Comparison of high- vs low-dose 5-aminolevulinic acid for photodynamic therapy of Barrett's esophagus

Screening for esophageal adenocarcinoma and precancerous conditions (dysplasia and Barrett's esophagus) in patients with chronic gastroesophageal reflux disease with or without other risk factors: two systematic reviews and one overview of reviews to inform a guideline of the Canadian Task Force on Preventive Health Care (CTFPHC)

BACKGROUND

Two reviews and an overview were produced for the Canadian Task Force on Preventive Health Care guideline on screening for esophageal adenocarcinoma in patients with chronic gastroesophageal reflux disease (GERD) without alarm symptoms. The goal was to systematically review three key questions (KQs): (1) The effectiveness of screening for these conditions; (2) How adults with chronic GERD weigh the benefits and harms of screening, and what factors contribute to their preferences and decision to undergo screening; and (3) Treatment options for Barrett's esophagus (BE), dysplasia or stage 1 EAC (overview of reviews).

METHODS

Bibliographic databases (e.g. Ovid MEDLINE®) were searched for each review in October 2018. We also searched for unpublished literature (e.g. relevant websites). The liberal accelerated approach was used for title and abstract screening. Two reviewers independently screened full-text articles. Data extraction and risk of bias assessments were completed by one reviewer and verified by another reviewer (KQ1 and 2). Quality assessments were completed by two reviewers independently in duplicate (KQ3). Disagreements were resolved through discussion. We used various risk of bias tools suitable for study design. The GRADE framework was used for rating the certainty of the evidence.

RESULTS

Ten studies evaluated the effectiveness of screening. One retrospective study reported no difference in long-term survival (approximately 6 to 12 years) between those who had a prior esophagogastroduodenoscopy and those who had not (adjusted HR 0.93, 95% confidence interval (CI) 0.58-1.50). Though there may be higher odds of a stage 1 diagnosis than a more advanced diagnosis (stage 2-4) if an EGD had been performed in the previous 5 years (OR 2.27, 95% CI 1.00-7.67). Seven studies compared different screening modalities, and showed little difference between modalities. Three studies reported on patients' unwillingness to be screened (e.g. due to anxiety, fear of gagging). Eleven systematic reviews evaluated treatment modalities, providing some evidence of early treatment effect for some outcomes.

CONCLUSIONS

Little evidence exists on the effectiveness of screening and values and preferences to screening. Many treatment modalities have been evaluated, but studies are small. Overall, there is uncertainty in understanding the effectiveness of screening and early treatments.

SYSTEMATIC REVIEW REGISTRATIONS

PROSPERO (CRD42017049993 [KQ1], CRD42017050014 [KQ2], CRD42018084825 [KQ3]).

On the in vivo photochemical rate parameters for PDT reactive oxygen species modeling

Photosensitizer photochemical parameters are crucial data in accurate dosimetry for photodynamic therapy (PDT) based on photochemical modeling. Progress has been made in the last few decades in determining the photochemical properties of commonly used photosensitizers (PS), but mostly in solution or in vitro. Recent developments allow for the estimation of some of these photochemical parameters in vivo. This review will cover the currently available in vivo photochemical properties of photosensitizers as well as the techniques for measuring those parameters. Furthermore, photochemical parameters that are independent of environmental factors or are universal for different photosensitizers will be examined. Most photosensitizers discussed in this review are of the type II (singlet oxygen) photooxidation category, although type I photosensitizers that involve other reactive oxygen species (ROS) will be discussed as well. The compilation of these parameters will be essential for ROS modeling of PDT.

5-Aminolevulinic Acid-Protoporphyrin IX Fluorescence-Guided Surgery of High-Grade Gliomas: A Systematic Review

The current first-line treatment of malignant gliomas consists in surgical resection (if possible) as large as possible. The existing tools don't permit to identify the limits of tumor infiltration, which goes beyond the zone of contrast enhancement on MRI. The fluorescence-guided malignant gliomas surgery was started 15 years ago and had become a standard of care in many countries. The technique is based on fluorescent molecule revelation using the filters, positioned within the surgical microscope. The fluorophore, protoporphyrin IX (PpIX), is converted in tumoral cells from 5-aminolevulinic acid (5-ALA), given orally before surgery. Many studies have shown that the ratio of gross total resections was higher if the fluorescence technique was used. The fluorescence signal intensity is correlated to the cell density and the PpIX concentration. The current method has a very high specificity but still lower sensibility, particularly regarding the zones with poor tumoral infiltration. This book reviews the principles of the technique and the results (extent of resection and survival).

