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Background: Patients with pancreatic cancer have a poor prognosis apart from the few suitable for surgery. Photodynamic therapy (PDT) produces localised tissue necrosis but previous studies using the photosensitiser meso-tetrahydroxyphenylchlorin (mTHPC) caused prolonged skin photosensitivity. This study assessed a shorter acting photosensitiser, verteporfin. Methods: Fifteen inoperable patients with locally advanced cancers were sensitised with 0.4 mg kg−1 verteporfin. After 60–90 min, laser light (690 nm) was delivered via single (13 patients) or multiple (2 patients) fibres positioned percutaneously under computed tomography (CT) guidance, the light dose escalating (initially 5 J, doubling after each three patients) until 12 mm of necrosis was achieved consistently. Results: In all, 12 mm lesions were seen consistently at 40 J, but with considerable variation in necrosis volume (mean volume 3.5 cm3 at 40 J). Minor, self-limiting extrapancreatic effects were seen in multifibre patients. No adverse interactions were seen in patients given chemotherapy or radiotherapy before or after PDT. After PDT, one patient underwent an R0 Whipple's pancreaticoduodenectomy. Conclusions: Verteporfin PDT-induced tumour necrosis in locally advanced pancreatic cancer is feasible and safe. It can be delivered with a much shorter drug light interval and with less photosensitivity than with older compounds.

Photodynamic therapy (PDT) is already being used in the treatment of many cancers. This review examines its components and the new developments in our understanding of its immunological effects as well as pre-clinical and clinical studies, which have investigated its potential use in the treatment of breast cancer.

Protoporphyrin IX (PpIX)-induced photodynamic therapy (PDT) is being utilised within dermatological practice as a topical method of localised ablation of nonmelanoma skin cancer/precancer. Standardised protocols have been implemented to good effect when the disease remains superficial but improvement is required to widen the application of this light activated drug therapy to treat thicker or acrally located conditions. As innate haem biosynthesis is exploited to accumulate the light sensitive PpIX from a topically applied inert prodrug (aminolaevulinic acid; ALA), this pathway can be further manipulated through the concurrent administration of an iron chelating agent to hyper-accumulate PpIX by temporarily reducing its iron dependent conversion to haem. A topical preparation of ALA was applied to normal rat skin with or without the hydroxypyridinone iron chelator, CP94. Image analysis quantification of tissue fluorescence following excision indicated that ALA plus CP94 produced 29.0% more fluorescence than ALA alone (p < 0.09), peaking at 5 hours. Furthermore, fluorescence spectroscopy of frozen skin samples from each treatment group were characteristic of PpIX (maxima 636 +/- 2 nm), indicating that topical CP94 administration elevated PpIX levels without significantly producing any other fluorescent species. When PDT efficacy was considered post irradiation, a substantial three-fold increase in effect was observed 4 days after treatment when the iron chelator CP94 was co-administered topically with the prodrug (p < 0.07). It has therefore been established that the hydroxypyridinone CP94, is topically active within normal rat skin, effectively chelating iron to elevate PpIX accumulation and thus improve PDT efficacy.

Endoscopic radiofrequency ablation (RFA) is an effective treatment for high-grade dysplasia in Barrett's esophagus in ablation-naïve patients, but no studies have evaluated its use in patients in whom ablative therapy has previously failed. We describe 14 patients with residual high-grade dysplasia following aminolevulinic acid or Photofrin (porfimer sodium) photodynamic therapy (PDT). An overall complete reversal of dysplasia was achieved in 86 % with a combination of RFA and rescue endoscopic mucosal resection. The median total follow-up is 19 months. The rate of strictures was 7 % (1/14) and there was a low rate of buried glands (0.5 % follow-up biopsies). These data suggest RFA is both safe and effective for eradication of high-grade dysplasia in patients in whom PDT has failed.

Background and aims: DNA ploidy abnormalities (aneuploidy/tetraploidy) measured by flow cytometry (FC) are strong predictors of future cancer development in untreated Barrett's oesophagus, independent of histology grade. Image cytometric DNA analysis (ICDA) is an optical technique allowing visualisation of abnormal nuclei that may be undertaken on archival tissue. Our aim was to determine the accuracy of ICDA vs FC, and evaluate DNA ploidy as a prognostic biomarker after histologically successful treatment with photodynamic therapy (PDT). Methods: Nuclei were extracted from 40 μm sections of paraffin-embedded biopsies and processed for ICDA at UCL and FC at UW using standardised protocols. Subsequently, DNA ploidy was evaluated by ICDA on a cohort of 30 patients clear of dysplasia 1 year after aminolaevulinic acid PDT for high-grade dysplasia (HGD). The results were correlated with long-term outcome. Results: In the comparative study, 93% (41 out of 44) of cases were classified identically. Errors occurred in the near-diploid region by ICDA and the tetraploid region by FC. In the cohort study, there were 13 cases of late relapse (7 cancer, 6 HGD) and 17 patients who remained free of dysplasia after a mean follow-up of 44 months. Aneuploidy post-PDT was highly predictive for recurrent HGD or cancer with a hazard ratio of 8.2 (1.8–37.8) (log-rank P=0.001). Conclusions: ICDA is accurate for the detection of DNA ploidy abnormalities when compared with FC. After histologically successful PDT, patients with residual aneuploidy are significantly more likely to develop HGD or cancer than those who become diploid. DNA ploidy by ICDA is a valuable prognostic biomarker after ablative therapy.

Background and Objectives: Prostate cancer is increasing in incidence, but current treatments including surgery and radiotherapy have significant side effects. This pilot study was designed to assess the potential of photodynamic therapy (PDT) using meso tetra hydroxy phenyl chlorin (mTHPC) for organ confined prostate cancer. Study Design/Patients and Methods: Six men with organ confined prostate cancer were photosensitised with mTHPC (0.15 mg/kg). Between 2 and 5 days later, red light (652 nm) was delivered to areas of biopsy proven cancer via fibres inserted through transperineal needles (50–100 J per site). Results: After 8 of 10 PDT sessions, the prostate specific antigen (PSA) fell by up to 67%. Early MRI scans showed oedema and patchy necrosis, which resolved over 2 months. Biopsies of treated areas revealed necrosis and fibrosis at 1–2 months. Conclusions: PDT for primary prostate cancer appears safe and can reduce PSA levels. As this was a phase I study, no attempt was made to treat the whole prostate; this or targeted tumour ablation could be attempted in a phase II study with an increased number of fibres. This technique merits further investigation in early prostate cancer. Lasers Surg. Med. 38:356–363, 2006. 2006 Wiley-Liss, Inc.

