells with various histological grades or chemoresistance, providing a novel translational rationale of t-PDT for the treatment of ESCC.

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.

Enhanced antitumor activity of the photosensitizer meso-Tetra(N-methyl-4-pyridyl) porphine tetra tosylate through encapsulation in antibody-targeted chitosan/alginate nanoparticles

meso-Tetra(N-methyl-4-pyridyl) porphine tetra tosylate (TMP) is a photosensitizer that can be used in photodynamic therapy (PDT) to induce cell death through generation of reactive oxygen species in targeted tumor cells. However, TMP is highly hydrophilic, and therefore, its ability to accumulate intracellularly is limited. In this study, a strategy to improve TMP uptake into cells has been investigated by encapsulating the compound in a hydrogel-based chitosan/alginate nanoparticle formulation. Nanoparticles of 560 nm in diameter entrapping 9.1 μg of TMP per mg of formulation were produced and examined in cell-based assays. These particles were endocytosed into human colorectal carcinoma HCT116 cells and elicited a more potent photocytotoxic effect than free drug. Antibodies targeting death receptor 5 (DR5), a cell surface apoptosis-inducing receptor up-regulated in various types of cancer and found on HCT116 cells, were then conjugated onto the particles. The conjugated antibodies further enhanced uptake and cytotoxic potency of the nanoparticle. Taken together, these results show that antibody-conjugated chitosan/alginate nanoparticles significantly enhanced the therapeutic effectiveness of entrapped TMP. This novel approach provides a strategy for providing targeted site-specific delivery of TMP and other photosensitizer drugs to treat colorectal tumors using PDT.

mTHPC mediated photodynamic therapy (PDT) of squamous cell carcinoma in the head and neck: a systematic review

OBJECTIVE

Photodynamic therapy (PDT) is used in curative and palliative treatment of head and neck squamous cell carcinoma (HNSCC). To evaluate available evidence on the use of mTHPC (Foscan®) mediated PDT, we conducted a review of the literature.

MATERIALS AND METHODS

A systematic review was performed by searching seven bibliographic databases on database specific mesh terms and free text words in the categories; "head and neck neoplasms", "Photodynamic Therapy" and "Foscan". Papers identified were assessed on several criteria by two independent reviewers.

RESULTS

The search identified 566 unique papers. Twelve studies were included for our review. Six studies reported PDT with curative intent and six studies reported PDT with palliative intent, of which three studies used interstitial PDT. The studies did not compare PDT to other treatments and none exceeded level 3 using the Oxford levels of evidence. Pooling of data (n=301) was possible for four of the six studies with curative intent. T1 tumors showed higher complete response rates compared to T2 (86% vs 63%). PDT with palliative intent was predominantly used in patients unsuitable for further conventional treatment. After PDT, substantial tumor response and increase in quality of life was observed. Complications of PDT were mostly related to non-compliance to light restriction guidelines.

CONCLUSION

The studies on mTHPC mediated PDT for HNSCC are not sufficient for adequate assessment of the efficacy for curative intent. To assess efficacy of PDT with curative intent, high quality comparative, randomized studies are needed. Palliative treatment with PDT seems to increase the quality of life in otherwise untreatable patients.

Pharmaceutical development and medical applications of porphyrin-type macrocycles

The current state of pharmaceutical development of porphyrin-type macrocycles in medicine is highlighted. Currently, several porphyrinoid-based drugs are under various stages of development as phototherapeutic agents, X-ray radiation enhancers and boron neutron capture agents. These compounds represent a burgeoning class of pharmacological agents that are potentially useful in an array of treatment areas.

Temoporfin (Foscan®, 5,10,15,20-tetra(m-hydroxyphenyl)chlorin)--a second-generation photosensitizer

This review traces the development and study of the second-generation photosensitizer 5,10,15,20-tetra(m-hydroxyphenyl)chlorin through to its acceptance and clinical use in modern photodynamic (cancer) therapy. The literature has been covered up to early 2011.