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.

Photodynamic Therapy for Barrett's Esophagus and Esophageal Carcinoma

This paper reviews the use of photodynamic therapy (PDT) in patients with Barrett's esophagus and esophageal carcinoma. We describe the history of PDT, mechanics, photosensitizers for PDT in patients with esophageal disease. Finally, we discuss its utility and limitations in this setting.

Aminolevulinic acid (ALA)-protoporphyrin IX fluorescence guided tumour resection. Part 2: theoretical, biochemical and practical aspects

The importance of the extent of resection for gliomas, and the utility of aminolevulinic acid (ALA) and protoporphyrin IX fluorescence in increasing the extent of resection, has become increasingly evident over the past decade. This review continues from Part 1 and focuses on the biochemical mechanisms by which ALA ingestion leads to tumour fluorescence, and discusses practicalities of the equipment and techniques needed to introduce ALA and fluorescence guided resection into neurosurgical practice.

Buried metaplasia after endoscopic ablation of Barrett's esophagus: a systematic review

OBJECTIVES

Endoscopic ablation of Barrett's esophagus can bury metaplastic glands under a layer of neosquamous epithelium. To explore the frequency and importance of buried metaplasia, we have conducted a systematic review of reports on endoscopic ablation.

METHODS

We performed computerized and manual searches for articles on the results of photodynamic therapy (PDT) and radiofrequency ablation (RFA) for Barrett's esophagus. We extracted information on the number of patients treated, biopsy protocol, biopsy depth, and frequency of buried metaplasia.

RESULTS

We found 9 articles describing 34 patients with neoplasia appearing in buried metaplasia (31 after PDT). We found five articles describing a baseline prevalence of buried metaplasia (before ablation) ranging from 0% to 28%. In 22 reports on PDT for 953 patients, buried metaplasia was found in 135 (14.2%); in 18 reports on RFA for 1,004 patients, buried metaplasia was found in only 9 (0.9%). A major problem limiting the conclusions that can be drawn from these reports is that they do not describe specifically how frequently biopsy specimens contained sufficient subepithelial lamina propria to be informative for buried metaplasia.

CONCLUSIONS

Endoscopic ablation can bury metaplastic glands with neoplastic potential but, even without ablation, buried metaplasia often is found in areas where Barrett's epithelium abuts squamous epithelium. Buried metaplasia is reported less frequently after RFA than after PDT. However, available reports do not provide crucial information on the adequacy of biopsy specimens and, therefore, the frequency and importance of buried metaplasia after endoscopic ablation remain unclear.

The significance of "indefinite for dysplasia" grading in Barrett metaplasia

CONTEXT

For a confident diagnosis of dysplasia in Barrett metaplasia, the epithelial atypia should also involve the surface epithelium. However, pathologists are often faced with biopsies where the crypts show dysplasia, but the surface epithelium is either uninvolved or unevaluable. We previously grouped these cases with indefinite for dysplasia (IND).

OBJECTIVE

To determine the clinical significance of IND grading in Barrett metaplasia.

DESIGN

All biopsies from 276 prospectively followed patients with Barrett metaplasia, who did not have high-grade dysplasia (HGD) or esophageal adenocarcinoma (EAC) on initial biopsy, were graded as negative for dysplasia, IND, low-grade dysplasia (LGD), HGD, and EAC. Biopsies with multifocal IND or LGD were graded as INDM or LGDM, respectively.

RESULTS

Only 3 of 193 patients (2%) with an initial diagnosis of negative for dysplasia and only 1 of 48 patients (2%) diagnosed with IND progressed to HGD or EAC. By contrast, 1 of 7 patients (14%) with INDM, 2 of 21 (10%) with LGD, and 1 of 7 (14%) with LGDM progressed to HGD or EAC. There was no significant difference in progression rate between patients with an initial diagnosis of negative for dysplasia and those diagnosed IND nor were there significant differences among patients with initial diagnoses of INDM, LGD, or LGDM. Kaplan-Meier analysis showed that patients with INDM, LGD, or LGDM on initial biopsy (group 1) were more likely to progress to HGD or EAC than were those patients who were diagnosed negative for dysplasia or IND (group 2; log-rank test, P < .001).

