Photodynamic therapy with m-tetrahydroxyphenyl chlorin for high-grade dysplasia and early cancer in Barrett's columnar lined esophagus

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.

Targeted Photodynamic Diagnosis and Therapy for Esophageal Cancer: Potential Role of Functionalized Nanomedicine

Esophageal cancer is often diagnosed at the late stage when cancer has already spread and is characterized by a poor prognosis. Therefore, early diagnosis is vital for a better and efficient treatment outcome. Upper endoscopy with biopsy is the standard diagnostic tool for esophageal cancer but is challenging to diagnose at its premalignant stage, while conventional treatments such as surgery, chemotherapy, and irradiation therapy, are challenging to eliminate the tumor. Photodynamic diagnosis (PDD) and therapy (PDT) modalities that employ photosensitizers (PSs) are emerging diagnostic and therapeutic strategies for esophageal cancer. However, some flaws associated with the classic PSs have limited their clinical applications. Functionalized nanomedicine has emerged as a potential drug delivery system to enhance PS drug biodistribution and cellular internalization. The conjugation of PSs with functionalized nanomedicine enables increased localization within esophageal cancer cells due to improved solubility and stability in blood circulation. This review highlights PS drugs used for PDD and PDT for esophageal cancer. In addition, it focuses on the various functionalized nanomedicine explored for esophageal cancer and their role in targeted PDD and PDT for diagnosis and treatment.

Long-term outcomes of the randomized controlled trial comparing 5-aminolaevulinic acid and Photofrin photodynamic therapy for Barrett's oesophagus related neoplasia

OBJECTIVE

Photodynamic therapy (PDT) was used as therapy for early neoplasia associated with Barrett's oesophagus (BE). This is 5-year follow-up of patients enrolled into randomised controlled trial of 5-aminolaevulinic acid (ALA) vs. Photofrin PDT.

METHODS

Biopsies were taken from original Barrett's segment during endoscopic follow up using Seattle protocol. Endoscopic mucosal resection (EMR) ± radiofrequency ablation (RFA) was preferred therapy in patients who failed PDT and/or had recurrent neoplasia.

RESULTS

Fifty eight of 64 patients enrolled in the original trial were followed up including 31 patients treated with ALA PDT (17 patients with ≤6 cm, 14 patients with >6 cm segment of BE) and 27 treated with Photofrin PDT (14 patients with ≤6 cm, 13 patients with >6 cm BE). Initial success was achieved in 65% (20/31) ALA and 48% (13/27) Photofrin patients (p = .289). Thirty five percent patients (7/20) relapsed in ALA group and 54% (7/13) relapsed in Photofrin group (p = .472). At a median follow-up of 67 months, no significant difference was found in long-term complete reversal of intestinal metaplasia (CR-IM) and complete reversal of dysplasia (CR-D) between ALA and Photofrin groups (78% vs. 63%; p = .18; 90% vs. 76%; p = .26). Original length of BE did not alter long-term outcome. Four patients from each group progressed to invasive oesophageal adenocarcinoma. Initial success of ALA PDT was associated with significantly better likelihood of long-term remission (p = .03).

CONCLUSIONS

Initial response to PDT plays key role in long term outcome. RFA ± EMR have, however, become preferred minimally invasive ablative therapy for BE-related neoplasia due to poor efficacy of PDT.

Esophageal neoplasia arising from subsquamous buried glands after an apparently successful photodynamic therapy or radiofrequency ablation for Barrett's associated neoplasia

OBJECTIVE

Photodynamic therapy (PDT) and radiofrequency ablation (RFA) are effective non-surgical options for the treatment of Barrett's esophagus (BE) associated neoplasia. Development of subsquamous intestinal metaplasia after successful PDT and/or RFA is a recognized phenomenon; however, the occurrence of neoplasia arising from buried glands is a rare complication.

METHODS

This is a prospective case series of patients treated with PDT and/or RFA from 1999 to 2014 at University College London Hospital for neoplasia associated with BE, whose outcomes were analyzed retrospectively. Prior to any ablative therapy any visible nodularity was removed with endoscopic mucosal resection (EMR). After successful PDT and/or HALO RFA treatment, defined as a complete reversal of dysplasia and metaplasia, patients underwent endoscopic follow up using the Seattle protocol.

