Development of an alternative light source to lasers for photodynamic therapy: 2. Comparative in vivo tumour response characteristics

The performance of a low cost, table-top/portable light source was tested against an argon ion pumped dye laser for in vivo photodynamic therapy (PDT). The prototype delivers up to 1 W via a 4 mm flexible lightguide within a 30 nm bandwidth centred at any wavelength from 300 nm to 1200 nm at fluence rates of up to 8 W cm^–2. An in situ bioassay using regrowth delay of tumour T50/80 was used to quantify the relative efficacy of the prototype with a laser. The tumours were sensitized with haematoporphyrin derivative (HpD) and externally irradiated. There was no significant difference in the response of the tumour to treatment between the two light sources (p = 0.69). Mean growth delays ranged from 2 days (light dose 10 J cm^–2) to 20 days (light dose 100 J cm^–2). The estimate for the difference in means (laser minus prototype growth delay) was only 0.66 days and was not statistically significant. This in vivo study demonstrates that the prototype is equivalent to a laser in PDT effect. The device has low capital/running cost, is simple to use and is one of the most powerful, spectrally efficient non-laser PDT sources available.     

Thermal damage and haematoporphyrin-derivative-sensitized photochemical damage in laser irradiation of rabbit retina

In photodynamic therapy of solid tumours, 630 nm light is used to activate the photosensitizer haematoporphyrin derivative (HpD) in vivo, resulting in photochemical toxicity. This form of treatment has been used in a wide range of tumour types and sites, including ocular tumours such as malignant melanoma and retinoblastoma. In addition to HpD-sensitized photochemical effects, direct thermal damage may occur if the light exposure is sufficiently high. In this study, the thresholds for immediate and delayed thermal damage to the normal rabbit retina have been measured for a range of incident optical power and energy densities. HpD-sensitized photochemical damage has been demonstrated at light levels below these thermal thresholds. Thus, with appropriate selection of light power levels and exposure times, photodynamic response can be achieved without accompanying thermal damage.     

Photodynamic therapy in the management of malignant gliomas: a review

Interest in photodynamic therapy in the treatment of malignant gliomas began in the 1950s. Following the publication of papers showing that haematoporphyrin was excluded from the intact blood-brain barrier and that glioma cells grown in culture and subcutaneously could be killed by a combination of light and haematoporphyrin, a number of clinical trials was started, none of which has shown any measurable improvement in patient survival. The reason for this may relate to a lack of understanding of the mechanisms of photodynamic therapy and a lack of the scientific data needed to optimize photodynamic selectivity. This review discusses the potential role of photodynamic therapy in glioma treatment, and reviews the current clinical and experimental work in the field.     

Identification of brain tumours in rats using laser-induced fluorescence and haematoporphyrin derivative

Laser-induced fluorescence has been used for the identification of brain tumours in rats, which have been previously given tumour-seeking haematoporphyrin derivative. A pulsed nitrogen laser (=337 nm) was used in conjunction with an optical multichannel analyzer. For both inoculated RG-2 and TCVC rat-brain-tumour models, the blue autofluorescence was strongly reduced in the tumour compared with normal brain tissue, and at the same time the characteristic red-drug signal increased. The contrast between tumour and normal tissue was strongly enhanced by forming the ratio between the two signals. Implications for possible improvement of tumour delineation in brain tumour surgery are discussed.     

Scanning electron microscopic observations on photodynamic effects in cells in vitro

This paper reports an ultrastructural study of cell surfaces in normal (PTK₂) and malignant (Hela) cells in vitro using the scanning electron microscope. The study describes cells treated by haematoporphyrin derivatives (HPDs) from different sources as well as the destruction of cells which have taken up HPD in combination with laser microirradiation of single cells. The results indicate that an HPD effect on cell surface structure occurred: in general the microvilli were markedly reduced and some of the filopodia broken, shortened and thickened. The effects of different HPD drugs on cell surface structure differed to a certain extent within the limits of normal variation. In addition ultrastructural observations following HPD treatment plus laser microirradiation showed remarkable photodynamic cell damage identifiable within seconds after treatment.     