CONCLUSIONS

Multifocal IND in an esophageal biopsy from a patient with Barrett metaplasia has the same clinical implication as LGD.

Photodynamic therapy for Barrett's esophagus: a systematic review

AIM: To evaluate the efficacy and safety of photodynamic therapy (PDT) for Barrett's esophagus (BE).

METHODS: We searched Cochrane Clinical Trial Register (Issue 4, 2009), Medline or PubMed (1978-2010), EMBase (1978-2010), OVID database (1978-2010), Chinese Biological Medicine database (CBMDisc) (1978-2010), CNKI (1979-2010), Chinese VIP database (1989-2010) and Wanfang database (1978-2010). We also manually searched the bibliographies of retrieved articles and four kinds of important journals to identify randomized controlled trials of PDT for BE. A systematic review was conducted using the method recommended by the Cochrane collaboration.

RESULTS: Ten randomized controlled trials involving 731 patients were included in this systematic review. Three trials reported that PDT could provide safe and effective ablation of low-grade dysplastic epithelium, and proposed that PDT could be used for the treatment of BE at 4-5 h after ALA ingestion and low-dose PDT appeared to be a safe protocol for BE. Three trials showed that PDT in combination with omeprazole was an effective therapy for ablating HGD in patients with BE and in reducing the incidence of esophageal adenocarcinoma. Three trials reported that APC and PDT were equally effective in eradicating Barrett's mucosa, with PDT being the more expensive treatment. However, PDT is more effective in eradicating dysplasia. One trial showed that oral prednisone after PDT did not reduce the incidence of esophageal strictures.

CONCLUSION: PDT is an effective therapy for ablating HGD in patients with BE and in reducing the incidence of esophageal adenocarcinoma. Low-dose PDT is better tolerated in patients with BE.

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 relationship of phthalocyanine 4 (pc 4) concentrations measured noninvasively to outcome of pc 4 photodynamic therapy in mice

The ability to noninvasively measure photosensitizer concentration at target tissues will allow optimization of photodynamic therapy (PDT) and could improve outcome. In this study, we evaluated whether preirradiation tumor phthalocyanine 4 (Pc 4) concentrations, measured noninvasively by the optical pharmacokinetic system (OPS), correlated with tumor response to PDT. Mice bearing human breast cancer xenografts were treated with 2 mg kg(-1) Pc 4 iv only, laser irradiation (150 J cm(-2)) only, Pc 4 followed by fractionated irradiation or Pc 4 followed by continuous irradiation. Laser irradiation treatment was initiated when the tumor to skin ratio of Pc 4 concentration reached a maximum of 2.1 at 48 h after administration. Pc 4 concentrations in tumor, as well as in Intralipid in vitro, decreased monoexponentially with laser fluence. Pc 4-PDT resulted in significant tumor regression, and tumor response was similar in the groups receiving either fractionated or continuous irradiation treatment after Pc 4. Tumor growth delay following Pc 4-PDT correlated with OPS-measured tumor Pc 4 concentrations at 24 h prior to PDT (R2=0.86). In excised tumors, OPS-measured Pc 4 concentrations were similar to the HPLC-measured concentrations. Thus, OPS measurements of photosensitizer concentrations can be used to assist in the scheduling of Pc 4-PDT.

Optimal conditions for successful ablation of high-grade dysplasia in Barrett's oesophagus using aminolaevulinic acid photodynamic therapy

Photodynamic therapy (PDT) using 5-aminolaevulinic acid (ALA-PDT) is an attractive alternative to PDT with porfimer sodium for the treatment of high-grade dysplasia (HGD) in Barrett's oesophagus (BO) because of the shorter duration of light photosensitivity and low risk of oesophageal stricture formation. Published results, however, show marked variation in its efficacy, and optimum treatment parameters have not been defined. This study investigated how the dose of ALA and the colour of the illuminating light influenced the biological effect. Twenty-seven patients were enrolled into a randomised controlled trial of red versus green (635 nm or 512 nm) laser light activation for the eradication of HGD with ALA-PDT in Barrett's oesophagus. A further 21 patients were subsequently treated with the most effective regimen. Regular endoscopic follow-up with quadrantic biopsies every 2 cm was performed. The primary outcome measure was eradication of HGD. Patient's receiving ALA at 30 mg/kg relapsed to HGD more than those receiving 60 mg/kg (P = 0.03). Additionally, for those treated with ALA 60 mg/kg, red laser light was more effective than green laser light (P = 0.008). Kaplan-Meier analysis of the 21 patients who were subsequently treated with this optimal regimen demonstrated an eradication rate of 89% for HGD and a cancer-free proportion of 96% at 36 months' follow-up. Using an ALA dose of 60 mg/kg activated by 1,000 J/cm red laser light, we found that ALA-PDT was a highly effective treatment for high-grade dysplasia in Barrett's oesophagus.

