Photodynamic therapy using 5-aminolaevulinic acid for oesophageal adenocarcinoma associated with Barrett's metaplasia

Inflammatory cell death induced by 5-aminolevulinic acid-photodynamic therapy initiates anticancer immunity

Background

Inflammatory cell death is a form of programmed cell death (PCD) that induces inflammatory mediators during the process. The production of inflammatory mediators during cell death is beneficial in standard cancer therapies as it can break the immune silence in cancers and induce anticancer immunity. Photodynamic therapy (PDT) is a cancer therapy with photosensitizer molecules and light sources to destroy cancer cells, which is currently used for treating different types of cancers in clinical settings. In this study, we investigated if PDT using 5-aminolevulinic (5-ALA-PDT) causes inflammatory cell death and, subsequently, increases the immunogenicity of cancer cells.

Methods

Mouse breast cancer (4T1) and human colon cancer (DLD-1) cells were treated with 5-ALA for 4 hours and then irradiated with a light source. PCD induction was measured by western blot analysis and FACS. Morphological changes were determined by transmission electron microscopy (TEM). BALB/c mice were injected with cell-free media, supernatant of freeze/thaw cells or supernatant of PDT cells intramuscular every week for 4 weeks and then challenged with 4T1 cells at the right hind flank of BALB/c. Tumor growth was monitored for 12 days.

Results

We found that 5-ALA-PDT induces inflammatory cell death, but not apoptosis, in 4T1 cells and DLD-1 cells in vitro. Moreover, when mice were pretreated with 5-ALA-PDT culture supernatant, the growth of 4T1 tumors was significantly suppressed compared to those pretreated with freeze and thaw (F/T) 4T1 culture supernatant.

Conclusion

These results indicate that 5-ALA-PDT induces inflammatory cell death which promotes anticancer immunity in vivo.

Advancements in photodynamic therapy of esophageal cancer

The poor prognosis of patients with esophageal cancer leads to the constant search for new ways of treatment of this disease. One of the methods used in high-grade dysplasia, superficial invasive carcinoma, and sometimes palliative care is photodynamic therapy (PDT). This method has come a long way from the first experimental studies to registration in the treatment of esophageal cancer and is constantly being improved and refined. This review describes esophageal cancer, current treatment methods, the introduction to PDT, the photosensitizers (PSs) used in esophageal carcinoma PDT, PDT in squamous cell carcinoma (SCC) of the esophagus, and PDT in invasive adenocarcinoma of the esophagus. For this review, research and review articles from PubMed and Web of Science databases were used. The keywords used were "photodynamic therapy in esophageal cancer" in the years 2000-2020. The total number of papers returned was 1,000. After the review was divided into topic blocks and the searched publications were analyzed, 117 articles were selected.

Photodynamic therapy in dermatology: Dundee clinical and research experience

Topical photodynamic therapy (PDT) is increasingly accepted and used as a highly effective treatment for superficial non-melanoma skin cancer and dysplasia. We describe the developments in topical PDT for the treatment of skin diseases in our own PDT Centre in Dundee, both clinically and from a research base. Improvements in PDT could be achieved by optimisation of photosensitiser and light delivery, and these goals underpin the aims of our centre. We hope to facilitate the dissemination of use of PDT in dermatology throughout Scotland and outline some of the progress in these areas.

A phase I trial of aminolevulinic acid-photodynamic therapy for treatment of oral leukoplakia

BACKGROUND

Photodynamic therapy with aminolevulinic acid (ALA PDT) for oral leukoplakia has shown promising effects in regression of oral leukoplakia. Although ALA has been extensively studied and is an ideal photosensitizer, the optimal light dose for treatment of oral leukoplakia has not been determined. We conducted a phase I study to determine MTD and DLT of PDT in patients treated with ALA for leukoplakia.

METHODS

Patients with histologically confirmed oral leukoplakia received a single treatment of ALA PDT in cohorts with escalating doses of light (585nm). Clinical, histologic, and biologic markers were assessed.