Fluorescence detection and photodynamic treatment of photosensitized tumours in special consideration of urology

Most methods of modern laser tumour therapy are physically based on the conversion of light to heat. Recently tumours have also been treated using ionizing processes for tissue ablation. Photodynamic laser therapy (PDT), however, involves light-induced non-thermal biochemical processes and the use of a photosensitizer.Several drugs are known to be stored selectively in tumours after systemic application. This transient marking can be used for diagnostic and therapeutic procedures. The marker most commonly used is dihaematoporphyrin ether/ester (DHE) intravenously injected at doses of 0.2–3.0 mg/kg bodyweight for diagnosis and therapy, respectively. The corresponding clearance intervals after injection of DHE range from 3–48 h to 25–75 h.Detection of photosensitized tumours might offer great advantages. The highly sensitive two-wavelength laser excitation method with computerized fluorescence imaging recently has been transferred to the hospital for clinical tests.Photoinduced production of singlet oxygen is claimed to be the initial process which leads to later tumour destruction and therapy. PDT has been applied to 20 patients suffering from superficial tumours (TIS GII–III) recurred after application of other treatments. The results after PDT were evaluated by three-monthly check-ups (endoscopy, cytology, bladder mapping, renal ultrasonography) as well as by computed tomography (CT) examination at 8–13 month intervals. In six patients treated by PDT no tumour recurrence has been found over the whole observation period of up to 5 years. Four patients have remained free of tumour (12 and 14 months) after repeated transurethral resection (TUR) and Nd-YAG laser therapy following PDT. Due to an initial application of insufficient irradiation four patients required a second PDT. In one patient a circumscribed dysplasia appeared at the left ostium 26 months following PDT and was treated successfully by means of thermal Nd-YAG laser irradiation following TUR. In six patients slight mucosal atypia persisted for a period of at least 2.5 years. One cystectomy had to be performed because of bladder shrinkage. The dissected bladder, however, was free of tumour.These preliminary results suggest that PDT is justified in patients who are in a worst-case situation with cystectomy recommended in case of recurrent superficial TIS bladder carcinoma and indicate the future potential of photodynamic therapy of tumours.Homogeneous irradiation of the area to be treated and a reliable light dosimetry are prerequisites for an effective tumour therapy. Standard instruments for a routine application do not exist, but are under development.     

光动力治疗裸小鼠胰腺移植癌的实验研究

目的 研究光动力治疗（ＰＤＴ）对胰腺癌的治疗效果,为胰腺癌寻找有效的治疗手段。方法 接种人胰腺癌细胞ＳＷ１９９０于裸小鼠皮下,建立移植癌模型,以血卟淋衍生物（ＨｐＤ）作为光敏剂,采用腹腔和瘤内局部注射两种不同方式给药,继以波长６３２．８ｎｍ的Ｈｅ－Ｎｅ激光照射肿瘤局部,观察光动力治疗后肿瘤的生长速度和组织形态学变化,并测定了肿瘤组织内脂质过氧化产物丙二醛（ＭＤＡ）的含量,对其治疗机制进行了初步探讨     

Behaviour of haematoporphyrin derivative in adenomas and adenocarcinomas of the colon: a microfluorometric study

Intravenously injected haematoporphyrin derivative localizes in malignant tissue more than it does in the surrounding normal tissues; this allows cancer to be treated photodynamically. The aim of this study is to determine whether adenomas of the large bowel, which are benign precarcinomatous lesions, accumulate HPD as well as does malignant tissue, and whether such accumulation occurs to a greater extent than it does in the surrounding normal mucosa. For this purpose, microspectrofluorometric analysis was performed on biopsy samples of adenomas, on adenocarcinomas, and on normal mucosa, and the data were compared. The samples were obtained from patients affected by histologically proven adenocarcinomas and synchronous adenomas of the bowel 48h after intravenous injection of HPD (3 mg/kg bodyweight), that is, the time interval usually required for photodynamic therapy. The intensity of fluorescence of the adenomas was a little lower than that observed from adenocarcinomas, but was higher than that from the surrounding mucosa. The fluorescence spectra from adenomas and from adenocarcinomas showed three main emission bands centred at about 630, 670 and 700 nm. The relative amplitudes of the band at 630 and 670 nm in benign and malignant colorectal tumours varied with the excitation wavelength, depending on the different physicochemical state of the accumulated drug. A further analysis, performed 72 h after administration, indicated the existence of an intratissue turnover of the porphyrins.     