Analysis of differential PDT effect in rat bladder tumor models according to concentrations of intravesical hexyl-aminolevulinate

The hexylester of 5-aminolevulinic acid (HAL) is a very efficient precursor of the photosensitizer protoporphyrin IX (PpIX) for photodynamic therapy (PDT). Our previous study, performed in rat orthotopic bladder tumors, indicated an opposite effect of HAL/PpIX-PDT according to HAL concentration. The present study investigated possible reasons for this differential effect considering the impact of extracted amounts of PpIX in normal and tumor bearing bladders along with PpIX distribution in distinctive histopathological layers. High performance liquid chromatography (HPLC) analysis of tumor and normal bladder tissues after 8 mM and 16 mM HAL instillation showed that PpIX was the main porphyrin species. The PpIX production in tumor bladders instilled with 8 mM HAL was significantly higher than after 16 mM HAL. Fluorescence confocal microscopy demonstrated a punctuate bright fluorescence pattern in tumor zones of bladders instilled with 8 mM HAL, whereas a more diffuse cytoplasmatic fluorescence distribution was observed after 16 mM HAL instillation. Immunofluorescence staining together with transmission electron microscopy showed severe mitochondrial damage in tumor zones of bladders treated with 8 mM HAL/PpIX PDT, with intact mitochondria in tumor zones of bladders treated with 16 mM HAL/PpIX PDT. We conclude that the differential response to HAL/PpIX PDT in function of HAL concentrations could be attributed to diminished PpIX synthesis and differential intracellular localisation of PpIX. Mitochondria were shown to be the critical photodamaged sites of HAL/PpIX PDT and as such tissue sensitivity to treatment can be estimated through investigation of intracellular PpIX distribution.

EUS-guided photodynamic therapy with verteporfin for ablation of normal pancreatic tissue: a pilot study in a porcine model (with video)

BACKGROUND

EUS-guided photodynamic therapy (PDT) with the photosensitizing agent porfimer sodium has been shown to be effective in ablation of pancreatic tissue.

OBJECTIVE

The objective of this study was to determine the effectiveness and safety of EUS PDT with verteporfin, a photosensitizer associated with less photosensitivity.

DESIGN

Prospective investigation of 6 swine that received an IV injection of 6 mg/m2 of verteporfin before EUS.

SETTING

Hospital animal laboratory.

INTERVENTIONS

The tail of the pancreas was located with EUS and was used to guide the placement of a light catheter. The pancreatic tail was exposed to 10, 15, or 20 minutes of laser light (689 nm).

MAIN OUTCOME MEASUREMENTS

Follow-up abdominal CT, liver and renal function tests, and serum pancreatic enzymes levels were performed. Histology of the pancreas was obtained 7 days after the procedure on necropsy.

RESULTS

Localized tissue necrosis within the pancreatic tail (range 6.6-30.5 mm in diameter) was seen in all animals. The diameter of the necrotic tissue was directly related to the dose of light. No post-procedural complications were observed.

LIMITATIONS

Normal animal model (lack of malignant tissue).

CONCLUSIONS

EUS-guided PDT of porcine pancreas with verteporfin achieved localized pancreatic tissue ablation in a dose-related fashion.

Photodynamic therapy using 5-aminolaevulinic acid for the treatment of dysplasia in Barrett's oesophagus

BACKGROUND

5-Aminolaevulinic acid (ALA) is the naturally occurring metabolic precursor of an endogenously formed photosensitiser, protoporphyrin IX. It is used topically to treat benign and malignant skin disorders by a process called photodynamic therapy (PDT). Recently, data are emerging on its systemic use in the treatment of dysplasia in Barrett's oesophagus.

OBJECTIVE

To investigate the use of ALA-PDT for the treatment of dysplasia and early cancer in Barrett's oesophagus.

METHODS

A systematic literature review and synopsis is given.