The safety and effectiveness of endoscopic and non-endoscopic approaches to the management of early esophageal cancer: a systematic review

INTRODUCTION

Traditionally, management of early cancer (stages 0-IIA) has comprised esophagectomy, either alone or in combination with chemotherapy and/or radiotherapy. Recent efforts to improve outcomes and minimize side-effects have focussed on minimally invasive, endoscopic treatments that remove lesions while sparing healthy tissue. This review assesses their safety and efficacy/effectiveness relative to traditional, non-endoscopic treatments for early esophageal cancer.

METHODS

A systematic review of peer-reviewed studies was performed using Cochrane guidelines. Bibliographic databases searched to identify relevant English language studies published in the last 3 years included: PubMed (i.e., MEDLINE and additional sources), EMBASE, CINAHL, The Cochrane Library, the UK Centre for Reviews and Dissemination (NHS EED, DARE and HTA) databases, EconLit and Web of Science. Web sites of professional associations, relevant cancer organizations, clinical practice guidelines, and clinical trials were also searched. Two independent reviewers selected, critically appraised, and extracted information from studies.

RESULTS

The review included 75 studies spanning 3124 patients and 10 forms of treatment. Most studies were of short term duration and non-comparative. Adverse events reported across studies of endoscopic techniques were similar and less significant compared to those in the studies of non-endoscopic techniques. Complete response rates were slightly lower for photodynamic therapy (PDT) relative to the other endoscopic techniques, possibly due to differences in patient populations across studies. No studies compared overall or cause-specific survival in patients who received endoscopic treatments vs. those who received non-endoscopic treatments.

DISCUSSION

Based on findings from this review, there is no single "best practice" approach to the treatment of early esophageal cancer.

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.

Outcome of photodynamic therapy for early esophageal cancer

BACKGROUND/AIMS

Endoscopic treatment as an alternative to surgery has become increasingly popular for improving the quality of life. Although photodynamic therapy (PDT) has been used for the endoscopic treatment of digestive cancer, its curative efficacy remains unclear. We evaluated the curative efficacy of PDT in superficial esophageal cancer in inoperable patients.

METHODS

Ten male patients with histologically proven early esophageal cancer (surgery was contraindicated for age > 80 years, surgery was contraindicated, Karnofsky performance status of at least 30%, or refusal of surgery) were intravenously injected with a hematoporphyrin derivative (2 mg/kg), and PDT was performed 48 h later. The response to treatment was assessed by gastroscopy with biopsies.

RESULTS

The mean follow-up period was 27.6 months (range, 9.6-58.7 months). Endoscopic ultrasonography revealed that all ten cases were at tumor stage T1. Complete remission (CR) to initial and subsequent PDT was observed in all patients. For the CR cases, the recurrence rate was 10% (1/10) and the time from initial PDT to recurrence was 9.6 months.

CONCLUSIONS

For patients in whom surgery is risky or refused, PDT may represent an acceptable alternative treatment modality, especially for superficial esophageal cancer without lymph node metastasis. However, a study involving long-term follow-up in a large population is needed for confirmation.

m-THPC-mediated photodynamic therapy of malignant gliomas: assessment of a new transfection strategy

Malignant gliomas represent the most common primary brain tumor: more than 50% of them are glioblastoma multiforme (GBM). Photodynamic therapy may offer a very good chance of targeted destruction of infiltrating GBM cells, thus increasing the survival time and recurrence-free interval of GBM patients. Among photosensitizing agents, meta-tetrahydroxyphenylchlorin (m-THPC) is promising for the treatment of brain tumors. In previous studies, we investigated the transfection activity of dimyristoyl-sn-glycero-phosphatidylcholine (DMPC) liposomes, containing a cationic gemini surfactant, loaded with m-THPC on human colon adenocarcinoma and glioblastoma cell lines. In this paper, the uptake and the intracellular distribution of m-THPC, loaded in several formulations of cationic liposomes, were analyzed, by making a comparison with those obtained using the same chlorin in the pharmaceutical form (Foscan(R)). Moreover, by cloning efficiency assay the potential therapeutic efficiency of chlorin delivered by liposome formulations was compared with that of the pharmaceutical compound, before and after irradiation with laser light at 652 nm. The obtained results indicated that cationic liposomes (i) transferred m-THPC in glioblastoma cells more efficiently than pharmaceutical formulation; (ii) significantly (p < 0.001) increased the m-THPC cytotoxic effect after laser irradiation; (iii) seemed to exert their cytotoxic action in the early phase of interaction with the cells, during adhesion to the plasma membrane.