In vivo nuclear imaging studies of uptake and retention of Tc-99m-labelled HpD in a murine tumour

The in vivo uptake of Tc-99m-labelled HpD in a murine tumour has been investigated using nuclear imaging techniques. Eighty-four per cent of the palpable tumours were visualized with good contrast resolution. The peak tumour-to-surrounding-normal-tissue ratio of 5:1 was at 4 h post-injection indicating the optimum time of imaging. The high level of HpD in the blood-pool component of the tumour could indicate that photodynamic therapy administered within 2 h after intravenous injection (early PDT) could lead to damage of tumour vasculature and tumour necrosis. The therapeutic response achieved by this early method needs to be investigated.     

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. Paper received 9 April 2001; accepted after revision 28 September 2001.     

光动力治疗人胆管癌细胞荷瘤裸鼠的实验研究

目的研究光动力疗法(photodynamic therapy,PDT)对人胆管癌荷瘤裸鼠的治疗效果,探讨其抗肿瘤性、安全性及腹腔注射和瘤内注射光敏剂两种不同给药途径疗效的差异。方法人胆管癌细胞QBC939接种于Balb/c裸小鼠皮下,建立荷瘤动物模型。以血卟啉衍生物(HpD)作光敏剂,采用腹腔内和瘤内注射2种不同给药方式,后以波长630 nm的激光照射肿瘤组织,观察PDT后肿瘤体积变化和病理改变。结果接受光动力治疗的两组肿瘤生长速度明显减慢,瘤内局部注射给药组疗效与腹腔给药组差异无统计学意义(P>0.05);组织学检查见肿瘤组织有广泛坏死,各组裸鼠心、肝、肺、肾组织切片未见病理性结构改变。结论HpD,PDT对人胆管癌荷瘤裸鼠的肿瘤组织有杀伤作用,使肿瘤生长减慢;HpD-PDT杀伤胆管癌移植瘤的深度可达0.8cm;在本实验光照条件下的PDT治疗是安全的。     

Comparative study of the phototoxicity of two chrolin type photosensitizers, ATX-S10(Na) and verteporfin, on vascular endothelial and retinal pigment epithelial cells

BACKGROUND AND OBJECTIVES: To compare the phototoxicity in photodynamic therapy (PDT) of ATX-S10(Na) and Verteporfin on human microvascular endothelial cells (HMVEC), vascular endothelial cells of monkey choroid and retina (CRVEC), and human retinal pigment epithelial cells (HRPE). STUDY DESIGN/MATERIALS AND METHODS: PDT was performed in two different ways. In short dye-exposure PDT, HMVEC and CRVEC were exposed to each photosensitizer for 5 minutes followed by laser irradiation of 670 nm wavelength for ATX-S10(Na) or 689 nm for Verteporfin without washing out the photosensitizer in the medium. In long dye-exposure PDT, the cells were exposed to photosensitizers for times ranging from 5 minutes to 2 hours, washed out the photosensitizers, followed by laser irradiation in a fresh medium. PDT was performed on HRPE with PDT doses that resulted in damaging 90% of the HMVEC (ED(90)). Phototoxicity was determined by MTS Assay 1 day after PDT. RESULTS: The degree of phototoxicity depended on the dye concentration, laser dose, and dye exposure time. In short dye-exposure PDT on HMVEC with a laser dose of 50 J/cm(2), the ED(90) was 6.3 microg/ml of ATX-S10(Na) and 0.04 microg/ml of Verteporfin, while in long dye-exposure PDT the ED(90) was 50.0 microg/ml of ATX-S10(Na) and 0.04 microg/ml of Verteporfin when the medium was supplemented with 5% fetal calf serum. The phototoxic rate on HMVEC was higher when the medium contained 5% as contrasted with 10% of serum. In short dye-exposure PDT, the ED(90) of CRVEC was 100 microg/ml of ATX-S10(Na) and an irradiance of 100 J/cm(2), and 0.08 microg/ml of Verteporfin and an irradiance of 100 J/cm(2) when the medium was supplemented with 10% serum. With some doses of short dye-exposure PDT, the ATX-S10(Na) achieved higher phototoxic rates on HMVEC and CRVEC than on the HRPE. However, long dye-exposure PDT with ATX-S10(Na) and short and long dye-exposure PDT with Vereteporfin failed to obtain higher phototoxic rates on HMVEC and CRVEC than on HRPE. CONCLUSIONS: Verteporfin had a higher phototoxicity than ATX-S10(Na) on HMVEC and CRVEC. The CRVEC resisted more than HMVEC following PDT with both photosensitizers. In short dye-exposure PDT, ATX-S10(Na) had a more selective phototoxicity on HMVEC and CRVEC than on HRPE.     