CONCLUSION

ALA is an attractive alternative to the currently approved photosensitiser (porfimer sodium) due to its oral route of administration, shorter generalised skin photosensitivity period and lower rate of stricture formation. The studies presented demonstrate that ALA-PDT is both safe and effective for the treatment of dysplasia and early cancer in Barrett's oesophagus.

Photobleaching-based dosimetry predicts deposited dose in ALA-PpIX PDT of rodent esophagus

An improved method to estimate dose to esophageal tissue was investigated in the setting of photodynamic therapy with aminolevulinic acid-induced protoporphyrin IX (PpIX) treatment. A model of treatment-induced edema in the esophagus mucosa proved to be a well controlled and useful way to test the dosimetry model, and the light from the treatment laser together with the PpIX fluorescence intensity could be quantified reliably in real time. Dosimetry calculations based upon the detected fluorescence and bleaching kinetics were used to calculate the "effective" dose to the tissue, and a correlation was shown to exist between this metric and the edema induced in the esophagus. The difference between animals with no detectable treatment effect and those with significant edema was predictable based upon the dose calculation. The underlying assumption in the interpretation of the data is that rapid photobleaching of PpIX occurs when there is ample oxygen supply, and this bleaching is not present when oxygen is limited. This leads to the prediction that integration of the light and drug dose, in intervals where appreciable photobleaching occurs, should provide a prediction of the relative dose of singlet oxygen produced. This detection system and rodent model can be used for prospective dosimetry studies that focus on optimization of esophageal PDT.

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.

Photodynamic therapy: other uses

Mainstream uses for photodynamic therapy (PDT) in dermatology include nonmelanoma skin cancer and its precursors, acne vulgaris, photorejuvenation, and hidradenitis suppurativa. Many other dermatologic entities have been treated with PDT, including psoriasis, lichen planus, lichen sclerosus, scleroderma, cutaneous T cell lymphoma, alopecia areata, verruca vulgaris, Darier's disease and tinea infections. Nondermatologic applications include anal and vulva carcinoma, palliation of metastatic breast cancer to skin, Barrett's esophagus, and macular degeneration of the retina. PDT also has found to be useful in immunologic and inflammatory disorders, neoplasias other than skin cancer, and infections. The ability of this treatment to hone in on dysplastic epithelial and endothelial cells while retaining viability of surrounding tissue is its key feature because this leads to specific tumor destruction with cosmesis and function of the target organ intact.

Prostate PDT dosimetry

We provide a review of the current state of dosimetry in prostate photodynamic therapy (PDT). PDT of the human prostate has been performed with a number of different photosensitizers and with a variety of dosimetry schemes. The simplest clinical light dose prescription is to quantify the total light energy emitted per length (J/cm) of cylindrical diffusing fibers (CDF) for patients treated with a defined photosensitizer injection per body weight. However, this approach does not take into account the light scattering by tissue and usually underestimates the local light fluence rate, and consequently the fluence. Techniques have been developed to characterize tissue optical properties and light fluence rates in vivo using interstitial measurements during prostate PDT. Optical methods have been developed to characterize tissue absorption and scattering spectra, which in turn provide information about tissue oxygenation and drug concentration. Fluorescence techniques can be used to quantify drug concentrations and photobleaching rates of photosensitizers.

The effect of photodynamic therapy (PDT) on oesophageal motility and acid clearance in patients with Barrett’s oesophagus

BACKGROUND

Barrett's oesophagus is the major risk factor for oesophageal adenocarcinoma. It is proposed that long-term re-epithelialisation, which has been achieved following ablation using 5-aminolaevulinic acid (5-ALA) photodynamic therapy (PDT) may reduce the risk of malignant change. However, it is not known whether PDT modifies oesophageal motility.

AIM

To assess oesophageal pH and motility before and after PDT ablation in treated and untreated areas of the oesophagus.

METHODS

Twelve patients (10 male) with Barrett's oesophagus, median segment length 4 cm, were treated with PDT ablation. Twenty-four hours pH assessment and oesophageal manometry were performed before and 4-6 weeks after ablation. PDT was carried out using 635 nm red light, 4-6h after administration of 30 mg/kg 5-ALA. Proximal (untreated) and distal (treated) oesophageal resting pressure, wave amplitude, percentage peristalsis and percentage study time oesophageal pH<4, were assessed. Proton pump inhibitors (PPI) were administered throughout the study.