Photodynamic therapy of age-related macular degeneration: History and principles

We briefly review the history and principles of photodynamic therapy (PDT), especially as it is applied to choroidal neovascularization (CNV) in age-related macular degeneration (AMD). After a brief general history of PDT, we discuss the relationship between the physicochemical structure and photodynamic activity of the second-generation photosensitizers, such as those in current clinical use. We then discuss the basic photophysics of photosensitizer molecules, and describe the initial chemical reactions induced by activated sensitizers. We outline a novel method for screening photosensitizers to be used in treating CNV, as well as the complex biomolecular pathways modulated by PDT-induced oxidative stress and the vascular effects of PDT in solid tumors. The paper closes with a discussion of how all this information might be used to improve the selectivity and efficacy of clinically useful photosensitizers.

Photodynamic Therapy in Oncology

Photodynamic therapy (PDT) is increasingly being recognized as an attractive, alternative treatment modality for superficial cancer. Treatment consists of two relatively simple procedures: the administration of a photosensitive drug and illumination of the tumor to activate the drug. Efficacy is high for small superficial tumors and, except for temporary skin photosensitization, there are no long-term side effects if appropriate protocols are followed. Healing occurs with little or no scarring and the procedure can be repeated without cumulative toxicity. Considering the efficacy and lack of long-term toxicity of PDT, and the fact that the first treatment of cancer with PDT was done more than 100 years ago, one might expect that this treatment had already become an established therapy. However, PDT is currently offered in only a few selected centers, although it is slowly gaining acceptance as an alternative to conventional cancer therapies. Here, we show the developmental steps PDT underwent and summarize the current clinical applications. The data show that, when properly used, PDT is an effective alternative treatment option in oncology.

Cationic liposomes, loaded with m-THPC, in photodynamic therapy for malignant glioma

In this study we investigated the feasibility of mixed liposomes formed by dimyristoyl-sn-glycero-phosphatidylcholine (DMPC) and cationic gemini surfactant (Gemini 1) loaded with the chlorin m-tetrahydroxyphenylchlorin (m-THPC), in photodynamic therapy (PDT) for glioma. To this aim, an in vitro study was carried out by employing various human glioblastoma cell lines (A172, DBTRG, LN229, U118). The following liposomal formulations were tested: (i) DMPC and Gemini 1; (ii) m-THPC in DMPC in the absence or (iii) in the presence of Gemini 1 in the molar ratio 8:2; 7:3, and 6:4. The presence of Gemini 1 significantly increased the intracellular uptake of chlorin in all cell tested although with a different extent: LN229>U118>A172>DBTRG. The cytotoxicity of chlorin-loaded liposomes was then tested by cloning efficiency performed on different cultures, before and after irradiation with laser light at 652nm, at a Fluence Rate of 200mW/s for 100s, with a total Fluence of 20J/cm(-2). In the absence of irradiation, the different liposomal formulations induced a cytotoxicity in less than 30% of glioblastoma cells. On the contrary, irradiation induced total destruction of all cultures treated with m-THPC/DMPC+Gemini 1 in the ratios 8:2, or 7:3, or 6:4.

Photodynamic therapy of cerebral glioma – A review Part II – Clinical studies

Photodynamic therapy (PDT) is a binary treatment modality that has been used to treat malignant brain tumours for 25 years. The treatment involves the selective uptake of a photosensitizer (PS) by the tumour cells followed by irradiation of the tumour with light of the appropriate wavelength to excite and activate the PS resulting in selective tumour destruction and is a potentially valuable adjunct to surgical excision and other conventional therapies. PDT has undergone extensive laboratory studies and clinical trials with a variety of PS and tumour models. These are discussed with reference mainly to clinical studies involving the PDT of brain tumours.

