Hyperthermic potentiation of photodynamic therapy employing Photofrin I and II: comparison of results using three animal tumor models

Enhancement of Photodynamic Cancer Therapy by Physical and Chemical Factors

The viable use of photodynamic therapy (PDT) in cancer therapy has never been fully realized because of its undesirable effects on healthy tissues. Herein we summarize some physicochemical factors that can make PDT a more viable and effective option to provide future oncological patients with better-quality treatment options. These physicochemical factors include light sources, photosensitizer (PS) carriers, microwaves, electric fields, magnetic fields, and ultrasound. This Review is meant to provide current information pertaining to PDT use, including a discussion of in vitro and in vivo studies. Emphasis is placed on the physicochemical factors and their potential benefits in overcoming the difficulty in transitioning PDT into the medical field. Many advanced techniques, such as employing X-rays as a light source, using nanoparticle-loaded stem cells and bacteriophage bio-nanowires as a photosensitizer carrier, as well as integration with immunotherapy, are among the future directions.

Porphyrin-based photosensitizers and the corresponding multifunctional nanoplatforms for cancer-imaging and phototherapy

This review article briefly describes: (a) the advantages in developing multifunctional nanoparticles for cancer-imaging and therapy, (b) the advantages and limitations of most of the porphyrin-based compounds in fluorescence imaging and photodynamic therapy (PDT), (c) problems associated with current Food and Drug Administration (FDA) approved photosensitizers, (d) challenges in developing in vivo target-specific PDT agents, (e) development of porphyrin-based nuclear-imaging agents (PET, SPECT) with an option of PDT, (f) the importance of light dosimetry in PDT, (g) the role of whole body or local hyperthermia in enhancing tumor-uptake, tumor-imaging and phototherapy and finally, (h) the advantages of photosensitizer-gold nanocages (Ps- Au NC) in photoacoustic and PDT.

Combined concurrent photodynamic and gold nanoshell loaded macrophage-mediated photothermal therapies: an in vitro study on squamous cell head and neck carcinoma

BACKGROUND AND OBJECTIVE

Treatment modalities, such as hyperthermia and photodynamic therapy (PDT) have been used in the treatment of a variety of head and neck squamous cell carcinoma (HNSCC), either alone or as an adjuvant therapy. Macrophages loaded with gold nanoshells, which convert near-infrared light to heat, can be used as transport vectors for photothermal hyperthermia of tumors. The purpose of this study was to investigate the effects of combined macrophage mediated photothermal therapy (PTT) and PDT on HNSCC cells.

STUDY DESIGN/MATERIALS AND METHODS

Gold nanoshell loaded rat macrophages either alone or combined with human FaDu squamous cells in hybrid monolayers were subjected to PTT, PDT, or a simultaneous combination of the two light treatments. Therapies were given concurrently employing two laser light sources of λ = 670 nm (PDT) and λ = 810 nm (PTT), respectively.

RESULTS

Significant uptake of gold nanospheres (AuNS) by rat alveolar macrophages was observed thus providing the rationale for their use as delivery vectors. Viability of the AuNS-loaded Ma was reduced to 35 and 12% of control values at an irradiance of 14 or 28 W/cm(2) administered over a 5 minute period respectively. No significant cytotoxicity was observed for empty Ma for similar PTT exposure. AlPcS2a mediated PDT at a fluence level of 0.25 J/cm(2) and PTT at 14 W/cm(2) irradiance had little effect on cell viability for the FaDu/Ma (ratio 2:1) hybrid monolayers. In contrast, combined treatment reduced the cell viability to less than 40% at these same laser power settings.

CONCLUSIONS

The results of this study provide proof of concept for the use of macrophages as a delivery vector of AuNS for photothermal enhancement of the effects of PDT on squamous cell carcinoma. A significant synergy was demonstrated with combined PDT and PTT compared to each modality applied separately.

Enhanced cytotoxic effects of 5-aminolevulinic acid-mediated photodynamic therapy by concurrent hyperthermia in glioma spheroids

During photodynamic therapy (PDT) both normal and pathological brain tissue, in close proximity to the light source, can experience significant temperature increases. The purpose of this study was to investigate the anti-tumor effects of concurrent 5-aminolevulinic acid (ALA)-mediated PDT and hyperthermia (HT) in human and rat glioma spheroids. Human or rat glioma spheroids were subjected to PDT, HT, or a combination of the two treatments. Therapies were given concurrently to simulate the conditions that will occur during patient PDT. Predictions of diffusion theory suggest that brain tissue immediately adjacent to a spherical light applicator may experience temperature increases approaching 8 degrees C for laser input powers of 2 W. In the in vitro model employed here, HT had no effect on spheroid survival at temperatures below 49 degrees C, while sub-threshold fluence PDT results in only modest decrease in survival. HT (40-46 degrees C) and PDT interact in a synergistic manner if the two treatments are given concurrently. The degree of synergism increases with increasing temperature and light fluence. Apoptosis is the primary mode of cell death following both low-fluence rate PDT and combined HT + PDT.