RESULTS

Analysis of 11 participants is reported. No significant toxicity from ALA PDT was observed in patients who received ALA with a light dose of up to 4J/cm(2). One participant experienced transient grade 3 transaminase elevation due to ALA. One participant had a partial clinical response 3months after treatment. Biologic mucosal risk markers showed no significant associations. Determination of MTD could not be accomplished within a feasible timeframe for completion of the study.

CONCLUSIONS

ALA PDT could be safely administered with a light dose up to 4J/cm(2) and demonstrated activity. Larger studies are needed to fully elucidate the MTD and efficacy of ALA-PDT.

[Accumulation of porphyrins in cells of system of blood induced by 5-aminolaevulinic acid]

The levels and rates of accumulation of porphyrins in lymphoid cells and bone marrow cells treated with exogenous 5-aminolaevulinic acid (ALA) were studied. The dependence of the quantity of porphyrins accumulated in cell on ALA concentrations in the medium had maximum at 0.7-1.0 mM ALA for all the cell types studied (splenocytes, thymocytes, peripheral blood lymphocytes and bone marrow cells). The rate of accumulation of uro-, copro- and protoporphyrins depended on cell types. The lowest and the highest levels were found in splenocytes and highest in bone marrow cells respectively. It is suggested that photodynamic therapy employing ALA is potentially dangerous for blood cells.

Aminolevulinic Acid (ALA) as a Prodrug in Photodynamic Therapy of Cancer

Aminolevulinic acid (ALA) is an endogenous metabolite normally formed in the mitochondria from succinyl-CoA and glycine. Conjugation of eight ALA molecules yields protoporphyrin IX (PpIX) and finally leads to formation of heme. Conversion of PpIX to its downstream substrates requires the activity of a rate-limiting enzyme ferrochelatase. When ALA is administered externally the abundantly produced PpIX cannot be quickly converted to its final product - heme by ferrochelatase and therefore accumulates within cells. Since PpIX is a potent photosensitizer this metabolic pathway can be exploited in photodynamic therapy (PDT). This is an already approved therapeutic strategy making ALA one of the most successful prodrugs used in cancer treatment.

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.

The role of photodynamic therapy in the esophagus

Photodynamic therapy (PDT) is a drug and device therapy using photosensitizer drugs activated by laser light for mucosal ablation. Porfimer sodium PDT has been used extensively with proven long-term efficacy and durability for the ablation of Barrett esophagus and high-grade dysplasia. and early esophageal adenocarcinoma. However, continued use is hampered by an associated stricture risk and prolonged photosensitivity (4-6 weeks). Promising single-center European studies using other forms of PDT, such as aminolevulinic acid PDT, have not been replicated elsewhere, limiting the widespread use of other forms of PDT. Future use of PDT in esophageal disease depends on the development of improved dosimetry and patient selection to optimize treatment outcomes, while minimizing adverse events and complications.

Barrett's esophagus and the increasing role of endoluminal therapy

Barrett's esophagus, or the presence of specialized intestinal mucosa in the esophagus that has a malignant potential, has experienced a rapid increase in diagnosis and prevalence over the past few decades. Once thought to progress to adenocarcinoma in an orderly sequence of increasing dysplasia, recent data suggest the process can be more random. In combination with targeted surveillance endoscopy, recent improvements in technology have aided endoluminal therapy in becoming a cost-effective adjunct to medication. When used in combination, in particular, these ablative therapies have become suitable, if not preferable, alternatives to surgery in many patients.

Endoscopic therapy of dysplasia and early-stage cancers of the esophagus

Endoscopic treatments have become a viable alternative for some patients with early-stage esophageal neoplasia. Although esophagectomy remains the standard of care for high-grade dysplasia and superficial cancers, surgical morbidity and mortality may deter patients who are medically unfit or reluctant to undergo surgery. Photodynamic therapy (PDT) and endoscopic mucosal resection (EMR) are the best-studied nonsurgical approaches at present. PDT has been reported to eradicate high-grade dysplasia (HGD) and early Barrett's cancers at rates ranging from 75% to 100% and 17% to 100%, respectively, and a recent randomized controlled trial confirmed that PDT may prevent progression of HGD to cancer. Complete remission rates greater than 90% have also been reported with EMR and other mucosa-ablating interventions, although recurrence rates necessitate close endoscopic surveillance and retreatment in some patients. In addition to PDT and EMR, several emerging endoscopic treatment options for superficial esophageal neoplasia may provide attractive alternatives to surgery.

