DCE-MRI biomarkers of tumour heterogeneity predict CRC liver metastasis shrinkage following bevacizumab and FOLFOX-6.

BACKGROUND: There is limited evidence that imaging biomarkers can predict subsequent response to therapy. Such prognostic and/or predictive biomarkers would facilitate development of personalised medicine. We hypothesised that pre-treatment measurement of the heterogeneity of tumour vascular enhancement could predict clinical outcome following combination anti-angiogenic and cytotoxic chemotherapy in colorectal cancer (CRC) liver metastases. METHODS: Ten patients with 26 CRC liver metastases had two dynamic contrast-enhanced MRI (DCE-MRI) examinations before starting first-line bevacizumab and FOLFOX-6. Pre-treatment biomarkers of tumour microvasculature were computed and a regression analysis was performed against the post-treatment change in tumour volume after five cycles of therapy. The ability of the resulting linear model to predict tumour shrinkage was evaluated using leave-one-out validation. Robustness to inter-visit variation was investigated using data from a second baseline scan. RESULTS: In all, 86% of the variance in post-treatment tumour shrinkage was explained by the median extravascular extracellular volume (v(e)), tumour enhancing fraction (E(F)), and microvascular uniformity (assessed with the fractal measure box dimension, d(0)) (R(2)=0.86, P<0.00005). Other variables, including baseline volume were not statistically significant. Median prediction error was 12%. Equivalent results were obtained from the second scan. CONCLUSION: Traditional image analyses may over-simplify tumour biology. Measuring microvascular heterogeneity may yield important prognostic and/or predictive biomarkers.

Cross-visit tumor sub-segmentation and registration with outlier rejection for dynamic contrast-enhanced MRI time series data.

Clinical trials of anti-angiogenic and vascular-disrupting agents often use biomarkers derived from DCE-MRI, typically reporting whole-tumor summary statistics and so overlooking spatial parameter variations caused by tissue heterogeneity. We present a data-driven segmentation method comprising tracer-kinetic model-driven registration for motion correction, conversion from MR signal intensity to contrast agent concentration for cross-visit normalization, iterative principal components analysis for imputation of missing data and dimensionality reduction, and statistical outlier detection using the minimum covariance determinant to obtain a robust Mahalanobis distance. After applying these techniques we cluster in the principal components space using k-means. We present results from a clinical trial of a VEGF inhibitor, using time-series data selected because of problems due to motion and outlier time series. We obtained spatially-contiguous clusters that map to regions with distinct microvascular characteristics. This methodology has the potential to uncover localized effects in trials using DCE-MRI-based biomarkers.

Identification of early predictive imaging biomarkers and their relationship to serological angiogenic markers in patients with ovarian cancer with residual disease following cytotoxic therapy.

BACKGROUND: Patients with recurrent ovarian cancer often achieve partial response following chemotherapy, resulting in persistent small volume disease. After completion of treatment, the dilemma of when to initiate subsequent chemotherapy arises. Identification of biomarkers that could be used to predict when subsequent treatment is needed would be of significant benefit. DESIGN: Twenty-three patients with advanced ovarian cancer and residual asymptomatic disease following chemotherapy underwent dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) at study entry, 4, 8, 12, 18 and 26 weeks or disease progression. A subgroup of patients provided plasma samples within which a panel of angiogenic biomarkers was quantified. RESULTS: By 4 weeks, significant differences in whole tumour volume, enhancing fraction and Ca125 were observed between patients whose disease progressed by 26 weeks and those who remained stable. Significant correlations between plasma soluble vascular endothelial growth factor receptor-1 (sVEGFR-1) and sVEGFR-2 concentrations, and blood volume and tumour endothelial permeability surface area product measured by DCE-MRI were observed. CONCLUSIONS: Imaging markers have a potential role in early prediction of disease progression in patients with residual ovarian cancer and may supplement current measures of progression. The correlation of DCE-MRI and serological biomarkers suggests that tumour angiogenesis affects these markers through common biological means and warrants further investigation.

Enhancing fraction in glioma and its relationship to the tumoral vascular microenvironment: A dynamic contrast-enhanced MR imaging study.