RESULTS

There were no significant differences in oesophageal motility in treated or untreated areas of the oesophagus after PDT compared to pre-treatment values. Patients who continued to experience oesophageal acid exposure required more treatments to achieve complete Barrett's ablation.

CONCLUSIONS

Oesophageal motility following ALA-PDT suggests a trend toward enhanced wave propagation however continued oesophageal acid exposure may affect PDT efficacy.

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.

Fluorescence Detection of Pleural Malignancies Using 5-Aminolaevulinic Acid

STUDY OBJECTIVE

Although the use of video-assisted thoracoscopy has improved the diagnostic accuracy in patients presenting with pleural diseases, not all biopsies performed are conclusive and staging of the disease is not always optimal. Fluorescence diagnosis (FD) with 5-aminolaevulinic acid (5-ALA) has been used in the diagnostic workup for various malignancies. The impact of 5-ALA-mediated FD on diagnosis and staging during video-assisted thoracoscopy was examined.

DESIGN

Prospective, single-center study.

SETTING

National cancer center.

PATIENTS

Twenty-six patients with nonconclusive pleural effusions who were scheduled for video-assisted thoracoscopy.

INTERVENTION

Eligible patients were administered 1,500 to 2,500 mg po of 5-ALA before video-assisted thoracoscopy. After conventional inspection with white light, fluorescence inspection of the pleural cavity was performed (D-LIGHT Auto Fluorescent System; Karl Storz; Tuttlingen, Germany). Biopsy specimens of both normal and abnormal sites, as determined from white light and FD inspection, were obtained for histologic examination.

RESULTS

One patient was ineligible, and two patients were not evaluable because of equipment failure. One postoperative death occurred due to preexisting myocardial disease. In another patient, an empyema developed; in another patient, a postoperative infection of the lung developed. Other toxicities were minimal. A definitive diagnosis was obtained in 24 of 25 cases, with malignant mesothelioma in 15 cases, other malignancies in 5 cases, one infection, and three benign diseases. Upstaging occurred in four patients (unsuspected tumor deposits) due to FD examination. In 23 patients, a total of 111 biopsy specimens could be analyzed. When correct findings of white light and FD were compared, FD had an additional value in 21 of 111 biopsies, compared to white light with 16 of 111 biopsies.

CONCLUSIONS

FD using 5-ALA in the pleural cavity is feasible with limited side effects when used in addition to white light inspection. It improved visualization of abnormal lesions and led to upstaging in 4 of 15 mesothelioma patients.

Light dosimetry measurements during ALA-PDT of Barrett's oesophagus

A fibre optic probe and compact light detection system has been used to monitor the fluence-rate at the tissue surface during 5-aminolaevulinic acid based photodynamic therapy (PDT) of Barrett's oesophagous. The contributions from three specific wavelengths were recorded, corresponding to the combination of therapeutic laser light and fluorescence emission from protoporphyrin IX (635nm), the fluorescence from an oxidation product of the photosensitiser (670nm), and the protoporphyrin IX fluorescence alone (705nm). We have found that light scattering results in an enhancement of the therapeutic fluence-rate, and hence light dose, by approximately 70%. At the onset of therapy the fluorescence provides a 10% contribution to the overall fluence-rate at 635nm. The dynamics of photosensitiser bleaching could be extracted from the depletion in light signals. By defining a bleaching dose as the 635nm light fluence delivered over the period during which the photosensitiser fluorescence decays to 1/e(3) of its initial value, we find that the average ratio of bleaching to total dose is 33%. Further, the fluorescence contributes approximately 5% of the bleaching light dose. These results suggest that the prescribed period of therapeutic light exposure may be reduced with no loss in clinical efficacy, but with a consequent improvement in patient tolerance to this therapy.

Laser Ablation Therapies for Barrett’s Esophagus

The metaplastic change of the normal squamous epithelium of the distal esophagus into a specialized columnar epithelium is known as Barrett's esophagus (BE) and is associated with an increased risk of adenocarcinoma of the esophagus. It is a frequent complication of gastroesophageal reflux disease (GERD) and up to 10% of patients with GERD suffer from BE. The progression to dysplasia increases the risk of cancer development and the annual risk of developing cancer in Barrett's esophagus is estimated to be 0.5% per year. The management of BE with high grade dysplasia (HGD) is controversial. Recent innovations in endoscopic therapy have allowed for the development of multiple endoscopic techniques, such as photodynamic therapy (PDT), argon plasma coagulation (APC), and endoscopic mucosal resection. In this article, we will discuss primarily photodynamic therapy, and other ablative technologies such as argon plasma coagulation in the treatment of BE.