Photodynamic therapy and hyperthermia as an adjuvant modality in preventing tumor recurrence

BACKGROUND AND OBJECTIVE

The objective of this study was to determine the relative efficacy in preventing tumor recurrence by photodynamic therapy (PDT), and by ablative CO2 laser surgery followed by PDT, compared to ablative surgery alone (negative control) or ablative surgery followed by a course of hyperthermia (positive control).

STUDY DESIGN/MATERIALS AND METHODS

The cheek pouches of 36 hamsters were treated with 0.5% 9,10 dimethyl-1,2-benzanthracene in acetone three times a week. After 12 weeks all animals showed tumors of their cheek pouches and were divided into four groups. In groups number I, II, and III, all visible tumors were removed by aid of a CO2 laser. Animals of group I did not receive any further treatment. After tumor resection, the cheek pouches in group II were treated with hyperthermia by aid of a Nd:YAG laser and a temperature of 43 degrees C for 30 minutes. In group III after resection of the tumors, the cheek pouches were treated with PDT (75mW/cm2 175J/cm2--3mg/kg Photofrin i.p./24h). In group IV, the tumors were not excised, instead they were only treated with PDT (as above). All animals were observed for 50 days for any signs of tumor recurrence.

RESULTS

In group I (CO2) all tumors (100%) recurred within 50 days. In group II (CO2 + hyperthermia) 61%, in group III (CO2 + PDT) 27.7%, and in group IV (PDT) 50% of all tumors recurred. The first signs of recurrence could be seen in group I, followed by groups II and IV. Group III was the last one presenting tumor recurrence.

CONCLUSIONS

The combination of CO2 surgery and PDT produced significantly better results than CO2 surgery or PDT alone, and better than the combination of CO2 surgery and hyperthermia.

Effects of 780 nm diode laser irradiation on blood microcirculation: preliminary findings on time-dependent T1-weighted contrast-enhanced magnetic resonance imaging (MRI)

Laser therapy by low light doses shows promising results in the modulation of some cell functions. Various clinical studies indicate that laser therapy is a valuable method for pain treatment and the acceleration of wound healing. However, the mechanism behind it is still not completely understood. To explore the effect of a low-power diode laser (lambda = 780 nm) on normal skin tissue, time-dependent contrast enhancement has been determined by magnetic resonance imaging (MRI). In the examinations, six healthy volunteers (four male and two female) have been irradiated on their right planta pedis (sole of foot) with 5 J/cm2 at a fluence rate of 100 mW/cm2. T1-weighted magnetic resonance imaging is used to quantify the time-dependent local accumulation of Gadolinium-DPTA, its actual content in the local current blood volume as well as its distribution to the extracellular space. Images are obtained before and after the application of laser light. When laser light is applied the signal to noise ratio increases by more than 0.35 +/- 0.15 (range 0.23-0.63) after irradiation according to contrast-enhanced MRI. It can be observed that, after biomodulation with light of low energy and low power, wound healing improves and pain is reduced. This effect might be explained by an increased blood flow in this area. Therefore, the use of this kind of laser treatment might improve the outcome of other therapeutic modalities such as tumour ionizing radiation therapy and local chemotherapy.

Effects on the mitosis of normal and tumor cells induced by light treatment of different wavelengths

OBJECTIVE

Although the background of laser therapy by means of low level energy and power is still only partially understood, there are nevertheless promising reports from clinical studies concerning pain treatment, the acceleration of wound healing, and the modulation of cell functions. In order to contribute to the understanding of such a phototherapeutic procedure cell experiments were performed.

MATERIALS AND METHODS

The influence of light (lambda = 410, 488, 630, 635, 640, 805, and 1,064 nm and broad band white light) on the proliferation of cells was investigated on skeletal myotubes (C2), normal urothelial cells (HCV29), human squamous carcinoma cells of the gingival mucosa (ZMK1), urothelial carcinoma cells (J82), glioblastoma cells (U373MG), and mamma adenocarcinoma cells (MCF7) in a computer-controlled light treatment chamber. The cellular response was tested by way of the following methods: The rate of mitosis was determined by counting the single cells after Orcein-staining. The proliferation index measurements were based on the BrdU incorporation during the DNA synthesis. Statistics were performed using unpaired Student's t-test procedures, stating P < 0. 05 to be significant and P>0.05 not to be significant.