BACKGROUND AND PURPOSE: EnF is a newly described measure of proportional tumor enhancement derived from DCE-MR imaging. The aim of this study was to assess the relationship between EnF and the more established DCE-MR imaging parameters: K(trans), v(e), and v(p). MATERIALS AND METHODS: Forty-two patients with 43 gliomas (16 grade II, 3 grade III, and 24 grade IV) were studied. Imaging included pre- and postcontrast T1-weighted sequences through the lesion and T1-weighted DCE-MR imaging. Parametric maps of EnF, K(trans), v(e), and v(p) were generated. Voxels were classified as enhancing if the IAUC was positive (EnF(IAUC)(60>0)). A threshold of IAUC > 2.5 mmol.s was used to generate EnF(IAUC)(60>2.5). Both measures of EnF were compared with the DCE-MR imaging parameters (K(trans), v(e), and v(p)). RESULTS: In grade II gliomas, EnF(IAUC60>0) and EnF(IAUC60>2.5) correlated with v(p) (R(2) = 0.6245, P < .0005; and R(2) = 0.4727, P = .003) but not with K(trans) or v(e). In grade IV tumors, both EnF(IAUC60>0) and EnF(IAUC60>2.5) correlated with K(trans) (R(2) = 0.3501, P = .001; and R(2) = 0.4699, P < .0005) and v(p) (R(2) = 0.1564, P = .01; and R(2) = 0.2429, P = .007), but not with v(e). Multiple regression analysis showed K(trans) as the only independent correlate of both EnF(IAUC60>0) and EnF(IAUC60>2.5) for grade IV tumors. CONCLUSIONS: This study suggests that in grade II tumors, EnF reflects v(p) and varies due to changes in vascular density. In grade IV gliomas, EnF is affected by K(trans) with secondary associated changes in v(p).

Phase I evaluation of CDP791, a PEGylated di-Fab' conjugate that binds vascular endothelial growth factor receptor 2.

PURPOSE: Specific blocking of vascular endothelial growth factor receptor 2 (VEGFR-2) is a novel therapeutic approach. Here, we report the first phase I clinical trial evaluation of CDP791, a PEGylated di-Fab' conjugate that binds VEGFR-2. EXPERIMENTAL DESIGN: Cohorts of patients received CDP791 at doses between 0.3 and 30 mg/kg every 3 weeks for the initial two doses. RESULTS: The compound was well tolerated with no dose-limiting toxicity. Dose-related hypertension was observed in patients receiving CDP791 10 mg/kg or more and several patients on the higher doses developed infusion-related cutaneous hemangiomata arising 28 to 106 days after the first drug administration and resolving 3 weeks after cessation. Biopsy and histologic evaluation showed that CDP791-bound VEGFR-2 is non-phosphorylated, suggesting that the drug is biologically active. Concentrations of CDP791 considered biologically relevant were sustained for 3 weeks when doses of 10 mg/kg or more were administered. Although no reductions in vascular permeability were recorded using dynamic contrast enhanced magnetic resonance imaging (DCE-MRI), there was a significant dose level-related reduction in tumor growth. While challenging the recent dogma that active VEGF inhibitors should modulate DCE-MRI measurements of vascular permeability, this highlights the potential of serial three-dimensional tumor measurements to detect tumor growth arrest. Twelve patients received drug for more than two treatments, although no partial or complete responses were seen. CONCLUSION: The data show that CDP791 is biologically active and well tolerated, achieving appropriate plasma concentrations when administered at 10 mg/kg or more every 3 weeks.

Quantifying heterogeneity in dynamic contrast-enhanced MRI parameter maps.

Simple summary statistics of Dynamic Contrast-Enhanced MRI (DCE-MRI) parameter maps (e.g. the median) neglect the spatial arrangement of parameters, which appears to carry important diagnostic and prognostic information. This paper describes novel statistics that are sensitive to both parameter values and their spatial arrangement. Binary objects are created from 3-D DCE-MRI parameter maps by "extruding" each voxel into a fourth dimension; the extrusion distance is proportional to the voxel's value. The following statistics are then computed on these 4-D binary objects: surface area, volume, surface area to volume ratio, and box counting (fractal) dimension. An experiment using 4 low and 5 high grade gliomas showed significant differences between the two grades for box counting dimension computed for extruded v(e) maps, surface area of extruded K(trans) and v(e) maps and the volume of extruded v(e) maps (all p < 0.05). An experiment using 18 liver metastases imaged before and after treatment with a vascular endothelial growth factor (VEGF) inhibitor showed significant differences for surface area to volume ratio computed for extruded K(trans) and v(e) maps (p = 0.0013 and p = 0.045 respectively).