ObjectivesPhotodynamic therapy (PDT, the combination of light with a photosensitising drug in the presence of oxygen) inhibits restenosis after angioplasty without stenting. This study assesses the potential of PDT for prevention of in-stent re-stenosis.Design and methodsNormal rabbits were given the photosensitising agent 5-aminolaevulinic acid (ALA) 60mg/kg, 3h prior to endovascular illumination of the iliac artery (635nm at 50J/cm2) either immediately before or after deployment of an oversized (3mm diameter) stent. PDT treated arteries were retrieved 3 or 28 days later and assessed for cell counts and vascular morphometry. Control arteries (stent but no PDT) were examined at 28 days.ResultsThere were no adverse events and all vessels were patent at the end of the study. At 3 days there was almost complete medial cell ablation when light was delivered before stent deployment (17±1cells/hpf), with little effect when illumination followed stent deployment (184±17cells/hpf, p

Photochemical internalisation (PCI) is a technique for releasing biologically active macromolecules from endocytic vesicles by light activation of a photosensitiser localised in the same vesicles of targeted cells. This study investigated the PCI of the toxin gelonin as a way of enhancing the effect of photodynamic therapy (PDT) on a human malignant fibrous histiocytoma transplanted into nude mice using the photosensitiser disulphonated aluminium phthalocyanine (AlPcS(2a)). Pharmacokinetic studies after intraperitoneal administration showed that the serum level of AlPcS(2a) fitted a biexponential model (half-lives of 1.8 and 26.7 h). The tumour concentration was roughly constant up to 48 h, although fluorescence microscopy showed that the drug location was initially mainly vascular, but became intracellular by 48 h. To compare PDT with PCI, 48 h after intraperitoneal injection of 10 mg kg(-1) AlPcS(2a), and 6 h after direct intratumour injection of 50 microg gelonin (PCI) or a similar volume of phosphate-buffered saline (PDT controls), tumour-bearing animals were exposed to red light (150 J cm(-2)). Complete response was observed for more than 100 days in 50% of the PCI tumours but only 10% of the PDT tumours (P0.01). In tumours examined histologically 4 days after light delivery, the depth of necrosis was 3-4 mm after PDT, but 7 mm after PCI. The deeper effect after PCI demonstrates that the light fluence needed to kill tumour is less than with PDT. We conclude that PCI with gelonin can markedly enhance the effect of PDT on this type of tumour and may have a role clinically as an adjunct to surgery to control localised disease.

Interstitial photodynamic therapy (IPDT) is a technique for applying photodynamic therapy (PDT) to internal tumours using light delivered via fibres inserted percutaneously. This phase I-II study assessed the safety and efficacy of IPDT for patients with persistent or recurrent head and neck cancer unsuitable for further treatment with surgery, radiotherapy or chemotherapy, recruited for 'last hope' salvage treatment. Patients were sensitised with 0.15 mg kg(-1) mTHPC (meso-tetrahydroxyphenyl chlorin) 4 days prior to light delivery from fibres inserted directly into the target tumour (20 J per site at 652 nm) under image guidance. In all, 45 patients were treated. Nine achieved a complete response. Five are alive and free of disease 10-60 months later. Symptomatic relief (mainly for bleeding, pain or tumour debulking) was achieved in a further 24. The median survival (Kaplan-Meier) was 16 months for the 33 responders, but only 2 months for the 12 nonresponders. The only serious complication was a carotid blow out 2 weeks after PDT. No loss of function was detected in nerves encased by treated tumours. Interstitial photodynamic therapy provides worthwhile palliation with few complications and occasional long-term survivors for otherwise untreatable advanced head and neck cancers. It is a treatment option worth adding to those available to integrated head and neck oncology teams.

Photodynamic therapy (PDT) requires a photosensitising drug, light and oxygen. While it is known that the haemoglobin oxygen saturation (HbSat) can be altered by PDT, little has been done to correlate this with microvascular changes and the final biological effect. This report describes such studies on the normal liver of rats sensitised with aluminium disulphonated phthalocyanine. In total, 50 J of light at 670 nm, continuous or fractionated at 25 or 100 mW, was applied with a single laser fibre touching the liver surface. HbSat was monitored continuously 1.5-5.0 mm from the laser fibre using visible light reflectance spectroscopy (VLRS). Vascular shutdown was assessed by fluorescein angiography 2-40 min after light delivery. Necrosis was measured at post mortem 3 days after PDT. In all treatment groups at a 1.5 mm separation, HbSat fell to zero with little recovery after light delivery. At 2.5 mm, HbSat also decreased during light delivery, except with fractionated light, but then recovered. The greatest recovery of fluorescein perfusion after PDT was seen using 25 mW, suggesting an ischaemia/reperfusion injury. Necrosis was more extensive after low power and fractionated light than with 100 mW, continuous illumination. We conclude that VLRS is a useful technique for monitoring HbSat, although the correlation between HbSat, fluorescein exclusion and necrosis varied markedly with the light delivery regimen used.

Watermelon stomach (gastric antral vascular ectasia) is a rare cause of gastric bleeding which can render patients transfusion-dependent. Laser therapy can be used to stop bleeding but the long-term success of this approach is not well described. We present a retrospective analysis of 24 consecutive transfusion-dependent patients who were treated in a national referral centre with Nd:YAG laser over an 18 year period. Laser therapy stopped all bleeding in 20 patients (83%) after a median of two sessions. Median follow up was 55 months (range 9-127). Patients remained transfusion free for a median of 16 months and a second course of treatment succeeded in all those who re-bled. One gastric perforation occurred early in the series and two patients developed pyloric stenosis which was successfully treated with balloon pyloric dilatation. Oestrogens were not used in these patients. Our experience shows that long-term remission from blood transfusion is seen in most patients treated with Nd:YAG laser. If bleeding recurs, further laser treatment is usually successful.

Reperfusion injury can occur when blood flow is restored after a transient period of ischaemia. The resulting cascade of reactive oxygen species damages tissue. This mechanism may contribute to the tissue damage produced by 5-aminolaevulinic acid-induced photodynamic therapy, if this treatment temporarily depletes oxygen in an area that is subsequently reoxygenated. This was investigated in the normal colon of female Wistar rats. All animals received 200 mg kg−1 5-aminolaevulinic acid intravenously 2 h prior to 25 J (100 mW) of 628 nm light, which was delivered continuously or fractionated (5 J/150 second dark interval/20 J). Animals were recovered following surgery, killed 3 days later and the photodynamic therapy lesion measured macroscopically. The effects of reperfusion injury were removed from the experiments either through the administration of free radical scavengers (superoxide dismutase (10 mg kg−1) and catalase (7.5 mg kg−1) in combination) or allopurinol (an inhibitor of xanthine oxidase (50 mg kg−1)). Prior administration of the free radical scavengers and allopurinol abolished the macroscopic damage produced by 5-aminolaevulinic acid photodynamic therapy in this model, regardless of the light regime employed. As the specific inhibitor of xanthine oxidase (allopurinol) protected against photodynamic therapy damage, it is concluded that reperfusion injury is involved in the mechanism of photodynamic therapy in the rat colon. British Journal of Cancer (2002) 86, 989–992. DOI: 10.1038/sj/bjc/6600178 www.bjcancer.com © 2002 Cancer Research UK