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.

5-Aminolaevulinic acid-induced photodynamic therapy and photodetection in Barrett's esophagus

Barrett's esophagus is a precursor of adenocarcinoma of the esophagus. This cancer has the fastest growing incidence of any solid tumor in the Western world. Surveillance of Barrett's esophagus is routinely undertaken to detect early malignant transformation. However, ablative endoscopic treatments are available and these can obliterate the abnormal epithelium, allowing neosquamous regrowth. Photodynamic therapy using 5-aminolaevulinic acid (ALA) is such a technique. In this non-thermal method of ablation, ALA is metabolized to produce the photosensitizer protoprophyrin IX. This, together with light and oxygen, produces local tissue destruction. Fluorescence detection using ALA has also been used to identify areas of dysplasia and thus enhance positive biopsy yield. The use of ALA in photodynamic therapy and photodetection is reviewed.

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.

In situ light dosimetry during photodynamic therapy of Barrett's esophagus with 5-aminolevulinic acid

BACKGROUND AND OBJECTIVES

Previous studies with PhotoDynamic Therapy (PDT) in bladder and bronchi have shown that due to scattering and reflection, the actually delivered fluence rate on the surface in a hollow organ can be significantly higher than expected. In this pilot study, we investigated the differences between the primary calculated and the actual measured fluence rate during PDT of Barrett's Esophagus (BE) using 23 independent clinical measurements in 15 patients.

STUDY DESIGN/MATERIALS AND METHODS

A KTP-dye module laser at 630 nm was used as light source. Light delivery was performed using a cylindrical light diffuser inserted in the center of an inflatable transparent balloon with a length corresponding to the length of the Barrett's epithelium. The total light output power of the cylindrical diffuser was calibrated using an integrating sphere to deliver a primary fluence rate of 100 mW cm(-2). Two fiber-optic pseudo sphere isotropic detectors were placed on the balloon and were used to measure fluence rate at the surface of the esophageal wall during PDT.

RESULTS AND CONCLUSIONS

The actual fluence rate measured was 1.5-3.9 times higher than the primary fluence rate for 630 nm. In general, the fluence rate amplification factor decreased with increasing redness of the tissue and was less for shorter diffusers. Fluence rate variations in time were observed which coincided with patients coughing, movement, and esophageal spasms. These factors combined with inter patient variability of the fluence rate measured appears to justify the routine application of this technique in PDT of BE.

Photodynamic therapy for esophageal cancer: a useful and realistic option

The use of light therapy for tissue destruction is highly attractive for the endoscopic and minimally invasive therapy of esophageal cancer. Photodynamic therapy (PDT) offers the possibility of palliation of advanced obstructing tumors. However, there are other competing techniques, which can be used to open the esophageal lumen. It has also proved very effective in providing prolonged palliation of patients with advanced irresectable cancer. Completely obstructing tumors, tortuous and long lesions, and tumors near the upper end of the esophagus are particularly suitable for photodynamic therapy. Patients with obstruction to an esophageal prosthesis are also well palliated with PDT. A more interesting and exciting development is its use for the eradication of early asymptomatic mucosal disease. Photodynamic therapy is particularly useful for the eradication of field cancerous change in patients with pre-malignant Barrett's esophagus, or early tumors in patients unfit for radical therapy.

Photodynamic therapy for Barrett's esophagus: a review

Barrett's esophagus is the major risk factor for the development of esophageal adenocarcinoma, which is increasing in incidence faster than any other cancer in the Western world. Barrett's esophagus has previously been considered an irreversible lesion that required life-long surveillance to detect malignant transformation. However, endoscopic ablative techniques to destroy the abnormal mucosa and allow squamous regeneration have now been developed. Photodynamic therapy (PDT) is a non-thermal technique where the interaction of a photosensitizer in the tissues and light of a known wavelength results in tissue destruction. It appears to be an effective tool for ablating dysplasia and superficial cancers in Barrett's esophagus. The status of PDT for this disease is reviewed.