Clinical photodynamic therapy of head and neck cancers-A review of applications and outcomes

As local control is tantamount to cure in head and neck cancer, an aggressive regimen of surgery and radiation remains the standard of care for most patients. Despite significant technical advances, these treatments are highly morbid. Further, patients who fail treatment have limited salvage options. Photodynamic therapy (PDT) and photodiagnosis (PD) of head and neck cancer offer significant potential for improved outcomes in a myriad of clinical indications ranging from in situ to recurrent disease. However, despite promising results, these modalities remain at the fringe of head and neck treatment options. Photofrin(®), Photosan and Foscan(®) are photosensitizers used clinically in head and neck PD/PDT. In addition, aminolevulinic acid (ALA), which gives origin to Protoporphyrin IX, an endogeneous photosensitizer, is also used for PD/PDT. We review the clinical literature on these photosensitizers to assist in the integration of these important modalities into the mainstream of head and neck oncological therapy.

Cost-effectiveness of photodynamic therapy for high-grade dysplasia in Barrett's esophagus

BACKGROUND

Photodynamic therapy appears to be effective in ablating high-grade dysplasia in Barrett's esophagus. Our aim was to identify the most effective and cost-effective strategy for managing high-grade dysplasia in Barrett's esophagus without associated endoscopically visible abnormalities.

METHODS

By using decision analysis, the lifetime costs and benefits of 4 strategies for which long-term data exist were estimated by us: esophagectomy, endoscopic surveillance, photodynamic therapy, followed by esophagectomy for residual high-grade dysplasia; and photodynamic therapy followed by endoscopic surveillance for residual high-grade dysplasia. It was assumed by us that there was a 30% prevalence of cancer in high-grade dysplasia patients and a 77% efficacy of photodynamic therapy for high-grade dysplasia and early cancer.

RESULTS

Esophagectomy cost 24,045 dollars, with life expectancy of 11.82 quality-adjusted life years. In comparison, photodynamic therapy followed by surveillance for residual high-grade dysplasia was the most effective strategy, with a quality-adjusted life expectancy of 12.31 quality-adjusted life years, but it also incurred the greatest lifetime cost (47,310 dollars) for an incremental cost-effectiveness of 47,410 dollars/quality-adjusted life years. The results were sensitive to post-surgical quality of life and survival, and to cancer prevalence if photodynamic therapy efficacy for cancer was less than 50%.

CONCLUSIONS

Photodynamic therapy followed by endoscopic surveillance for residual high-grade dysplasia appears to be cost effective compared with esophagectomy for patients diagnosed with high-grade dysplasia in Barrett's esophagus. Clinical trials directly comparing these strategies are warranted.

Time-dependent hexaminolaevulinate induced protoporphyrin IX distribution after topical application in patients with cervical intraepithelial neoplasia: A fluorescence microscopy study

BACKGROUND AND OBJECTIVES

Compared to the conventional management of cervical intraepithelial neoplasia (CIN) the potential advantage of photodynamic therapy (PDT) for the treatment of cervical human papilloma virus (HPV)-related disease encompasses a minimal invasive procedure with reduced risk of profuse bleeding as a consequence of conization, and possibly more favorable long-term results avoiding cervical stenosis. At present little is known about the precise time-dependent distribution and histological localization of hexaminolaevulinate (HAL) induced protoporphyrin IX (PPIX) fluorescence in healthy tissue and in CIN. The aim of this study was to use ex vivo fluorescence microscopy to determine whether PPIX is selectively induced by neoplastic cells of the cervical epithelium at various times after topical application.

STUDY DESIGN/MATERIALS AND METHODS

Cold cream containing 0.5% HAL was applied by means of cervical cap over various periods of time. We analyzed 52 healthy cervical mucosa and 84 CINs.

RESULTS

At time delay 100 (+/-10) minutes, high epithelial fluorescence and a significant selectivity between epithelium and underlying lamina propria was found. By contrast, no significant difference between healthy and neoplastic tissues, or between low and high-grade epithelial dysplasia (P > or = 0.05), was observed at any time point.

CONCLUSIONS

Application of HAL 0.5% cream to the cervix induced selective fluorescence in epithelial cells. The optimal ratio with a homogeneous PPIX distribution was obtained after 100 ( +/- 10) minutes cream application, which should be evaluated further for PDT.