The major limitation of the long term success of percutaneous coronary interventions is the development of restenosis, which occurs in 30–50% of patients within six months.1 2 Restenosis is the result of a complex pathophysiological process in the arterial wall in response to balloon dilatation or stent insertion. For many years the hallmark of this response to injury was considered to be the development of intimal hyperplasia resulting from the proliferation and migration of smooth muscle cells from the arterial media.3More recently, it has become clear that this is not the only factor involved. Other key aspects in the development of the restenotic lesion are the extracellular matrix, elastic vessel recoil, and arterial remodelling.4 While our understanding of the processes induced by balloon injury has improved, treatment strategies to limit this have been disappointing in clinical practice.5Stenting, which is now used in up to 80% of all coronary interventional procedures, has almost eliminated problems from elastic recoil and has reduced restenosis rates, but neointimal hyperplasia around stent struts can still lead to in-stent restenosis.6 Intracoronary brachytherapy is one technique that has proved promising in the prevention of restenosis using either catheter based systems for radiation delivery or radioactive stents.7 Concerns have been expressed about late thrombotic occlusion after brachytherapy.8 However, the prolonged use of antiplatelet drugs may control this problem. Brachytherapy is probably the best option for treating restenosis currently available. Nevertheless, it would be attractive to find a method of preventing restenosis after percutaneous intervention that does not involve ionising radiation or prolonged drug treatment. Photodynamic therapy (PDT), which in contrast to brachytherapy uses non-ionising radiation, is emerging as another possible strategy. PDT involves the interaction of a photosensitising drug, light, and tissue oxygen9 (fig 1). Photosensitising agents, many …

Currently, the clinical use of 5-aminolaevulinic acid (ALA) induced protoporphyrin IX (PPIX) for photodynamic therapy (PDT) is limited by the maximum tolerated oral ALA dose (60 mg/kg). Attempts have been made to enhance this treatment modality without increasing the administered dose of ALA. One way to do this is through light dose fractionation, where the irradiation is interrupted at a particular point for a short period of time. This can produce up to three times more necrosis than with the same light dose delivered without a break. An oxygen microelectrode was employed to study the effect of continuous and fractionated light regimes on the level of oxygen in the colon of normal Wistar rats during ALA PDT. A rapid decline in pO2 occurred close to the irradiation fibre as soon as the light dose commenced. With the fractionated regime, a partial recovery in pO2 was observed during the dark interval which was reversed soon after the second light fraction commenced. We have shown that the level of tissue oxygen at the treatment site is affected differently when the light dose is fractionated, than when continuous illumination is employed. This factor may at least partially explain the difference in outcome of these two treatment regimes. Further, oxygen measurements might prove to be a useful way of monitoring PDT treatments if they can predict whether tissue is likely to be viable following treatment.

Topical or systemic administration of 5-aminolaevulinic acid results in biosynthesis of the photosensitiser protoporphyrin IX (PpIX) with some selectivity for malignant lesions. Excitation near 400 nm excites both intrinsic green tissue autofluorescence and red fluorescence from PpIX which may be exploited for the optical diagnosis of malignant and premalignant disease. In this work the utility of a cooled 12-bit single chip charge-coupled device (CCD) colour camera was investigated for photodiagnostic fluorescence ratio imaging. The red to green fluorescence intensity ratios were calculated for each pixel in real-time and fluorescence ratio images were displayed typically at a rate of 2 frames/s. Laboratory tests of fluorescence ratio imaging showed good contrast enhancement between control tissues and tissue phantoms and those containing porphyrin photosensitisers. In preliminary clinical tests, a clear demarcation between neoplastic/cancerous lesions and adjacent normal tissue was demonstrated. The extent of PpIX photobleaching during photodynamic therapy was also investigated using fluorescence ratio imaging.

Cylindrical light diffusers are commercially available for clinical applications such as photodynamic therapy (PDT) and interstitial laser photocoagulation (ILP). A fluorescence imaging technique has been used to quantify the light distribution produced by each of six different diffuser fibres. The light distribution produced by each device was found to depend on the distance the light propagated in the fluorescent dye solution. At a distance of 1 mm from the diffuser midline, the measured profiles were found to be consistent with published results obtained in air at a similar distance. The three devices intended for PDT utilised scattering particles and reflectors in their construction. The profiles produced by these applicators revealed peaks that were attributed to the reflectors located at their distal tips. By comparison, the two etched ILP fibres displayed either a strong modulation in the profile due to non-uniform etching or a predominant forward peak associated with the conical shape of the tip. We conclude that it is important to take into account the forward-directed light emitted by the diffusers when considering clinical applications using these devices.

Background Photodynamic therapy (PDT) reduces neointimal hyperplasia and negative remodelling following balloon injury in small and large animal models. This clinical study investigated the role of adjuvant PDT following femoral percutaneous transluminal angioplasty (PTA). Methods Eight PTAs in seven patients (two women) with a median age of 70 (range 59–86) years were performed with adjuvant PDT. All patients had previously undergone conventional angioplasty at the same site which resulted in symptomatic restenosis or occlusion between 2 and 6 months. Each was sensitized with oral 5-aminolaevulinic acid 60 mg/kg, 5–7 h before the procedure. Following a second femoral angioplasty, up to 50 J/cm2 red light (635 nm) was delivered to the angioplasty site via a laser fibre within the angioplasty balloon. Patients were kept in subdued light overnight and discharged the following day. Outcome was assessed by duplex imaging at 24 h, 1, 3 and 6 months and by intravenous digital subtraction angiography at 6 months. A peak systolic velocity ratio (PSVR) of more than 2·0 at the angioplasty site was taken to represent restenosis. Results All patients tolerated the procedure well without adverse complications or death. All were rendered asymptomatic which was sustained throughout the study interval. All vessels remained patent and no lesion attained the duplex definition of restenosis. Median (interquartile range) PSVR across stenotic segments was 4·7 (3·7–5·7) before angioplasty, 1·1 (0·9–1·3) at 24 h and 1·4 (1·0–1·8) at 6 months after intervention (P = 0·04 compared with preoperative value). Conclusion This pilot study suggests that endovascular PDT is safe and may reduce restenosis following angioplasty. The data justify a randomized controlled trial.

Fibroadenomas are benign lesions of the breast that are common in young women. Most can safely be treated conservatively, but if they are not excised, the majority persist for several years and some increase in size. Interstitial Laser Photocoagulation is a new approach to treating these lesions. Under local anaesthesia and sedation, using ultrasound guidance, fine needles are inserted into the fibroadenoma and a laser fibre passed through each needle to coagulate the lesion in situ. Twenty-nine lesions (diameter 14–35 mm) have been treated in 24 patients. Twenty eight (97%) shrank in size on follow up ultrasound assessment. Fourteen were followed for a year, at which time none was palpable and only one could still be detected on ultrasound. In early cases there were three minor complications (a small scar at a site of needle insertion), later prevented by improved technique. This is a simple and safe outpatient procedure for ablating fibroadenomas that does not require open surgery.

Objectives: to test the hypothesis that intravascular light could be delivered via a balloon catheter for arterial photodynamic therapy (PDT). Design: pig non-injury model. Materials: clinical catheter equipment. Methods: large White pigs (15–20 μg) were photosensitised with 5-aminolaevulinic acid (5-ALA) induced protoporphyrin IX (PpIX) at a concentration of 120mg/kg. Arterial biopsies were taken at intervals between 30 mins and 24h and frozen sections analysed using a CCD camera to give a temporal profile of fluorescence in each arterial layer. PDT was given to normal arterial segments via a 4mm transparent PTA balloon inflated so as to occlude flow, but not distend the artery. Animals were culled at 3 and 14 days and the above segments harvested. Results: fluorescence peaked in the adventitia, intima and medial layers at 1.5, 4 and 6h respectively. PDT at all time points produced VSMC depletion compared with controls. The degree of depletion mirrored the fluorescence profile of PpIX. Conclusions: PDT can be delivered via a standard PTA balloon with a transparent channel. This depletes the VSMC population within the arterial wall without complications. Intra-arterial PDT is therefore a potential therapy to reduce the incidence of restenosis post-angioplasty.