Online electrochemical monitoring of nitric oxide during photodynamic therapy

Photodynamic therapy (PDT), as a novel treatment modality, is based on the use of a photosensitizing agent with an excitation light source for the treatment of various malignancies. Its effect is mediated through reactive oxygen species and nitric oxide (NO), which are shown to be present in apoptosis. Individual differences among patients and even in different areas of the same tumor in one patient may cause a major problem with PDT: dose calculation during application of the light. An electrochemical sensor is proposed for online monitoring of NO generation as a solution of this problem. 5-Aminolevulinic acid (ALA) was administered as the photosensitizer in rat cerebellum. An amperometric sensor, selective to NO, was designed and tested both in vitro and in vivo during PDT. ALA-mediated PDT resulted in rapid generation of NO, starting as early as the application of light on the tissue. Simultaneous amperometric recordings have been carried out for 5 min during PDT. The progressive increase in NO concentration peaked at 1.10 min and then the response current began to decrease until it reached a plateau at around 70% of its peak value. This study, for the first time, electrochemically demonstrates the generation of NO during PDT. Rapid and stable responses obtained by the experimental setup confirmed that this method could be used as an online monitoring system for PDT-mediated apoptosis.

Photodynamic therapy for dysplastic Barrett esophagus and early esophageal adenocarcinoma

OBJECTIVE

To evaluate our results using photodynamic therapy (PDT) for the treatment of dysplasia or superficial cancer (T1 N0 M0) in patients with Barrett esophagus.

PATIENTS AND METHODS

We retrospectively reviewed our clinical experience with 48 patients (34 patients with high-grade dysplasia and 14 patients with superficial cancer in Barrett esophagus) who had been referred for PDT. Initial evaluation included computed tomography and standard and high-frequency catheter endosonography. Follow-up endoscopy was performed 4 to 6 weeks after PDT with ablation of any residual glandular mucosa, using the argon plasma coagulator. Patients were then followed up indefinitely every 3 to 6 months with computed tomography, endosonography, and endoscopic surveillance.

RESULTS

The median series follow-up was 18.5 months (range, 1-56 months). Apparent complete photoablation of Barrett mucosa and/or superficial neoplasm was documented in 47 of 48 cases. Complications included symptomatic strictures (11 patients), photosensitivity (7 patients), atrial fibrillation (1 patient) or recurrent congestive heart failure (1 patient), and self-limited esophageal perforation (1 patient). Failure to ablate T1 N0 M0 adenocarcinoma occurred in 1 patient.

CONCLUSIONS

Porfimer sodium PDT appears to eradicate dysplastic Barrett mucosa and neoplasia. These results are promising; however, long-term studies are needed to document the efficacy of PDT in reducing the morbidity and mortality in such patients.

Comparison of 5-aminolaevulinic acid and porphyrin photosensitization for photodynamic therapy of malignant bronchial stenosis: a clinical pilot study

BACKGROUND AND OBJECTIVES

Photosan, a mixture of porphyrin oligomers as sensitizer for photodynamic therapy (PDT), carry the risk of prolonged photosensitivity of the skin. New sensitizer such as 5-aminolaevulinic acid (ALA) with low rates of skin phototoxicity appear to be promising alternatives. The aim of this study was to evaluate the efficacy of ALA compared to Photosan for PDT in malignant tracheo-bronchial stenosis. Reduction of tumor stenosis, increase in quality of life, and phototoxicity were considered as primary objectives. Improvement in clinical symptoms due to reduction of tumor stenosis, for example hemotysis, dyspnea, and poststenotic pneumonia were considered as secondary objectives.

PATIENTS AND METHODS

After diagnostic work-up, photosensitization was done in 16 patients with ALA (60 mg/kg BW, oral, 6-8 hours prior to PDT) and in 24 patients with Photosan (2 mg/kg BW, i.v., 48 hours before PDT). The light dose was calculated as 100 J/cm(2) tumor length. Light at 630 nm was applied using a pumped dye laser. In both groups, additional hyperbaric oxygenation was applied at a level of 2 absolute atmospheric pressure.

RESULTS

Stenosis diameter and Karnofsky performance status showed a significant improvement in favor of the Photosan-group, P = 0.00073 and 0.00015, respectively. In both groups no sunburn occurred due to phototoxicity of the sensitizer.