Determination of optical properties of normal and adenomatous human colon tissues in vitro using integrating sphere techniques

AIM: The purpose of the present study is to compare the optical properties of normal human colon mucosa/submucosa and muscle layer/chorion, and adenomatous human colon mucosa/submucosa and muscle layer/chorion in vitro at 476.5, 488, 496.5, 514.5 and 532 nm. We believe these differences in optical properties should help differential diagnosis of human colon tissues by using optical methods.

METHODS: In vitro optical properties were investigated for four kinds of tissues: normal human colon mucosa/submucosa and muscle layer/chorion, and adenomatous human colon mucosa/submucosa and muscle layer/chorion. Tissue samples were taken from 13 human colons (13 adenomatous, 13 normal). From the normal human colons a total of 26 tissue samples, with a mean thickness of 0.40 mm, were used (13 from mucosa/submucosa and 13 from muscle layer/chorion), and from the adenomatous human bladders a total of 26 tissue samples, with a mean thickness of 0.40 mm, were used (13 from mucosa/submucosa and 13 from muscle layer/chorion). The measurements were performed using a double-integrating-sphere setup and the optical properties were assessed from these measurements using the adding-doubling method that was considered reliable.

RESULTS: The results of measurement showed that there were significant differences in the absorption coefficients and scattering coefficients between normal and adenomatous human colon mucosa/submucosa at the same wavelength, and there were also significant differences in the two optical parameters between both colon muscle layer/chorion at the same wavelength. And there were large differences in the anisotropy factors between both colon mucosa/submucosa at the same wavelength, there were also large differences in the anisotropy factors between both colon muscle layer/chorion at the same wavelength. There were large differences in the value ranges of the absorption coefficients, scattering coefficients and anisotropy factors between both colon mucosa/submucosa, and there were also large differences in these value ranges between both colon muscle layer/chorion. There are the same orders of magnitude in the absorption coefficients for four kinds of colon tissues. The scattering coefficients of these tissues exceed the absorption coefficients by at least two orders of magnitude.

CONCLUSION: There were large differences in the three optical parameters between normal and adenomatous human colon mucosa/submucosa at the same laser wavelength, and there were also large differences in these parameters between both colon muscle layer/chorion at the same laser wavelength. Large differences in optical parameters indicate that there were large differences in compositions and structures between both colon mucosa/submucosa, and between both colon muscle layer/chorion. Optical parameters for four kinds of colon tissues are wavelength dependent, and these differences would be useful and helpful in clinical applications of laser and tumors photodynamic therapy (PDT).

Endoscopic ablation of Barrett's oesophagus: a randomized-controlled trial of photodynamic therapy vs. argon plasma coagulation

BACKGROUND

Barrett's oesophagus is the major risk factor for oesophageal adenocarcinoma. 5-Aminlevulinic acid-induced photodynamic therapy and argon plasma coagulation have been shown to be effective for ablating Barrett's oesophagus, but a comparative trial of these two modalities has not been reported.

AIMS

To compare photodynamic therapy and argon plasma coagulation for the ablation of Barrett's oesophagus.

METHODS

A total of 68 patients (54 male, 14 female; median age 61) with Barrett's oesophagus were randomized to photodynamic therapy (n = 34) or argon plasma coagulation (n = 34). Photodynamic therapy was performed using 5-aminlevulinic acid (30 mg/kg) and red light. Argon plasma coagulation was administered at a power setting of 65 W. Multiple treatment sessions were performed, with follow-up to 24 months.

RESULTS

All patients showed a macroscopic reduction in the area of Barrett's oesophagus. This was greatest in the argon plasma coagulation group with 33 of 34 (97%) ablated, compared with 17 of 34 (50%) in the photodynamic therapy group; in the remainder, there was a reduction in the length of Barrett's oesophagus (median 50%, range: 5-90). Buried glands were found in 24% of photodynamic therapy patients, and in 21% of argon plasma coagulation patients. The median follow-up is 12 months (range: 6-24).

CONCLUSIONS

Photodynamic therapy and argon plasma coagulation are both effective for ablating Barrett's oesophagus. Argon plasma coagulation appears more effective than photodynamic therapy, but the impact of both on carcinoma development requires larger studies with long-term follow-up.