Photodynamic therapy with green light and m-tetrahydroxyphenyl chlorin for intramucosal adenocarcinoma and high-grade dysplasia in Barrett's esophagus

BACKGROUND

The eradication of early stage neoplastic lesions in Barrett's esophagus is imperative to prevent invasive adenocarcinoma. Early stage lesions have an extremely low risk of lymph node metastasis, thereby, making local treatment feasible. Photodynamic therapy destroys malignant cells by a photochemical effect. The aims of this study were to evaluate the efficacy and tolerance of photodynamic therapy with green light and a new photosensitizer, temoporfin or m-tetrahydroxyphenyl chlorin in patients with Barrett's esophagus and early stage neoplastic lesions.

METHODS

Four days after injection of m-tetrahydroxyphenyl chlorin, lesions were illuminated at a wavelength of 514 nm through non-circumferential windowed diffusers. Follow-up endoscopy with biopsies was performed at regular intervals.

RESULTS

Fourteen lesions (7 high-grade dysplasia, 7 intramucosal adenocarcinoma) in 12 patients were treated. For all lesions, efficacy was 100% and squamous re-epithelialization was complete. Side effects were of moderate severity (one stricture). Mean follow-up was 34 (15) months (range 12-68 months).

CONCLUSIONS

Green light photodynamic therapy with m-tetrahydroxyphenyl chlorin can eradicate early stage neoplastic lesions in Barrett's esophagus and may be proposed as an alternative first-line therapy or a second-line therapy after failure of other endoscopic treatments. The efficacy and patient tolerance of the procedure justify further studies of the method in larger groups of patients.

Selectivity of the photosensitiser Tookad for photodynamic therapy evaluated in the Syrian golden hamster cheek pouch tumour model

The response to photodynamic therapy (PDT) with the photosensitiser (PS) Tookad® was measured in the Syrian hamster cheek pouch model on normal mucosae and chemically induced squamous cell carcinoma. This PS is a palladium-bacteriopheophorbide presenting absorption peaks at 538 and 762 nm. The light dose, drug dose and drug injection-light irradiation times (DLI), ranging between 100 and 300 J cm⁻², 1–5 mg kg⁻¹ and 10–240 min respectively, were varied and the response to PDT was analysed by staging the macroscopic response and by the histological examination of the sections of the irradiated cheek pouch. A fast time decay of the tissular response with drug dose of 1–5 mg kg⁻¹ was observed for DLI ranging from 10 to 240 min and for light doses of 100–300 J cm⁻² delivered at a light dose rate of 150 mW cm⁻². A significantly higher level of tissular response was observed for squamous cell carcinoma compared to normal tissue. Nevertheless, the threshold level of the drug–light dose for a detectable response was not significantly different in the tumoral vs normal tissue. The highest response at the shortest DLIs and the absence of measurable response at DLI larger than 240 min at light dose of 300 J cm⁻² and drug dose of 5 mg kg⁻¹ reveals the predominantly vascular effect of Tookad®. This observation suggests that Tookad® could be effective in PDT of vascularised lesions.

Evaluation of the photosensitizer Tookad for photodynamic therapy on the Syrian golden hamster cheek pouch model: light dose, drug dose and drug-light interval effects

We have evaluated the efficacy of the new photosensitizer (PS) Tookad in photodynamic therapy (PDT) in vivo. This PS is a palladium-bacteriopheophorbide presenting absorption peaks at 762 and 538 nm. The light dose, drug dose and drug injection-light irradiation interval (DLI), ranging between 100 and 300 J/cm2, 1 and 5 mg/kg and from 10 to 240 min, respectively, were varied, and the response to PDT was analyzed by staging the macroscopic response and by the histological examination of the sections of the irradiated cheek pouch. The level of PDT response, macroscopically and histologically, shows a strong dependence on the DLI, light dose and drug dose at the applied conditions in the normal hamster cheek pouch. A decay of the tissular response with increasing DLI is observed corresponding to a time of half-maximum response ranging from 10 to 120 min, depending on drug dose and light dose. The tissues affected at the lowest doses are predominantly the vascularized diffuse connective tissue situated between the inner and outer striated muscle (SM) layers as well as these muscle layers themselves. The highest response at the shortest DLI and the absence of a measurable response at DLI longer than 240 min at 300 J/cm2 and drug dose of 5 mg/kg are characteristics of a predominantly vascular effect of this PS. This observation suggests that Tookad could be effective in PDT of vascularized lesions or pathologies associated with the proliferation of neovessels.