Optimisation of illumination for photodynamic therapy with mTHPC on normal colon and a transplantable tumour in rats.

Recent reports suggest that the effect of photodynamic therapy (PDT) can be enhanced by fractionating the light dose or reducing the light fluence rate. We assessed these options on two tissues in rats (normal colon and a transplanted fibrosarcoma) using the photosensitiser meta-tetrahydroxyphenylchlorin (mTHPC). Animals were sensitised with 0.3 mg/kg mTHPC, 3 days prior to illumination with red light (652 nm) using a single fibre touching the target tissue and killed 1-3 days later for quantitative measurement of the extent of PDT necrosis. Results were similar for both tissues, although the differences between illumination regimens were less marked in tumour tissue. Using continuous illumination and a fixed low energy in colon, the extent of necrosis was up to almost three times larger with 5 mW than with 100 mW, although the maximum attainable necrosis was independent of power. The long treatment time using 5 mW could be halved without loss of effect by increasing the power during treatment. Dividing the light into two equal fractions at 100 mW increased the lesion size by up to 20% in colon (independent of the timing of the dark interval), but by only 10% in tumour and had no effect at 20 mW. Previous studies using 5-aminolaevulinic acid (ALA) showed a much larger effect of fractionation that was critically dependent on the timing of the dark interval. We postulate that enhancement of PDT by fractionation is due to improved oxygen supply to the treated area which may be due to reversal of temporary vascular occlusion (more likely with ALA) or less rapid photochemical consumption of oxygen (more likely with mTHPC). At lower fluence rates, the oxygen consumption rate is not fast enough to be improved by fractionation. We conclude that fractionated or low power light delivery can enhance PDT with mTHPC. Although the effects are not large, this may be of value for interstitial treatment of solid tumours when multiple sites are treated simultaneously.

Interstitial laser photocoagulation and interstitial photodynamic therapy of normal lung parenchyma in the pig.

Interstitial laser photocoagulation (ILP) and interstitial photodynamic therapy (PDT) involve delivery of light to lesions in solid organs using thin fibres passed through needles inserted percutaneously under image guidance. In ILP, the laser energy heats the tissue, whereas in PDT it activates a previously administered photosensitising agent. This study looks at their potential for treating localised, small, peripheral lung cancers in patients unsuitable for surgery. Experiments were undertaken on nine normal pigs, up to four fibres being inserted into the lung parenchyma percutaneously under X-ray guidance (ILP: 2-3 W, 1000 q/fibre, from 805 nm diode laser, PDT, 100-200 J/fibre from 652 nm diode laser at 50-100 W, 3 days after 0.15 mg/kg mTHPC). Animals were killed from 3 days to 3 months later and the treated areas examined macroscopically and microscopically. Both techniques were well tolerated, producing well-defined, localised lesions, typically 3.5 x 2 x 2 cm using four fibres. Histology showed thermal coagulative necrosis after ILP and haemorrhagic necrosis after PDT. Early small haematomas and late cavitation were sometimes seen after ILP, but not after PDT. PDT lesions healed with preservation of larger arteries and bronchi in the treated area. A few small pneumothoraces were seen which resolved spontaneously, probably related to the chest wall puncture. It was concluded that ILP and PDT lesions of a size large enough to cover a small tumour can be made safely in the lung parenchyma, although healing was better after PDT. Pilot clinical studies with both techniques are now justified on carefully selected patients.

Reduction in the response to coronary and iliac artery injury with photodynamic therapy using 5-aminolaevulinic acid.