Tissue oxygenation is one of the key dosimetric factors involved in the application of photodynamic therapy (PDT). However, quantitative studies of oxygenation levels at and surrounding the treatment site have been lacking both before, during and after treatment. With the recent development of sensitive, non-invasive, optical spectroscopic techniques based on oxygen-dependent phosphorescence quenching of probe compounds, oxygenation levels can now be measured quantitatively at selected sites with spatial resolution on the millimeter scale. We present results using the phosphorescent compound, palladium meso-tetra(carboxyphenyl)porphine, for measurement of in vivo microvascular oxygen tensions in rat liver during PDT. Time-resolved phosphorescence detection was carried out using fibre-optic sensoring, and oxygen tensions were determined from the phosphorescence lifetimes using Stern-Volmer analysis. During PDT treatment using 5-aminolaevulinic (ALA) acid-induced protoporphyrin IX (PPIX) with a 50 mg/kg ALA dose, oxygen levels near the irradiation fibre placed on the surface of the liver showed a significant decrease by a factor of ten from 20 to 2 torr after an energy dose of 60 J using 100 mW at 635 nm. Areas farther from the treatment site which were exposed to lower light doses exhibited lower reductions in oxygen levels. This spectroscopic technique is a highly sensitive means of investigating tissue oxygenation during and after treatment, and should help not only to advance the understanding of hypoxia and microvascular damage in the PDT mechanism but also contribute to improving the dosimetry of PDT.

Currently, the clinical use of 5-aminolaevulinic acid (ALA)-induced protoporphyrin IX (PPIX) for photodynamic therapy (PDT) is limited by the maximum tolerated oral ALA dose (60 mg kg(-1)). This study investigates whether hydroxypyridinone iron-chelating agents can be used to enhance the tissue levels of PPIX, without increasing the administered dose of ALA. Quantitative charge-coupled device (CCD) fluorescence microscopy was employed to study PPIX fluorescence pharmacokinetics in the colon of normal Wistar rats. The iron chelator, CP94, when administered with ALA was found to produce double the PPIX fluorescence in the colonic mucosa, compared with the same dose of ALA given alone and to be more effective than the other iron chelator studied, CP20. Microspectrofluorimetric studies demonstrated that PPIX was the predominant porphyrin species present. PDT studies conducted on the colonic mucosa showed that the simultaneous administration of 100 mg kg(-1) CP94 i.v. and 50 mg kg(-1) ALA i.v. produced an area of necrosis three times larger than similar parameters without the iron-chelating agent with the same light dose. It is possible, therefore, to increase the amount of necrosis produced by ALA-induced PDT substantially, without increasing the administered dose of ALA, through the simultaneous administration of the iron-chelating agent, CP94.

Helicobacter pylori has been associated with peptic ulcers, gastric cancer and various other gastroduodenal pathologies. Conventional antibiotic treatment is not entirely satisfactory, whereas photodynamic therapy (PDT) is a possible alternative. Although PDT has been shown to be effective in killing helicobacter on native gastric mucosa, the success of the technique will depend upon the mucosa underlying the bacteria remaining unharmed. This study examined the effect of increasing doses of low-power laser light on rat gastric mucosa, sensitized with either methylene blue (MB), haematoporphyrin derivative (HpD) or toluidine blue (TBO). No damage was detectable with any of the photosensitizers when a light dose of 250 Jcm-2 was used. Mucosal damage was seen consistently with TBO (1 mg ml-1) and a light dose of 500 J cm-2. The same light dose of 500 J cm-2 using MB caused inconsistent damage to the mucosa, whereas HpD had no effect even with the highest dose of laser light (500 J cm-2). As the energy doses required to kill bacteria (50 and 200 Jcm-2 for MB and TBO, respectively) are well below the levels shown to damage normal gastric mucosa, PDT forH. pylori should not be harmful to the underlying epithelium.

Pancreatic cancer is difficult to treat, even for tumours localized to the pancreas. Photodynamic therapy (PDT) is a non-thermal technique for producing localized tissue necrosis with light after prior administration of a photosensitizing drug and it could have a role in the local treatment of these cancers. We studied PDT in a transplanted cancer in the hamster pancreas using the photosensitizer mTHPC (meta-tetrahydroxyphenylchlorin). Fluorescence microscopy showed maximum levels of mTHPC in normal pancreas 2-4 days after sensitization and in tumour at 4-5 days. For PDT, animals were given 0.1 or 0.3 mg kg(-1) mTHPC and the tumour was treated at laparotomy 2 or 4 days later with red light (50 J at 650 nm, continuous or fractionated) delivered via a single fibre touching the tumour surface. The maximum zone of tumour necrosis (seen 3 days after PDT) was 8.7 mm in diameter with continuous irradiation, increasing to 12.4 mm with light fractionation (four equal fractions with 3 min between fractions). The main complication was sealed duodenal perforation, seen in 3 of 16 animals, probably due to inadequate shielding of the duodenum from the light. The duodenal problems seen in hamsters are unlikely to cause trouble in the much thicker human duodenum. PDT tumour necrosis in this animal model has now been shown with a range of photosensitizers, but mTHPC is attractive as it is likely to produce the largest volumes of necrosis around each treatment point with short light exposure times. This technique could have a role in the treatment of localized cancers of the pancreas in patients unsuitable for surgery and can now be considered for preliminary clinical trials. Images Figure 2 Figure 3

SummaryAim - To correlate the magnetic resonance imaging signal changes observed during interstitial laser photocoagulation (ILP) therapy with histopatho-logical analysis of tissue necrosis. A 1.5T MR system was used. Lesions were produced with a diode laser (805 nm) in the liver of normal Wistar rats at laparotomy under general anaesthesia and imaged during treatment. Seventeen lesions were monitored with a T1-weighted spin echo (T1WSE) sequence, and 15 with a FLASH sequence. Treated tissue was removed and stained for NADPH-diaphorase to determine the extent of devitalization. Per-procedural T1WSE showed an expanding area of low signal which developed a high signal rim as ILP progressed. FLASH imaging showed an expanding area of low intensity which was replaced by a complex region of signal change as treatment progressed. Good imaging-histopathological correlation was shown: for T1WSE, r2=0.88 (P < 0.001) and for FLASH, r2=0.95 (P < 0.001). MR imaging during hepatic ILP accurately shows the extent of tis...

Background and Objective Photodynamic therapy (PDT) using 5-aminolevulinic acid (ALA)-induced protoporphyrin IX (PpIX) for sensitization is a promising treatment for carcinoma in situ and diffuse premalignant changes of the bladder. We studied the biodistribution of PpIX in a range of tissues with oral and intravesical routes of administration of ALA and compared the photodynamic effects on bladder and skin. Study Design/Materials and Methods: Normal Wistar rats were given oral or intravesical ALA and PpIX levels in the liver, kidney, skin, and bladder measured by fluorescence microscopy on tissue sections. At the time of maximum PpIX levels, the bladder and skin on the back were illuminated with light at 630 nm and the PDT effects compared. Results PpIX fluorescence in the urothelium after 200 mg/kg given intravesically was comparable to that found after 100 mg/kg orally. The ratio of PpIX levels between the urothelium and the underlying muscle was the same for both routes of administration, although there appeared to be more selectivity of urothelial PDT necrosis after intravesical administration. Skin photosensitization was greater after oral ALA, the epidermal PpIX level being three times higher than after intravesical administration for comparable urothelial levels and the PDT effect being more marked. Conclusions Intravesical instillation is preferable to oral administration of ALA for PDT ablation of the urothelium of the rat bladder without damage to the underlying tissue layers and for minimizing skin photosensitivity. The technique is now ready for clinical trials. Lasers Surg. Medicine 20:254–264, 1997. © 1997 Wiley-Liss, Inc.