RESULTS

A total of 288 patients were treated, 91 with PDT between 1999 and 2010, 173 with RFA between 2007 and 2014, and 24 with both PDT and RFA for neoplasia associated with BE. Subsquamous neoplasia occurred in seven patients (7/288, 2%). The first patient developed subsquamous invasive adenocarcinoma and underwent curative surgery. Another five patients with subsquamous neoplasia (either high-grade dysplasia or intramucosal cancer) were treated successfully with EMR. The final patient developed subsquamous invasive esophagogastric junctional adenocarcinoma with liver metastases.

CONCLUSION

Development of subsquamous neoplasia after an apparently successful PDT and/or RFA is a rare but recognized complication. Clinicians should be aware of this phenomenon and have a low threshold for performing an EMR. Thorough surveillance following successful PDT and/or RFA ensuring high-quality endoscopy is required.

Endoscopic Therapy of Neoplasia Related to Barrett's Esophagus and Endoscopic Palliation of Esophageal Cancer

Background

Barrett's esophagus (BE) is the most important identifiable risk factor for the progression to esophageal adenocarcinoma.

Methods

This article reviews the current endoscopic therapies for BE with high-grade dysplasia and intramucosal cancer and briefly discusses the endoscopic palliation of advanced esophageal cancer.

Results

The diagnosis of low-grade or high-grade dysplasia (HGD) is based on several cytologic criteria that suggest neoplastic transformation of the columnar epithelium. HGD and carcinoma in situ are regarded as equivalent. The presence of dysplasia, particularly HGD, is also a risk factor for synchronous and metachronous adenocarcinoma. Dysplasia is a marker of adenocarcinoma and also has been shown to be the preinvasive lesion. Esophagectomy has been the conventional treatment for T1 esophageal cancer and, although debated, is an appropriate option in some patients with HGD due to the presence of occult cancer in over one-third of patients.

Conclusions

Endoscopic ablative modalities (eg, photodynamic therapy and cryoablation) and endoscopic resection techniques (eg, endoscopic mucosal resection) have demonstrated promising results. The significant morbidity and mortality of esophagectomy makes endoscopic treatment an attractive potential option.

Prevalence of adenocarcinoma at esophagectomy for Barrett's esophagus with high grade dysplasia

BACKGROUND

Barrett's esophagus with high grade dysplasia (HGD) may require surgical resection because of the risk of concomitant adenocarcinoma. The prevalence of invasive, occult carcinoma (≥stage 1B) in this setting has varied. We investigated the association of adenocarcinoma at operative resection for high grade dysplasia.

METHODS

Using an electronic medical record, we identified patients who underwent esophagectomy for high grade dysplasia at the University of Pittsburgh Medical Center between 1993 and 2007. Preoperative diagnosis was confirmed by reviewing endoscopic, radiologic and pathology reports. Postoperative pathology reports were compared to the preoperative diagnosis.

RESULTS

68 patients (12 females and 56 males) with a preoperative diagnosis of high grade dysplasia underwent operative resection. The mean age was 64 years (range 36 to 86 years). Of 68 patients, 12 (17.6%) had adenocarcinoma, 2 (2.9%) were downgraded to low grade dysplasia, and 54 (79.4%) were confirmed as HGD. Of the 12 patients with adenocarcinoma, 4 (5.9% of total cohort) had intramucosal cancer (Stage 1A) and 8 (11.7% of total cohort) had invasive cancer with submucosal invasion or more advanced disease. Of the 8 patients with invasive adenocarcinoma, 4 did not have preoperative endoscopic or radiologic testing suggestive of advanced disease.

CONCLUSION

The overall prevalence of adenocarcinoma in association with a preoperative diagnosis of HGD was 17.6%. Invasive adenocarcinoma was present in 11.7% of subjects and was clinically occult in 5.9%.

Photodynamic therapy with systemic meta-tetrahydroxyphenylchlorin in the treatment of anal intraepithelial neoplasia, grade 3

BACKGROUND AND OBJECTIVE

Anal cancer and preneoplastic anal lesions (anal intraepithelial neoplasia, AIN) rising especially in men having sex with men (MSM). There are no widely accepted treatment standards for AIN. Photodynamic therapy (PDT) using the systemic sensitizer meta-tetrahydroxyphenylchlorin (mTHPC) has the potential to treat the anal area even when the exact borders of the preneoplastic anal lesion cannot easily be visualized.