OBJECTIVE: Photodynamic therapy (PDT) uses red light (non-thermal, non-ionising) to activate a previously administered photosensitizing drug. This inhibits neointimal hyperplasia in injured arteries in small animals where it appears safe and well tolerated. Our aim was to develop a method for percutaneous application of PDT to iliac and coronary arteries in a large animal model and investigate its influence on the remodeling and intimal hyperplastic response to balloon injury. METHODS: Studies were undertaken on 13 juvenile Large White-Landrace crossbred pigs (15-20 kg). After intravenous administration of the photosensitizing agent 5-amino laevulinic acid (ALA), the arterial tree was accessed via the left common carotid artery and balloon injuries made by over-distension in both common iliacs (thirteen animals) and one or two main coronary arteries (eight animals). Half the injured sites were then illuminated with red laser light transmitted via the catheter. Animals were culled 28 days later and tissue harvested for histomorphometry. RESULTS: Compared with control injured vessels, PDT treated, balloon injured coronary arteries had a larger lumen (1.4 vs. 0.8 mm2, P = 0.002), larger area within the external elastic lamina (2.8 vs. 2.2 mm2, P = 0.006) and smaller area of neointimal hyperplasia (0.4 vs. 0.7 mm2, P = 0.06), 28 days after intervention. Less neointimal hyperplasia and the absence of negative remodeling resulted in the lumen of PDT-treated, injured segments being the same as that of adjacent reference segments (1.5 vs. 1.6 mm2). Similar trends, but with smaller differences, were seen in the iliac vessels. CONCLUSIONS: Intra-arterial, trans-catheter PDT favourably influences the arterial response to balloon injury in both the coronary and peripheral circulations. This technique offers a promising new approach to restenosis after endovascular procedures.

Clinical study of adjuvant photodynamic therapy to reduce restenosis following femoral angioplasty.

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 follow- ing angioplasty. The data justify a randomized controlled trial.

Fine-needle interstitial photodynamic therapy of the lung parenchyma: photosensitizer distribution and morphologic effects of treatment.

STUDY OBJECTIVE: To look at the effect of interstitial photodynamic therapy (PDT) in normal lung parenchyma to assess its potential for treating localized, peripheral lung tumors. DESIGN: Studies were performed on normal Wistar rats using the photosensitizer meso-tetrahydroxyphenyl chlorine. Drug distribution was measured by fluorescence microscopy on tissue sections. Light was delivered to the lungs via a single fiber inserted percutaneously under x-ray control and the PDT effect studied in animals killed at times up to 6 months later. RESULTS: Fluorescence studies showed that the drug was initially distributed throughout the lung, but was later predominantly in the vasculature, bronchi, and macrophages. PDT produced sharply defined zones of hemorrhagic necrosis up to 12 mm in diameter that healed with regeneration of bronchial epithelium and local fibrosis. Different histologic effects were seen between drug light intervals of 1 and 3 days. Treatment was well tolerated, there was a low incidence of pneumothorax, and as long as the fiber tip was within the lung parenchyma, there was no damage to adjacent tissues. CONCLUSION: Interstitial PDT produces zones of necrosis in normal lung that heal safely by a percutaneous technique without affecting adjacent areas of untreated lung. If the lesion size can be increased by using multiple fibers, this could be a promising new technique for treating localized, peripheral lung cancers in patients who are unfit for surgery.

Intra-arterial photodynamic therapy using 5-ALA in a swine model.

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 micrograms) were photosensitised with 5-aminolaevulinic acid (5-ALA) induced protoporphyrin IX (PpIX) at a concentration of 120 mg/kg. Arterial biopsies were taken at intervals between 30 mins and 24 h 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 4 mm 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 6 h 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.

Interstitial laser photocoagulation of normal lung parenchyma in rats.

BACKGROUND: Management of peripheral lung tumours may be risky in patients with poor lung function or in the elderly. A new possibility is interstitial laser photocoagulation (ILP) in which tumours are gently coagulated using thin laser fibres placed percutaneously under radiological guidance. This could have a useful palliative role in selected patients, but to be safe the effects on normal lung parenchyma must first be understood. This paper describes the creation and healing of ILP lesions in the normal rat lung. METHODS: ILP was performed using single laser fibres placed percutaneously in the left lung of normal rats under general anaesthetic with radiological guidance (laser power 1-3 W at 805 nm, treatment time 250-1000 s). The lesion size and healing were studied in rats killed at times from three days to six months after treatment, the bursting pressure was measured, and any complications noted. RESULTS: Zones of necrosis up to 12 mm in diameter were produced, the size depending on the laser power and treatment time. Histological examination showed typical thermal effects with complete healing with fibrosis by two months. The effect was very localised with remarkably little effect on the structure and function of the rest of the lung. Adverse effects in the lung parenchyma only occurred if the ILP lesion involved the hilar vessels or the oesophagus, causing pulmonary congestion and perforation, respectively. Pneumothorax was seen in 6% of cases. CONCLUSIONS: ILP with a single fibre can produce a localised zone of necrosis in normal lung parenchyma which heals safely and which has little effect on the rest of the lung. Further study of this technique using multiple fibres in a larger animal model is warranted to see if it is feasible and safe to produce a large enough volume of necrosis to be of value in the treatment of small peripheral lung tumours in patients who are unsuitable for surgery or palliative radiotherapy.