Photodynamic therapy with chlorin e6 for skin metastases of melanoma

BACKGROUND

Photodynamic therapy (PDT) has been successfully applied in clinical settings to destroy neoplasms, but the efficacy of such a treatment is dependent on the type of neoplasm and the photosynthesizer used. Here, we perform a clinical assessment of PDT for skin metastases of pigmented melanoma using chlorin e(6).

STUDY DESIGN/MATERIALS AND METHODS

PDT with chlorin e(6) photosensitizer was administered to 14 patients with skin metastases from melanoma (10 females, four males, mean age 49.6 years). Chlorin e(6) at a dose of 5 mg/kg of patient's weight was intravenously injected. The treatment course consisted of two courses of PDT exposure 1 h after intravenous chlorin e(6) injection and 24 h post-injection. The light energy density for each skin tumor was 80-120 J/cm(2) per treatment, with a light power density of 250-300 mW/cm(2).

RESULTS

All skin melanoma metastases that received PDT showed complete regression with no recurrence during the study period. The complete response of all skin metastases from melanoma occurred in eight cases after one PDT treatment. In the remaining six individuals, tumors required multiple PDT courses prior to complete regression. No cases of photodermatitis were registered. The Karnofsky performance scale score of the patients with skin metastases from melanoma showed no significant difference before and after PDT. No patients had significant changes in blood cell counts that would indicate chlorin e(6) systemic toxic effect. Blood chemistry and urinalysis did not show any evidence of chlorin e(6) renal and hepatic injury.

CONCLUSIONS

PDT with chlorin e(6) for skin metastases from melanoma is effective and well tolerated. Further clinical investigation of PDT with chlorin e(6) is warranted.

Mucosal ablation with photodynamic therapy in the esophagus: optimization of light dosimetry in the sheep model

BACKGROUND

Photodynamic therapy is an attractive technique for mucosal ablation in patients with superficial squamous cell carcinoma of the esophagus, or high-grade dysplasia or early stage adenocarcinoma arising in Barrett's esophagus. Although illumination with green light is assumed to be safe, choice of the light has been empirical in clinical studies; light dose is often reduced to avoid potential complications. The present study assessed the safety of green and blue lights during photodynamic therapy in the esophagus by progressively administrating increasing doses in an attempt to standardize the dose and determine a safe upper limit. This would considerably simplify photodynamic therapy and improve therapeutic results.

METHODS

The sheep model was chosen because of similarities with humans regarding the thickness and histologic structure of the esophagus. Irradiation with a 180 degrees windowed cylindrical light distributor was performed in 19 sheep 4 days after injection of 0.15 mg/kg of tetra(m-hydroxyphenyl) chlorin. Light doses ranged from 10 to 500 J/cm(2) at 514 nm (argon ion laser) and from 5 to 250 J/cm(2) at 413 nm (krypton laser).

RESULTS

Follow-up endoscopies revealed a tissue response with a fibrinous area at almost all light doses, whereas application of extremely high light doses tended to induce circumferential necrosis with subsequent stenosis. Three months after irradiation with green light, histologic examination of the resected specimens revealed transmural scarring at doses higher than 100 J/cm(2). After illumination with blue light, partial or more extensive fibrosis of the muscular layer was observed only at light doses of 175 to 250 J/cm(2).

CONCLUSIONS

Application of high doses of green light after sensitization with tetra(m-hydroxyphenyl) chlorin led to severe complications in the esophagus of the sheep that are highly likely to occur in humans as well. Blue light causes significantly less damage than green light and may, therefore, be considered as an alternative for photodynamic therapy of early stage superficial esophageal cancer.