RESULTS

Twenty-four hours after light treatment, a significant increase in the mitotic rate of J82 and HCV29 cells was determined when illuminated with lambda = 410 nm, lambda = 635 nm and lambda = 805 nm, respectively. C2 cells showed an increase only after lambda = 635 nm illumination. In all three cell lines, a maximum mitotic rate was determined after an irradiation between 4 and 8 J/cm(2), while a reduced mitotic rate was measured at 20 J/cm(2). MCF7, U373MG, and ZMK1 cells showed a slight decrease in the mitotic rate with increasing irradiation independent of the wavelength used. When an irradiation of 20 J/cm(2) was applied, all cell lines showed a slight decrease compared to the controls independent to the wavelength used. White light as well as lambda = 1,064 nm does not affect the mitotic rate in this irradiation range. No significant differences in the effects could be determined when the irradiance changed between 10 and 150 mW/cm(2) at certain irradiation values. The BrdU test did not show any significant alterations with respect to possible light induced processes compared to the controls.

CONCLUSIONS

Dependent upon the irradiation parameter, light of a defined wavelength does affect the mitotic rate of both normal as well as tumor cells. It could be hypothesized that the action spectra of the cellular response indicate the participation of endogenous porphyrins and cytochromes as primary photoreceptors. Taking into account all light induced processes, the term biomodulation should preferably be used.

Biomodulative effects induced by 805 nm laser light irradiation of normal and tumor cells

The influence of light emitted from a diode laser centred at lambda = 805 nm was investigated on murine skeletal myotubes (C2), normal urothelial cells (HCV29), human squamous carcinoma cells of the gingival mucosa (ZMK) and urothelial carcinoma cells (J82) in a computer-controlled irradiation chamber. Cells were treated with varying fluences between 0 and 20 J cm-2. The response was tested by analysis of the mitotic index using single cell counting after Orcein staining and proliferation index based on BrdU incorporation during DNA synthesis. While the mitotic index of C2, HCV29 and J82 cells increased at a fluence of 4 J cm-2, irradiation with fluences of 20 J cm-2 resulted in a slight decrease. ZMK tumor cells showed a decrease of the mitotic index with both fluences. No significant differences could be determined when using irradiances between 10 mW cm-2 and 150 mW cm-2. The BrdU test after irradiation showed no significant effects compared to the controls in each cell line.

Photodynamic therapy in gynaecological neoplastic diseases

Since 1982, our department has used photodynamic therapy (PDT) in the treatment of loco-regional recurrences of gynaecological cancers. We have treated 26 patients in this time. In the majority of cases the site of vaginal recurrences was the vaginal vault. The light sources were an Argon-dye laser (Meditec) and, in some cases, a CO2 laser. The light dose ranged between 60 and 500 J cm-2. The photosensitizing drug used was Hematoporphyrin (HP) (Monico Farmaceutici) at the dose of 5 mg kg-1 body weight. Patients were evaluated 45 days after the treatment with a gynaecological examination and after 75-90 days with a vaginal smear. The results were divided into 2 groups: objective and symptomatic. The symptomatic response concerned only the patients treated with a palliative aim and, in this case, a complete response (CR) was a complete absence of symptoms at least for 60 days. In this group the complete response rate was 66%. In the curative group, the complete response was a cytological and/or histological absence of lesions. In this group we had 12 CR (70.58%). The survival rate was also evaluated. A significant review of the photodynamic therapy in gynaecological neoplasms has also been done.

Interstitial laser treatment of malignant tumours: initial experience

This is a prospective pilot investigation of interstitial laser treatment. Twelve patients were treated at 13 sites: seven patients had metastatic or primary liver cancer (with a total of 21 tumour nodules), two had pancreatic carcinoma and four patients had disease at other sites. Treatments were performed with an Nd-YAG laser, using a high power (6 or 10 W), short-time (5 min) technique or a feedback system for temperature regulation at low power (3 W) for 12-16 min. Treatment with high power invariably resulted in rapid carbonization of tissue, which may have contributed to the postoperative death in one patient. The local effect of treatment could be evaluated in 13 hepatic tumours (1.0-10 cm in diameter): 100% necrosis was seen in five and >50% necrosis in the remaining eight. Two tumours were eradicated, five became smaller, and six remained unchanged in size or showed continued growth. Treatment removed or alleviated symptoms in 7/8 symptomatic patients. The feedback system made it possible to avoid carbonization and allowed better control of the tissue temperature. The main problem with either method was to monitor tissue changes in real time, and ultrasonography was found to be of little help in this respect. It is concluded that interstitial laser treatment is a promising method for treatment of tumours. Further development should focus on real-time monitoring and increased volume effect without carbonization.