Spatial measurement of oxygen levels during photodynamic therapy using time-resolved optical spectroscopy.

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.

Photodynamic therapy using mTHPC for malignant disease in the oral cavity.

Photodynamic therapy (PDT) produces local tumor necrosis, on activation of a previously administered sensitizer with non-thermal light of an appropriate wavelength. It is attractive for treating tumors of the mouth as tissue healing is particularly good. We describe the use of the photosensitizing agent meta tetrahydroxyphenyl chlorin (mTHPC, Foscan) for PDT of oral cancer, including patients with field cancerization. Nineteen patients with histologically confirmed oral cancer (8 with field change disease) and one with severe dysplasia, were sensitised with mTHPC intravenously. Activation was carried out 72-96 hr later with laser light at 652 nm using a range of light doses. The results were assessed clinically and histologically. Multiple biopsies were taken during the ulcerative stages to look at the effects of PDT and after healing to assess the overall treatment result. All single lesions up to stage T3 cleared after one PDT treatment (total of 6 patients). Three out of 6 T4 tumours were also cleared. Lesions in patients with field change disease did less well, only 9 of 14 T1 and T2s clearing, including 4 that required extra treatments with a higher light dose. Most healed very well, but tongue tethering was seen in 1 patient and another had necrosis in normal areas due to light scattering within the mouth. PDT using mTHPC is a promising new treatment for patients with oral cancer.

Interstitial photodynamic therapy in the canine prostate with disulfonated aluminum phthalocyanine and 5-aminolevulinic acid-induced protoporphyrin IX.

BACKGROUND: Photodynamic therapy (PDT) is an experimental approach for treating prostate cancer localized to the gland that does not involve surgery or irradiation. Second-generation photosensitizers 5-aminolevulinic acid (ALA) and aluminum disulfonated phthalocyanine (AlS2Pc) were studied in the normal canine prostate. METHODS: Tissue biodistribution of photosensitizers on serial biopsies was examined using fluorescence microscopy. Photodynamic therapy was done by delivering red light interstitially at 100 mW through fibers placed under transrectal ultrasound guidance. RESULTS: Peak levels of AlS2Pc appeared at 5-24 hr and at 3 hr for ALA. Macroscopic PDT lesions were up to 12 mm in diameter using AlS2Pc, but only 1-2 mm with ALA. Light at 300 mW caused thermal lesions. At 28 days, damaged glands remained atrophic, but the interlobular supporting stroma was well-preserved. Urethral lesions healed by 28 days without functional impairment. CONCLUSIONS: Although the results with ALA were disappointing, PDT using AlS2Pc looks like a promising modality for treatment of localized prostate cancer.

5-Aminolevulinic acid (ALA)-induced protoporphyrin IX fluorescence and photodynamic effects in the rat bladder: an in vivo study comparing oral and intravesical ALA administration.

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.

Photodynamic therapy using 5-aminolevulinic acid for premalignant and malignant lesions of the oral cavity.