STUDY DESIGN/MATERIALS AND METHODS

In this prospective intervention study, 15 HIV-positive MSM with AIN 3 were treated in 25 PDT-sessions using mTHPC intravenously administered at drug doses of 0.075-0.15 mg ml(-1) and illumination at 48  hours. The illumination was performed using a custom made applicator using either red light (652 nm) to a measured intended fluence of 10 and 20 J cm(-2) and green light (532 nm) to a measured intended fluence of 105, 210, and 340 J cm(-2) . Red and green illuminations were performed at a (green) equivalent fluence rate of 105 mW cm(-2) .

RESULTS

Initial complete response was seen in 7/25 (28%) of treatments and another 4/25 (16%) initial partial responses. After an average 8 months, recurrences were detected in 7/11 (64%) of sessions that initially showed response. A total 4/25 (16%) showed persistent complete response 6-15 months after green light illumination. Red light illuminations caused more significant side effects combined with no persistent complete response. Reported side effects were intense pain, bloody and purulent rectal discharge, and anal stricture formation, in one patient.

CONCLUSION

The results show that the use of systemic mTHPC is partially effective for the treatment of AIN 3.

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.

Photodynamic therapy (PDT) using HPPH for the treatment of precancerous lesions associated with Barrett's esophagus

BACKGROUND AND OBJECTIVES

Photodynamic therapy (PDT) with porfimer sodium, FDA approved to treat premalignant lesions in Barrett's esophagus, causes photosensitivity for 6-8 weeks. HPPH (2-[1-hexyloxyethyl]-2-devinyl pyropheophorbide-a) shows minimal photosensitization of short duration and promising efficacy in preclinical studies. Here we explore toxicity and optimal drug and light dose with endoscopic HPPH-PDT. We also want to know the efficacy of one time treatment with HPPH-PDT.

STUDY DESIGN/MATERIALS AND METHODS

Two nonrandomized dose escalation studies were performed (18 patients each) with biopsy-proven high grade dysplasia or early intramucosal adenocarcinoma of esophagus. HPPH doses ranged from 3 to 6 mg/m2 . At 24 or 48 hours after HPPH administration the lesions received one endoscopic exposure to 150, 175, or 200 J/cm of 665 nm light.

RESULTS

Most patients experienced mild to moderate chest pain requiring symptomatic treatment only. Six patients experienced grade 3 and 4 adverse events (16.6%). Three esophageal strictures were treated with dilatation. No clear pattern of dose dependence of toxicities emerged. In the drug dose ranging study (light dose of 150 J/cm at 48 hours), 3 and 4 mg/m2 of HPPH emerged as most effective. In the light dose ranging study (3 or 4 mg/m2 HPPH, light at 24 hours), complete response rates (disappearance of high grade dysplasia and early carcinoma) of 72% were achieved at 1 year, with all patients treated with 3 mg/m2 HPPH plus 175 J/cm and 4 mg/m2 HPPH plus 150 J/cm showing complete responses at 1 year.

CONCLUSIONS

HPPH-PDT for precancerous lesions in Barrett's esophagus appears to be safe and showing promising efficacy. Further clinical studies are required to establish the use of HPPH-PDT.

[Endoscopic treatments for Barrett oesophagus]

High grade dysplasia and superficial carcinomas (with no extension under muscularis mucosae) can be indications for endoscopic treatments of Barrett oesophagus. When an endoscopic treatment is considered, a gastroscopy with use of acetic acid and planimetry and the confirmation of high-grade dysplasia by a new examination after PPI treatment and a pathologic second confirmation is needed. For high-grade dysplasia in focalised and visible lesions, an endoscopic resection by EMR or ESD should be proposed: it allows a more accurate pathologic examination and can be an effective curative treatment. After endoscopic resection of visible high grade dysplasia lesions, a complete eradication of Barrett oesophagus may be proposed to prevent dysplasia recurrence. In case of extensive high-grade dysplasia or to eradicate Barrett oesophagus residual lesions, radiofrequency ablation is the preferred endoscopic technique. Photodynamic therapy may also be proposed for more invasive lesions or after other endoscopic techniques with mucosal scars. Surgical oesophagus resection is still recommended for diffuse high-grade dysplasia in young patients or in case of pathologic pejorative criteria in endoscopic resection specimen. In case of Low-grade dysplasia, either endoscopic surveillance should be performed every six or 12 months or radiofrequency ablation could be proposed in the yield of prospective studies.