Temperature control and light penetration in a feedback interstitial laser thermotherapy system

The aim of this study was to describe the performance of a closed loop interstitial laser thermotherapy system in processed liver and to demonstrate its suitability for treating a vascularized tumour in vivo. The thermotherapy system consisted of an Nd: YAG laser and a temperature feedback circuit including an automatic thermometry system and thermistor probes. Experiments in processed liver were performed with a sapphire probe and temperature control at a distance of 10 mm. In most experiments at 1-2 W, and in half of the experiments at 3 W, there was no carbonization, a moderate change in the light penetration and excellent control of the temperature. In experiments with output powers of 4-5 W there was carbonization with rapid deterioration of light penetration and impaired control of the temperature. Carbonization affected the distribution of temperatures, which were lower below, and higher above, the laser tip in experiments with carbonization as compared to experiments without carbonization. Treatment of an adenocarcinoma implanted into rat liver was performed at 2 W with a bare fibre and without blood inflow occlusion. The feedback thermistor probe was placed 3 mm outside the margin of the tumour (largest diameter 9.5 +/- 0.3 mm (mean +/- SEM)). Temperature control and light penetration characteristics were similar to those found in vitro. No tumour could be demonstrated at sacrifice 6 days later. It is concluded that a closed loop feedback system can produce stable and reproducible local hyperthermia, that it performs better when carbonization is avoided and light penetration is preserved and that it has a great potential for interstitial thermotherapy of malignant tumours.

A mathematical model for predicting the temperature distribution in laser-induced hyperthermia. Experimental evaluation and applications

A time-dependent mathematical model for the heat transfer in laser-induced hyperthermia has been developed. The model calculates the temperature distribution in surface-irradiated tissues. Good agreement was found between the predictions of the model and in vitro experimental results obtained for bovine liver irradiated with an expanded beam from a Nd:YAG laser. Surface evaporation of water was included in the model and experimentally verified. The discrepancy between the measured and the calculated rise in temperature at three different depths on the axis of symmetry of the irradiating beam was found to be less than 5% after 15 min of irradiation. When irradiating in air and not accounting for the surface evaporation in the model, the accuracy of the model predictions was only 75-80%. The model was then used to investigate the influence of surface evaporation of water on the total temperature distribution theoretically in a clinically relevant case. From the numerical simulations, it was shown that, simply by providing a moistened liver surface, the maximum steady-state temperature could be forced into the tissue to a depth of 4 mm. It was also shown that, by employing the numerical model during the initial phase of hyperthermia treatment, overshooting of the temperature during the transient thermal build-up time could be prevented.

Gynecologic cancer recurrences and photodynamic therapy: our experience

The incidence of locoregional recurrences of gynecological tumors is still a major problem. Many authors suggest that it is the major cause of death in patients affected by cervical-endometrial cancers. The results achieved by retreating these patients with conventional therapies are still unsatisfactory. Since 1982, in our department, we have been using photodynamic therapy (PDT) for treatment of locoregional recurrences in gynecological cancers. We have treated 26 patients. In the majority of the cases, vaginal recurrences were on the vaginal vault. Out of 26 cancers, 17 were epidermoid cancers. Lasers used were the argon dye laser (Meditec) and, in some cases, the CO2 laser. Light dose ranged between 60 and 500 J/cm2. The photosensitizing drug used was hematoporphyrin (HP) (Monico Farmaceutici, Venezia, Italy) at a dose of 5 mg/kg body weight. Patients were evaluated 45 days after treatment with gynecological examination and again after 75-90 days with a vaginal smear. Results were divided into 2 groups: objective and symptomatic. The symptomatic response concerned only patients treated with a palliative aim and, in this case, a complete response (CR) was a complete absence of symptoms for at least 60 days. In this group the complete response rate was 66.6%. In the curative group, the complete response was a cytological and/or histological absence of lesion. In this group we had 12 CR (70.58%). The survival rate of patients treated only with PDT ranged between 3 and 92 months (mean 50.7 months). No major acute or side effects were recorded.