Uptake and localisation of mTHPC (Foscan) and its 14C-labelled form in normal and tumour tissues of the hamster squamous cell carcinoma model: a comparative study

The aim of this study was to evaluate the pharmacokinetics of meta(tetrahydroxyphenyl)chlorin (mTHPC) on different tissues of interest in a hamster tumour model and to confirm our earlier animal studies on semi-quantitative fluorescence microscopy. The results obtained by three different evaluation methods were compared: in vivo spectrofluorometry, ex vivo fluorescence microscopy and chemical extraction of (14)C-labelled mTHPC. Following intracardiac injection of 0.5 mg kg(-1) mTHPC, groups of five tumour-bearing animals were used for in situ light-induced fluorescence spectroscopy. Afterwards, the biopsies were taken and snap frozen for fluorescence microscopy. The presence of radioactivity in serum and tissues was determined after chemical digestion in scintillation fluid using a scintillation counter. For each analysed tissue, a good correlation was observed between the three evaluation methods. The highest fluorescence intensity and quantities of mTHPC were observed between 12 and 24 h in liver, kidney, serum, vascular endothelium and advanced neoplasia. The majority of mTHPC was found at around 48 h in smooth muscle and at 96 h in healthy cheek pouch mucosa and early malignant lesions. The lowest level of mTHPC was noted in striated muscle at all times. No selectivity in dye localisation was observed between early squamous cell carcinoma and healthy mucosa. Soon after the injection, a significant selectivity was noted for advanced squamous cell carcinoma as compared to healthy cheek pouch mucosa or striated muscle. A significant difference in mTHPC localisation and quantity was also observed between striated and smooth muscle during the first 48 h following the injection. Finally, this study demonstrated the usefulness of non-invasive in situ spectroscopic measurements to be performed systematically prior to photodynamic therapy as a real-time monitoring for each treated patient in order to individualise and adapt the light dosimetry and avoid over or under treatments.

Ablation of Barrett's epithelium: the promise and the problems

The incidence of adenocarcinoma of the esophagus has increased dramatically over recent years. Because Barrett's epithelium is recognized as a risk factor for adenocarcinoma there is an interest in reversing this metaplasia. A number of endoscopic methods of destruction of esophageal columnar epithelium have been described. The purpose of this article is to review the currently available methods of managing Barrett's epithelium with particular reference to the role of ablative therapy in reducing the risk of adenocarcinoma.

In vitro investigation on the pH dependence of the absorption and fluorescence properties of the photosensitizer mTHPC

Fluorescence excitation efficiency is of great importance for photodynamic diagnosis. Because usually a difference in the interstitial pH between normal and tumor tissue occurs, it is necessary to assess the impact of pH on the fluorescence emission intensity of the photosensitizer meta-tetrahydroxyphenylchlorin (mTHPC) in this context. The results obtained by in vitro fluorescence measurements clearly indicate that pH values below 6 lead to a significant decrease in the fluorescence intensity. In the physiological range of pH 6.5-7.2, however, no pH dependence was found. Besides the decrease in the fluorescence intensity of mTHPC for pH < 6, changes in the spectral shape of the absorption were found. These changes can be utilized for "dual-wavelength ratio imaging," using mTHPC as a pH-sensitive indicator with the excitation pair 405 nm/436 nm in the range of pH 3.5-6.

Photodynamic effects of mTHPC on human colon adenocarcinoma cells: photocytotoxicity, subcellular localization and apoptosis

The photodynamic properties of meta-tetra(hydroxyphenyl)chlorin (mTHPC), a promising second-generation photosensitizer, were investigated using a human colon adenocarcinoma cell line (Colo 201 cells). The study on photocytotoxicity using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide reduction assay showed that mTHPC was an effective photosensitizer on Colo 201 cells. The photocytotoxicity of mTHPC showed both drug and light dose-dependent characteristics. To reach LD50, namely, the dose at which 50% of the cells were killed, only 0.45+/-0.15 microg/mL of mTHPC and 3 J/cm2 of light dose were required. The presence of 10% fetal calf serum in culture medium significantly decreased the incorporation of mTHPC into cells and resulted in the reduction of photodynamic efficacy. Using confocal laser scanning microscopy, mTHPC was first shown to localize in lysosomes rather than in mitochondria. Furthermore, nuclear stainings demonstrated that photodynamic therapy with mTHPC induced apoptosis in Colo 201 cells.