Current state of endoscopic therapies in Barrett's esophagus and esophageal cancer

Barrett's esophagus (BE) is a premalignant condition that predisposes patients to esophageal adenocarcinoma. This risk increases with increasing dysplasia, especially in patients with BE and high-grade dysplasia. Radical esophagectomy had long been the only option for these patients; however, it has been associated with significant morbidity and mortality. Endoscopic therapies have been increasingly used as an alternative to radical esophagectomy given the minimally invasive nature and tolerability of the procedure relative to surgery. Currently, the most widely used endoscopic therapies include endoscopic mucosal resection, photodynamic therapy, CryoSpray ablation, and radiofrequency ablation. Retrospective and prospective studies on the use of each of these modalities in patients with nondysplastic BE, dysplastic BE, and early esophageal cancer have demonstrated their effectiveness in eradication of dysplasia with or without reversion of Barrett's epithelium to normal squamous epithelium of the esophagus. These modalities are well tolerated, safe, and have few side effects. Ultimately, more research is needed regarding their ability to fully displace surgical intervention as the gold standard, although at this point their role in poor operative candidates or patients seeking conservative approaches remains promising.

Endotherapy for Barrett's esophagus: Which, how, when, and who?

Recent developments in endoscopic therapeutic options for Barrett's esophagus (BE) early neoplasia have resulted in a dramatic paradigm shift in its clinical management. With multiple endoscopic choices available, it is important to discern subtle differences between these approaches based on the available current data and known limitations of each modality. The goals of endoscopic therapy of Barrett's neoplasia are to preserve the esophagus while ablating or removing the entire BE segment. This article reviews the currently available BE endoscopic treatments with emphasis on appropriate selection of patients, indications and timing of use, and clinical management considerations.

Photodynamic therapy

Photodynamic therapy (PDT) is a photochemical process that uses a photosensitizer drug activated by laser light to produce mucosal ablation. Porfimer sodium PDT has proved long-term efficacy and durability in the treatment of Barrett's esophagus and high-grade dysplasia and early esophageal adenocarcinoma. Its use has been limited by serious side effects including prolonged cutaneous photosensitivity and stricture formation. Other photosensitizers with a better safety profile have been used mostly in Europe with limited experience. The future of PDT lies on a better understanding of dosimetry, tissue properties, and host genetic factors.

Endoscopic treatments for Barrett's esophagus: a systematic review of safety and effectiveness compared to esophagectomy

BACKGROUND

Recently, several new endoscopic treatments have been used to treat patients with Barrett's esophagus with high grade dysplasia. This systematic review aimed to determine the safety and effectiveness of these treatments compared with esophagectomy.

METHODS

A comprehensive literature search was undertaken to identify studies of endoscopic treatments for Barrett's esophagus or early stage esophageal cancer. Information from the selected studies was extracted by two independent reviewers. Study quality was assessed and information was tabulated to identify trends or patterns. Results were pooled across studies for each outcome. Safety (occurrence of adverse events) and effectiveness (complete eradication of dysplasia) were compared across different treatments.

RESULTS

The 101 studies that met the selection criteria included 8 endoscopic techniques and esophagectomy; only 12 were comparative studies. The quality of evidence was generally low. Methods and outcomes were inconsistently reported. Protocols, outcomes measured, follow-up times and numbers of treatment sessions varied, making it difficult to calculate pooled estimates.The surgical mortality rate was 1.2%, compared to 0.04% in 2831 patients treated endoscopically (1 death). Adverse events were more severe and frequent with esophagectomy, and included anastomotic leaks (9.4%), wound infections (4.1%) and pulmonary complications (4.1%). Four patients (0.1%) treated endoscopically experienced bleeding requiring transfusions. The stricture rate with esophagectomy (5.3%) was lower than with porfimer sodium photodynamic therapy (18.5%), but higher than aminolevulinic acid (ALA) 60 mg/kg PDT (1.4%). Dysphagia and odynophagia varied in frequency across modalities, with the highest rates reported for multipolar electrocoagulation (MPEC). Photosensitivity, an adverse event that occurs only with photodynamic therapy, was experienced by 26.4% of patients who received porfimer sodium.Some radiofrequency ablation (RFA) or argon plasma coagulation (APC) studies (used in multiple sessions) reported rates of almost 100% for complete eradication of dysplasia. But the study methods and findings were not adequately described. The other studies of endoscopic treatments reported similarly high rates of complete eradication.