Reciprocity of exposure time and irradiance on energy density during photoradiation on wound healing in a murine pressure ulcer model

BACKGROUND: Energy density and exposure time reciprocity is assumed and routinely used in low-level light therapy (LLLT) regimens. This study examined dose reciprocity effects on wound healing. METHODS: Pressure ulcers were created on seven groups of C57/BL mice (n = 18). Photoradiation was administered (18 days; 5 J/cm(2)/day @ 670 nm) using a custom LED apparatus and treatment matrix varying both intensity and exposure. Control animals were treated similarly, without photoradiation. Ulcer staging was performed using a standardized scale. Changes in stage, wound area and wound closure rates were measured. Histology was performed. RESULTS: Photostimulatory effects at day 7 occurred with parameters of 125 seconds @ 40 mW x 1/day; 625 seconds @ 8 mWx1/day; 62.5 seconds @ 40 mWx2/day; and 312.5 seconds @ 8 mWx2/day; and at day 18 using 625 seconds @ 8 mW and 312.5 seconds @ 8 mWx2/day. Statistically significant increases in wound closure rates occurred using 625 seconds @ 8 mW; 62.5 seconds @ 40 mWx2/day; and 312.5 seconds @ 8 mWx2/day treatments. Mean ulcer grade scores were similar to controls. CONCLUSIONS: Varying irradiance and exposure time to achieve a specified energy density affects phototherapy outcomes in this model. Variation of exposure time and irradiance may account for conflicting results in the literature. Further studies of these effects are warranted.     

Effect of pulsed electromagnetic field therapy on prostate volume and vascularity in the treatment of benign prostatic hyperplasia: A pilot study in a canine model

BACKGROUND

Benign prostatic hyperplasia (BPH) is a result of urogenital aging. Recent studies suggest that an age‐related impairment of the blood supply to the lower urinary tract plays a role in the development of BPH and thus may be a contributing factor in the pathogenesis of BPH. The canine prostate is a model for understanding abnormal growth of the human prostate gland. We studied the efficacy of pulsed electromagnetic field therapy (PEMF) in dogs to modify prostate blood flow and evaluated its effect on BPH.

METHODS

PEMF (5 min, twice a day for 3 weeks) was performed on 20 dogs affected by BPH. Prostatic volume, Doppler assessment by ultrasonography, libido, semen quality, testosterone levels, and seminal plasma volume, composition and pH were evaluated before and after treatment.

RESULTS

The 3 weeks of PEMF produced a significant reduction in prostatic volume (average 57%) without any interference with semen quality, testosterone levels or libido. Doppler parameters showed a reduction of peripheral resistances and a progressive reduction throughout the trial of the systolic peak velocity, end‐diastolic velocity, mean velocity, mean, and peak gradient of the blood flow in the dorsal branch of the prostatic artery. The pulsatility index and the resistance index did not vary significantly over time.

CONCLUSIONS

The efficacy of PEMF on BPH in dogs, with no side effects, suggests the suitability of this treatment in humans and supports the hypothesis that impairment of blood supply to the lower urinary tract may be a causative factor in the development of BPH. Prostate 74:1132–1141, 2014. © 2014 The Authors. The Prostate published by Wiley Periodicals, Inc.