Intraoperative photodynamic therapy after pleuropneumonectomy in patients with malignant pleural mesothelioma: dose finding and toxicity results

OBJECTIVE

To determine the optimal administered dose of meta-tetrahydroxyphenylchlorin (mTHPC) for intraoperative photodynamic therapy (IPDT) in resected malignant pleural mesothelioma (MPM). The primary objective of this combination treatment was to improve local tumor control.

DESIGN

Phase I/II dose escalation study.

SETTING

Two Dutch cancer centers.

PATIENTS

The study included 28 patients (2 women, 26 men), with pathologically confirmed MPM. The mean age was 57 years (age range, 37 to 68 years), and the World Health Organization performance score was 0 to 1. Epithelial mesotheliomas were found in 17 patients, a sarcomatous mesothelioma was found in 1 patient, and mixed epithelial sarcomatous mesotheliomas were found in 10 patients.

METHODS

Patients were injected with 0.075 mg/kg (4 patients), 0.10 mg/kg (19 patients), or 0.15 mg/kg (5 patients) mTHPC 4 or 6 days before undergoing surgery and IPDT. Complete surgical resection (i.e., pleuropneumonectomy) was followed by integral illumination with monochromatic light of 652 nm (10 J/cm(2)). The real-time fluence rate measurements were performed using four isotropic detectors in the chest cavity to calculate the total light dose.

RESULTS

Dose-limiting toxicity was reached at the level of 0.15 mg/kg mTHPC. Three patients died in the perioperative period, and one death was directly related to photodynamic therapy. Real-time dosimetry identified 12 patients in whom additional illumination had to be given to the diaphragmatic sinuses, which were unavoidably shielded during integral illumination. In two patients, illumination was cancelled due to the insufficient resectability of the tumor. The median survival time for all 28 patients was 10 months. Local tumor control, 9 months after treatment, was achieved in 13 of the 26 patients treated with IPDT.

CONCLUSION

IPDT using mTHPC, combined with a pleuropneumonectomy, resulted in local control of disease in 50% of the treated cases. The considerable toxicity associated with the procedure, however, precludes its recommendation for widespread use. Stricter patient selection and improvements of the IPDT technique may reduce the toxicity.

mTHPC-mediated photodynamic diagnosis of malignant brain tumors

Radical tumor resection is the basis for the prolonged survival of patients suffering from malignant brain tumors such as glioblastoma multiforme. We have carried out a phase-II study involving 22 patients with malignant brain tumors to assess the feasibility and the effectiveness of the combination of intraoperative photodynamic diagnosis and fluorescence-guided resection (FGR) mediated by the second-generation photosensitizer meta-tetrahydroxyphenylchlorin (mTHPC). In addition, intraoperative photodynamic therapy (PDT) was performed. Several commercially available fluorescence diagnostic systems were investigated for their applicability in clinical practice. We have adapted and optimized a diagnostic system that includes a surgical microscope, an excitation light source (filtered to 370-440 nm), a video camera detection system and a spectrometer for clear identification of the mTHPC fluorescence emission at 652 nm. Especially in regions of faint fluorescence, it turned out to be essential to maximize the spectral information by optimizing and matching the spectral properties of all components, such as excitation source, camera and color filters. To sum up, on the basis of 138 tissue samples derived from 22 tumor specimens, we have been able to achieve a sensitivity of 87.9% and a specificity of 95.7%. This study demonstrates that mTHPC-mediated intraoperative FGR followed by PDT is a highly promising concept in improving the radicality of tumor resection combined with a therapeutic approach.

Photodynamic therapy and the alimentary tract

Photodynamic therapy offers the possibility of relatively selective tumour necrosis and normal tissue healing. It has many potential applications but as yet no clear role. Articles, editorials and case reports published primarily in English and listed in Medline/ISI up to April 2000 or identified by a manual search have been reviewed in an attempt to provide a comprehensive overview of the use of photodynamic therapy in the alimentary tract. It is concluded that photodynamic therapy can be an effective treatment for superficial pre-malignant mucosal lesions and early cancers, especially in diffuse disease. Suitable patients include those wishing to avoid surgery, high risk subjects or those in whom other forms of treatment have failed. Superiority over other methods of ablation has not so far been demonstrated. Cheaper and more effective photosensitizers and improved techniques of light delivery are likely to increase the application of photodynamic therapy.