CONCLUSIONS

Endoscopic treatments offer safe and effective alternatives to esophagectomy for patients with Barrett's esophagus and high grade dysplasia. Unfortunately, shortcomings in the published studies make it impossible to determine the comparative effectiveness of each of the endoscopic treatments.

Endoscopic treatment of Barrett’s esophagus: From metaplasia to intramucosal carcinoma

The annual incidence of adenocarcinoma arising from Barrett’s esophagus (BE) is approximately 0.5%. Through a process of gradual transformation from low-grade dysplasia to high-grade dysplasia (HGD), adenocarcinoma can develop in the setting of BE. The clinical importance of appropriate identification and treatment of BE in its various stages, from intestinal metaplasia to intramucosal carcinoma (IMC) hinges on the dramatically different prognostic status between early neoplasia and more advanced stages. Once a patient has symptoms of adenocarcinoma, there is usually locally advanced disease with an approximate 5-year survival rate of about 20%. Esophagectomy has been the gold standard treatment for BE with HGD, due to the suspected risk of harboring occult invasive carcinoma, which was traditionally estimated to be as high as 40%. In recent years, the paradigm of BE early neoplasia management has recently evolved, and endoscopic therapies (endoscopic mucosal resection, radiofrequency ablation, and cryotherapy) have entered the clinical forefront as acceptable non-surgical alternatives for HGD and IMC. The goal of endoscopic therapy for HGD or IMC is to ablate all BE epithelium (both dysplastic and non-dysplastic) due to risk of synchronous/metachronous lesion development in the remaining BE segment.

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.

The role of photodynamic therapy (PDT) physics

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

Advances in photodynamic therapy for gastrointestinal tumors and its propect

This paper reviews the photodynamic therapy for gastrointestinal tumors and its mechanisms, and describes the authors' experience with it. It is feasible and reasonable to use photodynamic therapy for gastrointestinal tumors. It is not in contradiction with PDT and traditional surgical treatment, chemotherapy, radiation and immune therapy, etc. The main mechanisms of photodynamic therapy for gastrointestinal tumors are to damage tumor microvasculature, induce cancer cell apoptosis, injure cancer cell membrane, and trigger immune reactions.

Detection and treatment of dysplasia in Barrett's esophagus: a pivotal challenge in translating biophotonics from bench to bedside

Barrett's esophagus (BE) is a condition that poses high risk of developing dysplasia leading to cancer. Detection of dysplasia is a critical element in determining therapy but is extremely challenging, so that standard white-light endoscopy is used only as a means to guide biopsy. Many novel optical techniques have been aimed at this problem, including various forms of improved wide-field white-light (chromoendscopy/magnification and narrow-band) and fluorescence imaging, and "optical biopsy" techniques (diffuse reflectance, elastic light scattering, fluorescence and Raman spectroscopies, confocal microendoscopy, and optical coherence tomography). While promising, either as stand-alone modalities or in combination, to date none has solved this pivotal challenge to the point of clinical adoption. Likewise, minimally invasive treatment of BE patients with dysplasia remains suboptimal, despite recent approval of photodynamic therapy for this indication. This work presents a critique and summary of each of these biophotonic technologies, and discusses the fundamental advantages and limitations of each. The future directions for this field are considered, particularly from the perspective of relying on intrinsic (endogenous) optical signatures compared with the use of exogenous contrast agents.