BACKGROUND: Premalignant changes in the mouth, which are often widespread, are frequently excised or vaporized, whereas cancers are treated by excision or radiotherapy, both of which have cumulative morbidity. Photodynamic therapy (PDT) is another option that produces local tissue necrosis with light after prior administration of a photosensitizing agent. This heals with remarkably little scarring and no cumulative toxicity. This article describes the use of PDT with the photosensitizing agent 5-aminolevulinic acid (ALA) for premalignant and malignant lesions of the mouth. METHODS: Eighteen patients with histologically proven premalignant and malignant lesions of the mouth were sensitized with 60 mg/kg ALA by mouth and treated with laser light at 628 nanometers (100 or 200 Joules/cm2). The results were assessed macroscopically and microscopically. Biopsies were taken immediately prior to PDT for fluorescence studies, a few days after PDT to assess the depth of necrosis, when healing was complete, and up to 88 weeks later. RESULTS: The depth of necrosis varied from 0.1 to 1.3 mm, but complete epithelial necrosis was present in all cases. All 12 patients with dysplasia showed improvement (repeat biopsy was normal or less dysplastic) and the treated areas healed without scarring. Some benefit was observed in five of six patients with squamous cell carcinoma, but only two became tumor free (one with persistent mild dysplasia). No patient had cutaneous photosensitivity for longer than 2 days. CONCLUSIONS: PDT using ALA for dysplasia of the mouth produces consistent epithelial necrosis with excellent healing and is a simple and effective way to manage these patients. Results in invasive cancers are less satisfactory, mainly because the PDT effect is too superficial with current treatment regimens using ALA as the photosensitizing agent.

Laser therapy for breast cancer: MR imaging and histopathologic correlation.

PURPOSE: To investigate magnetic resonance (MR) imaging guidance of interstitial laser photocoagulation to treat primary breast cancer. MATERIALS AND METHODS: Twenty female patients with symptomatic breast cancers diagnosed at cytologic examination underwent interstitial laser photocoagulation by means of a single fiber prior to surgical excision. Gadolinium-enhanced T1-weighted three-dimensional fast low-angle shot (FLASH) MR imaging was performed before and after laser therapy (median, 48 hours; range, 24-96 hours). Following resection, tumors were mapped in detail histopathologically. The extent of disease, size of laser burn, and extent of residual tumor were correlated with MR findings. RESULTS: Twenty-seven tumors were detected at histopathologic examination in the 20 patients. Five patients had more than one invasive mass. Twenty-five of the 27 tumors were identified as discrete enhancing masses at MR. The two missed invasive foci were obscured on MR images by diffuse patchy enhancement that correlated with the presence of an associated extensive intraductal component. Early (4-hour) follow-up images failed to depict the laser effect. Later (24-96 hours) follow-up images depicted the laser-induced necrosis as a zone of nonenhancement within the residual enhancing tumor. The correlation coefficients (MR vs histopathologic analysis) for the laser-burn diameter and residual tumor were 0.80 and 0.86, respectively. CONCLUSION: Delayed gadolinium-enhanced MR images can help define the extent of laser-induced necrosis and residual tumor after interstitial laser photocoagulation therapy in breast cancer.

Interstitial and transurethral photodynamic therapy of the canine prostate using meso-tetra-(m-hydroxyphenyl) chlorin.

Photodynamic therapy (PDT) produces localised necrosis with light after prior administration of a photosensitising drug. Although the technique is promising for small tumours of hollow organs, little work has been done on solid organs like the prostate. We studied the tissue biodistribution and photodynamic effects of meso-tetra-(m-hydroxyphenyl) chlorin (mTHPC), a potent second-generation photosensitiser, on normal canine prostate in vivo. Using quantitative fluorescence microscopy, the highest concentration of mTHPC in the prostate was seen 24-72 hr after intravenous administration. For PDT, red light (650 nm) was delivered to the prostate by laser fibres inserted via the transurethral or transperineal route under transrectal ultrasound guidance. PDT lesions up to 40 mm in diameter (using 4 fibre sites) were produced, characterised by swelling, inflammatory response and extensive glandular destruction. There was persistent glandular atrophy at 90 days, but no disruption of the main stroma and no change in the ultimate size or shape of the gland. Urethral damage sometimes caused temporary urinary retention, but this resolved by 7 days, and no animal became incontinent. Occasional small lesions were seen in the rectum, but these healed without sequelae and there were no fistulae. Since cancer and normal prostate are likely to respond similarly, PDT has considerable promise for treating cancer confined to the gland as large areas of glandular tissue can be necrosed with safe healing. Because the structural integrity of the gland is maintained, PDT is unlikely to be of value in the management of benign prostatic hypertrophy.