CONCLUSION

Despite the limitations of a non-randomized study, photosensitization with Photosan seems to be more effective in PDT of malignant tracheo-bronchial stenosis compared to ALA.

The use of 5-aminolaevulinic acid as a photosensitiser in photodynamic therapy and photodiagnosis

Photodynamic therapy (PDT) is a treatment for cancer and pre-malignant conditions, which involves the administration of a photosensitising agent followed by exposure of the tissue to light. 5-Aminolaevulinic acid (ALA) is a naturally occurring compound in the haem biosynthetic pathway, which is metabolised to a photosensitive product, protoporphyrin IX (PpIX). The major advantage of ALA when compared to synthetic photosensitisers is the rapid metabolism, which significantly reduces the period of cutaneous photosensitivity. This review focuses on the development of ALA as a photosensitiser in photodynamic therapy and photodiagnosis, and the wide range of clinical applications in which ALA is now being used as a therapeutic modality.

Does new photosensitizer improve photodynamic therapy in advanced esophageal carcinoma?

BACKGROUND AND OBJECTIVE

Polyhematoporphyrin (Photosan) as sensitizers for photodynamic therapy (PDT) in advanced esophageal cancer carry the risk of prolonged photosensitivity of the skin. New sensitizers such as 5-aminolaevulinic acid (ALA) with low rates of skin phototoxicity appear to be promising alternatives. The aim of this study was to evaluate the efficacy of ALA compared to Photosan for PDT in advanced esophageal carcinoma regarding phototoxicity of the skin, reduction of dysphagia, tumor stenosis, and tumor length and Karnovsky performance status.

STUDY DESIGN/MATERIALS AND METHODS

After diagnostic work-up, photosensitization was done in 22 patients with ALA (60 mg/kg body weight, oral, 6-8 hours prior to PDT) and in 27 patients with Photosan (2 mg/kg body weight, i.v., 48 hours before PDT). The light dose was calculated as 300 J/cm fibre tip. Light at 630 nm was applied using a pumped dye laser. In both groups, additional hyperbaric oxygenation was applied at a level of 2 absolute atmospheric pressure.

RESULTS

Improvement regarding dysphagia, stenosis diameter, and tumor length could be obtained in both treatment arms with a significant difference in favour of the Photosan-group, P = 0.02; P = 0.0000; and P = 0.000014, respectively. The Karnovsky performance status also improved in both groups and showed no significant difference (P = 0.12). The median survival time for the ALA-group was 8.0 months, compared with 9.0 months for the Photosan group. No sunburn or other major treatment related complication occurred in both treatment arms. Thirty-day mortality was 0%.

CONCLUSION

Despite the limitations of a non-randomized study, photosensitzation with Photosan seems to be more effective in PDT of advanced esophageal carcinoma compared to ALA.

Photosensitization with hematoporphyrin derivative compared to 5-aminolaevulinic acid for photodynamic therapy of esophageal carcinoma

BACKGROUND

Hematoporphyrin derivatives (HpD) as sensitizers for photodynamic therapy (PDT) in advanced esophageal cancer carry the risk of prolonged photosensitivity of the skin. New sensitizers such as 5-aminolaevulinic acid (ALA) with low rates of skin phototoxicity appear to be promising alternatives. The aim of this study was to evaluate the efficacy of ALA compared with HpD for PDT in advanced esophageal carcinoma regarding phototoxicity of the skin, reduction of dysphagia, tumor stenosis and length, and Karnovsky performance status.

METHODS

After diagnostic workup, photosensitization was done in 22 patients with ALA (60 mg/kg body weight, oral, 6 to 8 hours before PDT) and in 27 patients with a hematoporphyrin derivative (2 mg/kg body weight, intravenously, 48 hours before PDT). The light dose was calculated as 300 J/cm fiber tip. Light at 630 nm was applied using a pumped dye laser. In both groups, additional hyperbaric oxygenation was applied at a level of 2 absolute atmospheric pressure.