Influence of Incubation Time and Sensitizer Localization on Meta-tetra(hydroxyphenyl)chlorin (mTHPC)-Induced Photoinactivation of Cells

The present study addresses the impact of different aggregation states of meta-tetra(hydroxyphenyl)chlorin (mTHPC) on the photoinactivation of cells. Measurements of the photophysical properties of mTHPC in MCF-7 cells showed progressive sensitizer aggregation with increasing incubation time. Reconstructed absorption spectra of intracellular mTHPC showed a significant decrease in the molar extinction coefficient and broadening of the Soret band at 24 h incubation compared to 3 h. Intracellular photobleaching of mTHPC slowed down, and the profile changed from mono- to bi-exponential upon incubation. Fluorescence lifetime imaging (FLIM) measurements revealed a substantial decrease in the lifetime of mTHPC fluorescence at 24 h compared to 3 h. In addition, the intracellular localization of mTHPC as observed by fluorescence microscopy changed from a diffuse homogeneous fluorescence pattern at short incubation times to a punctiform pattern at 24 h. The efficiency of photodynamic therapy (PDT) assessed by a clonogenic assay was three times greater at 24 h. However, when the survival curves were replotted as a function of the number of absorbed photons, the efficiency was 1.8 times greater at 3 h than at 24 h. The loss of photosensitizing efficiency at higher mTHPC concentrations was attributed to self-quenching of the triplet states of the sensitizers.

How light dosimetry influences the efficacy of photodynamic therapy with 5-aminolaevulinic acid for ablation of high-grade dysplasia in Barrett's esophagus

Photodynamic therapy (PDT) with 5-aminolaevulinic acid (ALA) is a novel treatment for high-grade dysplasia (HGD) in Barrett's esophagus (BE). Our aim was to evaluate the effectiveness of differing light doses. Patients with HGD in BE received oral ALA (60 mg/kg) activated by low (500 J/cm), medium (750 J/cm), high (1,000 J/cm), or highest (1,000 J/cm x2) light dose at 635 nm. Follow-up was by regular endoscopy with quadrantic biopsies. Twenty-four patients were treated. Successful eradication of HGD was significantly correlated with light dose (log rank, p < 0.01). Six of eight patients (75%) treated with the highest light dose, one of two treated with high dose (50%), two of nine (22%) receiving medium light dose, and zero of five receiving low light dose had successful eradication of HGD (median follow-up 45 months, range 1-78 months). No skin photosensitivity or esophageal strictures occurred. The efficacy of ALA-PDT for eradication of HGD in BE is closely related to the light dose used. With a drug dose of 60 mg/kg and light at 635 nm, we recommend a minimum light dose of 1,000 J/cm of esophagus. This dose appears safe.

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.

Relationship between subcellular localisation of Foscan and caspase activation in photosensitised MCF-7 cells

The present study investigates the relationship between the subcellular localisation of Foscan® and intrinsic apoptotic pathway post Foscan®-based photodynamic therapy (PDT). With this purpose, mammary carcinoma MCF-7 cells were incubated with Foscan® for 3 or 24 h and then subjected to equitoxic light doses. Fluorescence microscopy revealed very good Foscan® co-localization to endoplasmic reticulum (ER) and Golgi apparatus after 3 h incubation with MCF-7 cells. Progressive increase in incubation time shows leakage of Foscan® from Golgi apparatus. Twenty-four hours incubation yielded a fluence-dependent enhanced induction of the ER-resident glucose-regulated protein 78 (Bip/GRP78), along with a weak mitochondrial damage, thus underscoring the ER as the main site of photodamage after prolonged incubation. Analysis of events implicated in apoptotic pathway after 24 h incubation demonstrated photodamage to Bcl-2 protein in total cellular extract, but not in the mitochondrial fraction. We further determined an increase in caspases-7 and -6 activation, which was strongly related to the expression of GRP78. The above findings demonstrate that Foscan® localisation in ER improves the photoactivation of the caspase-7 apoptotic pathway, which is poorly related to mitochondrial damage.

Endoluminal therapy for Barrett's esophagus

This article reviews methods to minimize the complications associated with endoscopic therapy for patients with Barrett's esophagus. To place this discussion in context, the natural history of Barrett's esophagus and the risks associated with progression to dysplasia and invasive carcinoma are reviewed. Operative esophageal resection traditionally is recommended for patients with Barrett's high-grade dysplasia and early carcinoma, and these surgical risks also are reviewed. Finally, all currently approved and commercially available methods for endoscopic ablation and resection of Barrett's disease are categorized according to their application methods of ablation: focal ablation, field ablation, and mucosal resection. The clinical experience with these devices is reviewed with their associated adverse events and complications. Caveats, concerns, and recommendations are discussed to help minimize the complications associated with the use of these important technologies that hold the promise of removing or destroying Barrett's disease to prevent the development of invasive carcinoma.