SummaryInterstitial laser photocoagulation (ILP) is currently limited by deficient per-procedural monitoring. The purpose of this study was to evaluate MR control of ILP of hepatic metastases. Twenty-two laser activations were used to treat eight metastases in seven patients under local anaesthesia and sedation. Laser energy was delivered via optical fibres positioned in the tumour under ultrasound guidance. T1-weighted FLASH and spin-echo sequences were used to monitor the procedure. Enhanced CT was performed at 24 h to assess thermal necrosis. FLASH imaging showed an enlarging area of signal change during ILP. The final extent of this correlated closely with the extent of tissue necrosis on CT. Spin-echo imaging was disappointing because of poor contrast between the treated tissue and normal liver/untreated tumour. Per-procedural MR imaging accurately and reliably depicts ILP-induced necrosis. MR control may permit more widespread application of ILP to the treatment of hepatic tumours.

We undertook a phase I dose-escalation study of verteporfin photodynamic therapy (PDT) in 15 patients with locally advanced pancreatic cancer. Needle placement and laser delivery were technically successful in all patients. Thirteen patients were treated with a single laser fibre. Three treatments were carried out each at 5, 10 and 20 J/cm2; and 5 treatments (4 patients) at 40 J/cm2. A further 2 patients were treated with 2 or 3 laser fibres at 40 J/cm2. Tumour necrosis was measured on CT (computed tomography) by two radiologists 5 days after treatment. There was a clear dosedependent increase in necrosis with a median area of 20 x 16 mm (range 18 x 16 to 35 x 30 mm) at 40 J/cm2. In the 2 patients treated with multiple fibres, necrosis was 40 x 36 mm and 30 x 28 mm, respectively. There were no early complications in patients treated with a single fibre. Both patients treated with multiple fibres had evidence on CT of inflammatory change occurring anterior to the pancreas but without clinical deterioration. These results suggest that single fibre verteporfin PDT is safe in a clinical setting up to 40J/cm2 and produces a dose-dependent area of pancreatic necrosis.

BACKGROUND: Palliation of malignant dysphagia is possible by a variety of methods although all have significant drawbacks. Laser therapy is an effective and safe treatment but has to be repeated at four to five weekly intervals to maintain palliation. A means of augmenting the benefits while reducing the need for repeat treatments would be highly beneficial to these patients. AIMS: To prospectively explore the safety and efficacy of intraluminal radiotherapy (brachytherapy) when used to augment laser recanalisation for malignant dysphagia. PATIENTS: Nineteen patients with dysphagia due to advanced adenocarcinoma of the oesophagus or cardia were recruited. METHODS: All patients received laser recanalisation until able to swallow a soft diet or better, before the application of a single dose of brachytherapy (10 Gy at 1 cm from the source). Patients were followed up and treated promptly by further endoscopic means in the event of their dysphagia worsening. RESULTS: Six patients (32%) required no further treatment until death at a median of 10 weeks (range 1-20 weeks). Further therapy was required at a median of 11 weeks (range 4-37 weeks) after brachytherapy for those 13 patients with recurrent dysphagia. Subsequent symptom control required endoscopic intervention at an average of once every nine weeks. There was no mortality associated with laser or brachytherapy. Median survival from initial treatment and including the one survivor was 36 weeks (range 5-132 weeks). CONCLUSIONS: Laser plus brachytherapy offers a safe and effective means of palliating malignant dysphagia due to adenocarcinoma, with a longer dysphagia free interval than historical controls treated with laser alone.

Photodynamic therapy (PDT) has the potential to destroy small tumours with safe healing of adjacent normal tissue. This study looks at the effects of PDT on the normal pancreas and adjacent tissues in hamsters using the photosensitiser meso-tetrahydroxyphenylchlorin (mTHPC). Pharmacokinetic studies used fluorescence microscopy on sections of pancreas, stomach and duodenum 1 h to 6 days after mTHPC. Highest levels of sensitiser were seen in the gastric and duodenal mucosa and in the acinar pancreas after 2-4 days. For PDT, light at 652 nm was delivered by placing a 0.2 mm diameter bare-ended fibre against the tissue. An energy of 50 J was used 2 or 4 days after 0.1 or 0.3 mg kg-1 mTHPC and animals killed 1 to 7 days later. Maximum necrosis was seen 3 days after PDT with lesions up to 4 mm in pancreas, 4.5 mm in duodenum and 2.5 mm in stomach. By fractionating the light dose, the lesion size could be increased by 30%. The main complication was free or sealed duodenal perforation (avoided by shielding the duodenum). Partial, reversible bile duct obstruction was seen occasionally. There was no macroscopic damage to the bile ducts or major blood vessels. Apart from the duodenum, all lesions healed safely. In this animal model, only the duodenum was at risk of serious, irreversible damage. Treatment is likely to be safer in the much thicker human duodenum. mTHPC is a powerful photosensitiser and suitable for further study for tumours in the region of the pancreas although care is required near the duodenum. Images Figure 5 Figure 6

Purpose: Photodynamic therapy (PDT) has considerable potential for the treatment of superficial bladder neoplasia. Problems of detrusor muscle scarring and prolonged cutaneous photosensitivity with current photosensitizers may be reduced by using the new photosensitizer precursor, 5-aminolevulinic acid (ALA). We studied the fluorescence distribution of protoporphyrin IX (PpIX, the active derivative of ALA) in rat urinary bladder after intravesical administration of ALA as the first step to undertaking PDT using locally administered ALA.Materials and Methods: Solutions of varying concentrations of ALA and pH were given intravesically to Wistar rats. The bladder was removed 1 to 24 hours later for measurement of the tissue levels of PpIX by fluorescence microscopy in the layers of the bladder wall.Results: The stability of the ALA solution steadily decreased as the pH was increased from 2.1 to 7. The best value was pH 5.5, at which the stability of the solution and the urothelial tolerance were both...

Photodynamic therapy (PDT) using 5-aminolaevulinic-acid-(ALA)-induced protoporphyrin IX (PPIX) increases survival in hamsters with pancreatic cancer. However, experiments with other photosensitizers on this model show a high risk of duodenal perforation. In this paper, the pharmacokinetics and PDT effects of ALA on normal tissues in the pancreatobiliary region are presented. Using quantitative fluorescence microscopy, maximum PPIX fluorescence was seen in the bile ducts, less in the duodenal mucosa and least in the muscularis propria and pancreas. For PDT, light was delivered either using a bare fibre touching the tissue (single-point illumination), or irradiating a 1.5 cm diameter circular area. Single-point PDT (50 J) produced only localized reversible damage without perforation. Surface irradiation of the whole periampullary region (50 J cm−2) caused extensive damage, sometimes with perforation. Before PDT can be used safely to treat tumours of the pancreas and bile duct, further studies are necessary to understand its effect on larger areas of normal tissue.