RESULTS

Improvement regarding dysphagia, stenosis diameter, and tumor length could be obtained in both treatment arms with a significant difference in favor of the HpD group (p = 0.02; p = 0.0000; and p = 0.000014, respectively). A questionnaire of patients in the HpD group confirmed that the ability of swallowing a meal was superior compared with the discomfort from limitation to sun exposure. No sunburn or other major treatment-related complication occurred in both treatment arms.

CONCLUSIONS

Despite the limitations of a nonrandomized study, photosensitzation with HpD seems to be more effective in PDT of advanced esophageal carcinoma compared with ALA.

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.

Aminolevulinic acid: pharmacological profile and clinical indication

The role of aminolevulinic acid hydrochloride (ALA) in photodynamic therapy (PDT) of in situ neoplasias and tumours of epithelial tumours is steadily increasing and it has been shown to be the drug with most clinical use in PDT. In dermatology, topical PDT with ALA is already postulated to be the treatment of choice for actinic keratoses and superficial basal cell carcinomas. In gastroenterology, pulmonology, uro- and nephrology, neurology and gynaecology ALA has an important role as a photosensitiser not only in the diagnosis of neoplastic tissue but as therapy; first experiences have been made with PDT in these organs. Besides the therapeutic efficacy of this technique, the fluorescence of ALA-induced porphyrins can be effectively used to detect and delineate epithelial and endothelial neoplasms. In dermatology, other indications for ALA-treatment are non-tumoural applications, especially psoriasis, viral-induced diseases, or acne vulgaris. ALA is an effective compound in the diagnosis or therapy of various epithelial and endothelial neoplastic lesions.

Migraine and beyond: cardiovascular therapeutic potential for CGRP modulators

CGRP is a potent vasodilator that has been shown to have a physiological and/or pathological role in neurogenic inflammation, headaches including migraine, thermal injury, circulatory shock, pregnancy and menopause, hypertension and heart failure and is known to be cardioprotective. CGRP is also a positive inotrope and increases heart rate. Clinical trials have shown beneficial effects of the vasodilatory action of CGRP in hypertension, angina, heart failure, Raynaud's disease and venous stasis ulcers. However, the clinical potential of CGRP is limited as it has to be given by infusion and is quickly broken down. Oral long acting CGRP-mimetics may have potential in disorders in which CGRP has been shown to be beneficial. CGRP-mimetics include capsaicin/vanilloid receptor agonists and gene transfer of an adenoviral vector that encodes prepro-CGRP. CGRP inhibitors have therapeutic potential in conditions in which excessive CGRP-mediated vasodilatation is present; neurogenic inflammation, migraine and other headaches, thermal injury, circulatory shock and flushing in menopause. CGRP inhibitors include capsaicin, antagonists at capsaicin/vanilloid receptors, civamide, CGRP receptor antagonists and 5-HT1D-receptor agonists. Drugs that are 5-HT1D-receptor agonists, the 'triptans' are already commonly used in migraine and the first small molecule CGRP antagonist, BIBN4096BS, is under clinical investigation for the treatment of migraine.

Review article: the potential role for photodynamic therapy in the management of upper gastrointestinal disease

Photodynamic therapy involves the activation of an exogenously administered, or an endogenously generated, photosensitizer with light to produce localized tissue destruction. It is an attractive, predominantly endoscopic technique for the palliation of advanced upper gastrointestinal cancer and the eradication of early neoplastic and pre-neoplastic lesions. The nature of the biological response allowing safe healing and the exploitation of tissue threshold effects mean that adjacent tissue damage can be minimized. This review used a database of 368 papers. The nature of the photosensitizer is critical to the depth of tissue damage and the risk of adjacent tissue damage and stricture formation. The generation of protoporphyrin IX following administration of 5-aminolaevulinic acid has proved useful for the treatment of high-grade dysplasia in Barrett's oesophagus. A double-blind randomized placebo controlled trial has confirmed that it is a safe and effective method for the ablation of low-grade dysplasia. The treatment of more advanced lesions requires exogenously administered photo-sensitizers. However, recent data indicate that the neoplastic potential remains in some patients and continued follow-up is necessary. Photodynamic therapy can be used to eradicate early neoplasia and palliate advanced cancer, but caution is required before a definitive cure can be claimed.