Attempts to develop PDT for eradication of Helicobacter infection have only been successful in vitro. We have investigated the effect of topical sensitization (except ALA) of Helicobacter mustelae on explanted ferret gastric mucosa using one of five sensitizers (methylene blue (MB), toluidine blue O (TBO), phthalocyanine, haematoporphyrin derivative and 5-aminolavulinic acid), followed by irradiation with an appropriately tuned copper vapour pumped dye laser. A 90% reduction in counts of bacteria sensitized with 0.75 mg TBO kg −1 were seen after irradiation with 200 J cm −2 . Concentrations of MB of 0.75 mg kg −1 and 7.5 mg kg −1 were not toxic to H. mustelae , but the further addition of 20 J cm −2 laser light reduced colony counts by more than 99%. MB at a concentration of 75 mg kg −1 exhibited significant dark toxicity towards H. mustelae , but further addition of 20 J cm −2 laser light resulted in near eradication of all colonies. The remaining three compounds were ineffective. Finally, we studied the microscopic fluorescence distribution of MB (7.5 mg kg −1 ) on ferret gastric mucosa after topical administration. Fluorescence was greatest in the superficial mucosal layer, upon which lies the bacteria. However, from experiments on rats, the energy required to kill the sensitized bacteria was insufficient to damage the underlying mucosa. We conclude that Helicobacter can be killed on host mucosal epithelium following topical administration of MB and subsequent exposure to laser light.

Magnetic resonance imaging (MRI) is showing considerable promise as a monitor for interventional procedures. Laser surgery is “MRI compatible, ” and temperature-sensitive imaging techniques can be usefully applied to these procedures. We have been investigatingT1derived temperature-dependent imaging as a monitor for interstitial laser photocoagulation (ILP) in rat liver.In vitro experiments suggested that temperature calibration may be achieved. We have investigated ILPin vivo using short TR spin-echo imaging sequences taking one set of images every 30 s during and after the procedure. Our resultsin vivo suggest that this simple model may be inadequate for temperature mapping as the biological reaction to the ILP is on a similar time scale to that of the procedure. Nonetheless, MRI shows well-defined, repeatable signal changes that can be related to histological borders.

Experimental studies have been carried out using 5-aminolaevulinic acid (ALA) to induce transient porphyrin photosensitisation for photodynamic therapy (PDT) in a pancreatic cancer model in Syrian golden hamsters. ALA was given either intravenously or orally (in bolus or fractionated doses) with the laser light delivered by means of a bare fibre touching the tissue surface or external irradiation using a light-integrating cylindrical applicator. Animals were killed 1-24 h after ALA administration for pharmacokinetic studies and 3-7 days after light exposure to study PDT-induced necrosis. A separate survival study was also performed after a fractionated oral dose of ALA and external irradiation. Protoporphyrin IX sensitisation in the tumour tissue as measured by quantitative fluorescence microscopy was highest after intravenous administration of 200 mg kg-1 ALA and then in decreasing order after oral fractionated and oral bolus doses (both 400 mg kg-1). Laser light application at 630 nm to give 12-50 J from the bare fibre or 50 J cm-2 using surface illumination with the cylindrical applicator resulted in tumour necrosis up to 8 mm in depth. In larger tumours a rim of viable tumour was observed on the side opposite to illumination. In a randomised study, survival of treated animals was significantly longer than in the untreated control group (log-rank test, P < 0.02), although all animals died of recurrent tumour. This technique shows promise in the treatment of small volumes of tumour in the pancreas. Images Figure 2 Figure 3 Figure 4

The diagnosis and treatment of pancreaticobiliary malignancy is of major interest to our group. Building on prior work, we undertook a phase I study of verteporfin photodynamic therapy in patients with locally advanced, unresectable, pancreatic cancer. We also initiated an optical diagnostic study using elastic scattering spectroscopy (ESS) of the normal-appearing periampullary duodenal mucosa in vivo to investigate the hypothesis of a field effect in pancreaticobiliary malignancy. In a phase I dose escalation study, patients were treated with interstitial verteporfin PDT via a single fibre, to determine its general safety profile and the optimum treatment parameters needed to achieve effective and safe necrosis of tumour, With increasing light doses, there was a linear increase in the extent of tumour necrosis around the fibre, without serious adverse events. Follow-on studies using multiple fibres are planned. In 30 patients with benign or malignant pancreaticobiliary disease undergoing clinically-indicated endoscopy, ESS spectra were collected from the normal-appearing duodenum and antrum and a diagnostic algorithm generated by principle component and linear discriminant analysis. Pooled data from duodenal sites distal to the ampulla gave a sensitivity of 86% and a specificity of 72% (82% AUC) for the detection of malignancy, whereas those from the periampullary region had a sensitivity of 77% and a specificity of 61% (72% AUC); antral measurements were not able to discriminate with such accuracy. These early results suggest that ESS of the duodenal mucosa could represent a novel minimally invasive diagnostic test for pancreaticobiliary malignancy.

The management of patients with ’field cancerization‘ of the oral mucosa, with multicentric foci of invasion, presents a considerable problem for the head and neck surgeon. Surgical resection of synchronous or metachronous primary squamous cell carcinomas, along with adjacent premalignant lesions, is likely to be associated with considerable mutilation. Photodynamic therapy (PDT) has been shown to be of value in the treatment of superficial tumours in the upper aerodigestive tract, with excellent healing of treated areas. This study reports the use of PDT to treat 11 patients with ’field cancerization‘ occurring in the oral cavity. Six patients had multiple primary cancers and five had single primary tumours. All had associated areas of leukoplakia. Each received Photofrin 2 mg/kg 48 hours prior to photoirradiation with 50–100 J/cm² red laser light by surface illumination. Six to eight weeks later treated areas in 10 of the 11 patients showed a complete response to PDT; one patient had areas of residual leukoplakia. Two patients developed further areas of leukoplakia or erythroplakia within 12 months but no patient has had evidence of recurrent invasive carcinoma in the treated areas. Longer term follow-up will be necessary to exclude further recurrence. It is concluded that PDT offers an effective repeatable treatment option, whether on its own or as an adjunct to local excision, for patients with ’field cancerization‘ of the oral cavity.

Laser palliation for advanced rectal or rectosigmoid cancer requires repeat treatments every four to six weeks. Thirteen patients (seven men, six women) age range 65-91 (median 81) received additional external beam radiotherapy in an attempt to reduce the frequency of laser treatments required. After successful laser recanalisation, patients were treated with a dose of 30-55 Gy in 10-20 fractions. Bowel symptoms were well controlled for prolonged periods in 11 patients (85%) and further laser procedures were only required every 19 weeks median (range 6-53 weeks). The laser energy required after radiotherapy was only 800 J/month (median). Survival was 14 months (median, range 2.5-20 months) for the seven patients who have died. Seven patients received laser treatment only for three months or more (median 14 weeks, range 13-39). In this group control of symptoms required procedures every four weeks (median) before radiotherapy and 20 weeks (median) afterwards. The laser energy required before radiotherapy was 15,000 J/month and 2000 J/month afterwards (Wilcoxon rank sum test, p < 0.01 for both). Radiotherapy was well tolerated in all but one patient. Three patients developed strictures after radiotherapy but all were dealt with endoscopically. There were no complications solely due to endoscopic procedures. Additional radiotherapy enhances laser palliation for inoperable rectal or rectosigmoid cancer.

Interstitial laser photocoagulation (ILP) is a new percutaneous technique of thermal destruction (necrosis) of deep-seated tumours, using low power laser energy. Our purpose was to investigate: (i) the effects of different laser wavelengths on the extent of thermal damage produced; and (ii) the role of charring around the fibre tip during ILP. Forty-five normal Wistar rats (250–300 g) had ILP to their liver (exposed at laparotomy) by inserting a 400 μm optical fibre into the liver, and activating the laser at 1, 2 or 3W. This was performed at three laser wavelengths (1064 nm Nd-YAG, 1320 nm Nd-YAG, 805 nm diode) using a clean plane-cleaved fibre, and at two wavelengths (1064 nm and 1320 nm Nd-YAG) using a fibre with pre-charring at its tip. The 805 nm and 1320 nm laser wavelengths produced significantly greater necrosis than the 1064 nm, using a clean fibre tip (mean diameters at 2 W were 21.7 mm, 18.3 mm, 8 mm respectively). Pre-charring the fibre significantly increased the necrotic lesion size at 1064 nm (mean diameter at 2 W was 14.7 mm). Using more strongly absorbed wavelengths (805 nm and 1320 nm) and pre-charring the fibre tip give greater thermal damage during ILP, contrary to previously held views that the optimal wavelength for ILP was 1064 nm in the absence of charring.

Fifty-five liver metastases in 21 patients were treated with interstitial laser photocoagulation (ILP). Tumors were irradiated with a neodymium yttrium aluminum garnet laser via optical fibers passed through 19-gauge needles inserted under ultrasound (US) guidance. Heating of the tumor was evident at real-time US as an expanding and coalescing echogenic zone around the needle tips. After ILP, dynamic computed tomography (CT) showed laser-induced necrosis as a new area of nonenhancement. Necrosis of tumor volume was more than 50% in 82% (45 of 55) of the tumors, and 100% necrosis was achieved in 38% (21 of 55). Metastases smaller than 4 cm in diameter were treated more effectively and required fewer treatment sessions than did those larger than 4 cm. Complications were minor and included severe pain in four cases, persistent pain for up to 10 days in 11 cases, and asymptomatic subcapsular hematoma (four cases) and pleural effusion (six cases) seen with CT. ILP is safe and effective for liver tumor destruction, and US and CT are useful in different aspects of treatment monitoring.

Forty one patients with bleeding vascular ectasias of the upper gastrointestinal tract who required blood transfusion were treated with endoscopic Nd:YAG laser photocoagulation and followed for 34 months (median). Four distinct groups of patients were identified. There was a sustained reduction in transfusion requirements after laser treatment in all those with single (nine patients) and multiple (seven patients) angiodysplasia, in 12 of 16 (75%) patients with watermelon stomachs, and in six of nine (66%) patients with hereditary haemorrhagic telangiectasia. Overall, 25 patients (61%) required minimal or no transfusion after treatment and nine (22%) whose bleeding was controlled initially, later developed recurrent bleeding which was controlled with further laser (total 34 of 41, 83%). Surgery succeeded in a further three patients (7%) in whom laser had failed (in one case possibly because of laser induced haemorrhage). Five more cases of possible laser induced haemorrhage resolved with conservative treatment. One patient sustained a treatment related perforation and died: one patient with cirrhosis died of encephalopathy within one month of starting laser treatment. In two patients transfusion requirements were unchanged despite laser. Nd:YAG laser is a safe and effective treatment for most patients with upper gastrointestinal angiodysplasia.

Endogenously synthesised protoporphyrin IX (PpIX) following the administration of 5-amino-laevulinic acid (ALA) is an effective photosensitiser for photodynamic therapy (PDT). Following intravenous administration, PpIX accumulates predominantly in mucosa of hollow viscera and on light exposure, mucosal ablation results with relative sparing of the submucosa and muscularis layers. Oral administration is effective with ALA in contrast to conventional exogenous photosensitisers such as haematoporphyrin derivative and phthalocyanines. Oral administration of ALA is also simpler, safer, cheaper and more acceptable to patients. We studied the porphyrin sensitisation kinetics profile in the stomach, colon and bladder in normal rats following enterally and parenterally administered ALA using microscopic fluorescence photometric studies of frozen tissue sections. Mucosal cells in all three organs exhibit higher fluorescence levels as compared with underlying smooth muscle following both intravenous and oral administration. Peak concentration were seen 4 h after sensitisation at the highest doses used (200 mg kg-1 i.v., 400 mg kg-1 oral), and slightly earlier with lower doses. The temporal kinetics of both routes of administration were similar although a higher oral dose was required to achieve the same tissue concentration of PpIX. The highest level of fluorescence was achieved in the gastric mucosa and in decreasing levels, colonic and bladder mucosa. A similar degree of mucosal selectivity was achieved in each organ with each route of administration but an oral dose in excess of 40 mg kg-1 was required to achieve measurable PpIX sensitisation. In a pilot clinical study, two patients with inoperable rectal adenocarcinomas were given 30 mg kg-1 and one patient with sigmoid colon carcinoma was given 60 mg kg-1 ALA orally. Serial biopsies of normal and tumour areas were taken over the subsequent 24 h. Fluorescence microscopy of these specimens showed maximum accumulation of PpIX 4 to 6 h after administration of 30 mg kg-1 ALA. There was greater PpIX accumulation in tumour than adjacent normal mucosa in two patients. Preferential PpIX accumulation in tumour was greater in the patient receiving 60 mg kg-1 ALA. Images Figure 2 Figure 10

Background Intraoperative diagnosis of sentinel node metastases enables an immediate decision to proceed to axillary lymph node dissection, avoiding a second operation in node-positive women with breast cancer. Methods An optical scanner was developed that interrogated the cut surface of bivalved, but otherwise unprocessed, sentinel lymph nodes with pulses of white light by elastic scattering spectroscopy (ESS). The scattered light underwent spectral analysis, and individual spectra were initially correlated with conventional histology to develop a diagnostic algorithm. This algorithm was used to create false colour-coded maps of scans from an independent set of nodes, and the optimal criteria for discriminating between normal and cancer spectra were defined statistically. Results The discriminant algorithm was developed from a training set of 2989 spectra obtained from 30 metastatic and 331 normal nodes. Subsequent scans from 129 independent nodes were analysed. The scanner detected macrometastases (larger than 2 mm) with a sensitivity of 76 per cent (69 per cent including micrometastases) and specificity of 96 per cent. Conclusion In this proof-of-principle study, the ESS results were comparable with current intraoperative diagnostic techniques of lymph node assessment.

Pancreatic adenocarcinoma ranks as the fourth most common cause of cancer death in the USA. Patients usually present late with advanced disease, limiting attempted curative surgery to 10% of cases. Overall prognosis is poor with one-year survival rates of less than 10% with palliative chemotherapy and/or radiotherapy. Given these dismal results, a minimally invasive treatment capable of local destruction of tumor tissue with low morbidity may have a place in the treatment of this disease. In this paper we review the preclinical photodynamic therapy (PDT) studies which have shown that it is possible to achieve a zone of necrosis in normal pancreas and implanted tumour tissue. Side effects of treatment and evidence of a potential survival advantage are discussed. We describe the only published clinical study of pancreatic interstitial PDT, which was carried out by our group (Bown et al Gut 2002), in 16 patients with unresectable locally advanced pancreatic adenocarcinoma. All patients had evidence of tumor necrosis on follow-up imaging, with a median survival from diagnosis of 12.5 months. Finally, we outline a phase I dose-escalation study of verteporfin single fibre PDT followed by standard gemcitabine chemotherapy which our group is currently undertaking in patients with locally advanced pancreatic cancer. Randomized controlled studies are also planned.

The effect of combining photodynamic therapy (PDT) and bioreductive drugs has been investigated using the RIF-1 experimental murine tumour. Light was delivered interstially to the tumour at 675 nm using a single optical fibre attached to an argon-ion dye laser. The photosensitizer was disulphonated aluminium phthalocyanine (AlS2Pc) and the bioreductive drugs were the dual function nitroimidazole RSU1069 and its pro-drug RB6145. Varying the time between administration of the photosensitizer and light delivery (TL) from 30 min to 24 h had little influence on the extent of the anti-tumour effect of PDT alone, as measured by the regrowth delay endpoint. When the bioreductive drug was included in the treatment, administered 20 min before light irradiation, regrowth delay was greatly increased. The effectiveness of the combined treatment was optimum for short values of TL (about 1 h). Fluorescence microscopy was used to investigate the distribution of the photosensitizer within the tumours. This showed that the compound was mainly confined to the tumour vasculature over the first few hours post-treatment. The high efficacy of the combined treatment of PDT and bioreductive drugs for short values of TL suggest that photodynamic action, during the period when the photosensitizer AlS2Pc is confined to the vasculature, enhances the severity of tumour hypoxia which is sufficient to induce activation of the bioreductive drugs. Images Figure 1

The palliative management of hepatic metastases remains unsatisfactory. There is a need for a simple non invasive technique which can stop or retard the rate of tumour growth. In principle, Interstitial Laser hyperthermia may fulfil such a role. In experimental studies, this technique produced precise in situ necrosis within solid organs which healed safely. In a pilot feasibility study, we treated ten patients with a total of 18 hepatic metastases on 31 occasions using a percutaneous approach to achieve an overall objective response rate of 44%. The treatment proved simple to perform, was well tolerated and produced radiological evidence of necrosis in small metastases (diameter less than or equal to 3 cm). However, further research is required before the technique can be regarded as established. Its future role in most cases will be to control the growth of discrete hepatic metastases unsuitable for resection. In instances where the extent of necrosis can be matched accurately to tumour volume, the potential for cure exists. Images Figure 1 Figure 2 Figure 3

Photodynamic therapy (PDT) is often thought to be able to effect selective tumour necrosis. This therapeutic selectivity, based on transient diferences in tumour: normal tissue photosensitizer concentration ratios, is rarely useful clinically in extracranial tumours, although PDT itself may be of value by virtue of the nature of the damage produced and healing of normal tissue by regeneration. This report describes the effects of PDT on normal pancreas and chemically induced pancreatic cancers in the hamster, where a diferent mechanism of selective necrosis may be seen. Photosensitizer distribution in normal and neoplastic pancreas was studied by chemical extraction and fluorescence microscopy. Correlation of distribution studies with necrosis produced by PDT shows that the photodynamic dose (product of tissue concentration of sensitizer and light dose) threshold for damage is seven times as high for normal pancreas as for pancreatic cancer. Tumour necrosis extended to the point where tumour was invading normal areas without damaging the normal tissue. In rat colonic cancer, photodynamic dose thresholds in tumour and normal tissue are similar and so such marked selectivity of necrosis is not possible. The reason for this selectivity in the pancreas is not clear, but recent evidence has suggested a diference in response to PDT between normal and neoplastic pancreatic cell lines and the presence of a singlet oxygen scavenger in normal pancreas is postulated. Furthermore, the present fluorescence microscopy studies suggest that tumour stroma contains the highest level of photosensitizer and thus receives the highest photodynamic dose during PDT. These results suggest a possible role for PDT in treating small pancreatic tumours or as an adjuvant to other techniques, such as surgery, that reduce the main bulk of tumours localized to the pancreas.

Multiple four-fibre low-power interstitial laser hyperthermia was performed in the canine liver to establish the parameters with which large areas of thermal necrosis could be made. Using 1.5 W for 670s (4020 J in total) and a fibre spacing of 1.5 cm, lesions with dimensions of 3.6 × 3.1 × 2.8 cm were achieved in 75 per cent of those attempted. There was no mortality and a low morbidity rate. These lesions could be visualized in both their development and resolution using ultrasonography. Healing occurred by 1 year. Temperatures in the centre of the heated region were 60°C, which is more than enough to cause thermal cell death. There was good correlation between the temperatures recorded, the sonographic changes seen, and the pathological evidence of necrosis. Multiple-fibre low-power interstitial laser hyperthermia performed with ultrasonic guidance may be of use in the treatment of liver tumours.

Dysplasia in the upper gastrointestinal tract carries a risk of invasive malignant change. Surgical excision of the affected organ is the only treatment available. Photodynamic therapy has been shown to be promising in the treatment of early and superficial tumours and may be useful for the ablation of dysplastic mucosa. Because of the diffuse nature of the disease, such treatment would necessarily involve destruction of large areas of mucosa and it is desirable to confine its effect to the mucosa in order that safe healing can take place. By means of photometric fluorescence microscopy, we have studied the pattern of photosensitisation in the normal rat stomach using di-sulphonated aluminium phthalocyanine (AlS2Pc) and 5-aminolaevulinic acid (ALA) as photosensitisizers. AlS2Pc resulted in a panmural photosensitisation of the gastric wall with the highest level encountered in the submucosa. The mucosa and muscularis propria were sensitised to equal extent. Following light exposure, a full thickness damage resulted. ALA is a natural porphyrin precursor and exogenous administration gave rise to accumulation of protoporphyrin IX (PPIX) in the cells. The resultant pattern of photosensitisation was predominantly mucosal and its photodynamic effect was essentially confined to the mucosa. ALA produced a selective photosensitisation of the gastric mucosa for its photodynamic ablation with sparing the underlying tissue layers. Images Figure 3 Figure 4 Figure 5 Figure 9

Photodynamic therapy (PDT) is an anti-cancer treatment which involves the systemic administration of a photosensitising drug which is preferentially absorbed by tumour tissue. Relatively little drug should be absorbed by the surrounding normal tissues. Tumour destruction is achieved when the tumour is illuminated with light of a wavelength which activates the photosensitising drug thereby inducing a cytotoxic reaction. However studies in many tissues have shown that the hoped for tumour selectivity is rarely achieved. Using the rabbit mandible and gingiva as our models we have studied the effects of various doses of PDT on the tissues of the oral cavity, namely mucosa, bone, muscle and salivary gland. The photosensitiser used was di-sulphonated aluminium phthalocyanine. Results show that whereas bone is extremely resistant to PDT the other tissues are vulnerable to it. In the case of muscle and salivary gland this susceptibility is very much dose related. In salivary tissue necrotising sialometaplasia was observed in areas of the gland adjacent to those that had undergone necrosis. All tissues were noted to heal or regenerate well following PDT injury. Images Figure 2 Figure 3 Figure 5 Figure 6