Interaction of photodynamically induced cell killing and dark cytotoxicity of rhodamine 123

Loss of clonogenicity of Chinese hamster ovary (CHO) cells, murine L929 fibroblasts and human bladder carcinoma T24 cells caused by photodynamic treatment (PDT) with hematoporphyrin derivative (HPD) is synergistically enhanced by subsequent incubation with rhodamine 123 in the dark. For CHO and L929 cells this synergistic interaction can be explained by an increased uptake of rhodamine 123 as the result of the photodynamic treatment. With aluminum phthalocyanine (AIPC) as photosensitizer only additive effects were observed in the three cell lines. Incubation in the dark with rhodamine 123, followed by a photodynamic treatment with HPD, resulted in an antagonistic interaction with regard to loss of colony formation. With AIPc the combination of treatments resulted in an additive effect with L929 and T24 cells, whereas with CHO cells a slight antagonistic interaction was observed. An antagonistic effect was also observed in model experiments, treating histidine photodynamically with HPD and measuring oxygen consumption. A possible explanation of these results could be an interaction or complex formation of rhodamine 123 with HPD resulting in a diminished singlet oxygen production. With AIPc this does not take place.

Adjuvant intraoperative photodynamic therapy diminishes the rate of local recurrence in a rat mammary tumour model

The use of photodynamic therapy (PDT) as an adjunct to curative tumour resection was investigated in a tumour recurrence model, using rat mammary adenocarcinoma BN472. Tumours were inoculated subcutaneously in 60 animals and resected after 21 days of growth. Immediately after removal, the operation site was exposed to 320-450 nm light of 0.1 W cm-2 and 60 J cm-2 after photosensitisation with either Photofrin (5 mg kg-1 i.v. 48 h before illumination) or 5-aminolaevulinic acid (ALA) (2 mg ml-1 in drinking water for 9 days). Porphyrin concentrations were measured in tissue samples. After 28 days, animals treated with adjunctive PDT had a significantly longer tumour-free interval than controls (P < 0.01); median 25 days (Photofrin), 18 days (ALA), 14 days (controls). Moreover, in the PDT groups significantly fewer rats had lymph node metastasis. A prophyrin concentration ratio between tumour and mammary tissue of 2:1 was found after Photofrin and 4:1 after ALA. The results indicate that adjuvant intraoperative PDT may be a safe and effective method of destroying residual tumour, thereby preventing locoregional tumour recurrence.

The effect of hypothermia and hyperthermia on photodynamic therapy of normal brain

The effect of whole body hyperthermia and hypothermia in conjunction with photodynamic therapy (PDT) was determined on normal rat brain. Hyperthermia animals (Group I, n = 18) were warmed until their core body temperature reached 40 degrees C, (brain temperature, 39.7 +/- 0.5 degree C) and maintained at 40 +/- 1 degree C for 30 minutes prior to and after PDT. Hypothermia (Group II, n = 31) animals were cooled to 30 +/- 1 degree C (brain temperature, 29.3 +/- 0.4 degree C) for 1 hour. PDT treatment was performed, and the body temperature of the animals was maintained at 30 degrees C for 2 hours post-PDT. A population of animals was subjected to PDT under normothermic (Group III, n = 16; body temperature, 37 +/- 1 degree C; brain temperature, 36.7 +/- 0.8 degree C) conditions and treated in a manner identical to that of hyperthermic animals. PDT was performed with 17 J/cm2, 35 J/cm2, or 70 J/cm2 (100 mW/cm2). Photofrin (Quadralogic Technologies Ltd., Vancouver, Canada) (12.5 mg/kg) was injected intraperitoneally 48 hours prior to laser treatment on all three groups. Wet-dry weight measurements were obtained on a separate set of all three groups of animals (n = 27). Cortical lesion depths were measured, and pathological evaluation was made at 24 hours post-PDT. No difference in the wet-dry weight measurements or histopathology was present between the three groups of animals. Lesion depths for Group I animals did not significantly differ from Group III animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Temperature rise in tumor tissue during high-dose-rate photoradiation

The bioheat transfer equation and optical diffusion theory are used to develop a mathematical model for describing the thermal field in a spherical tumor and its surrounding normal tissue resulting from photoradiation. Analytical solutions to the model equations are presented for determining both the steady-state and transient temperature profiles. The effect of the optical and thermal properties of the surrounding normal tissue on the thermal field generated within the tumor is explored.

Vascular function and tissue injury in murine skin following hyperthermia and photodynamic therapy, alone and in combination

The murine tail has been used as a model for injury to skin when hyperthermia (HT) and photodynamic therapy (PDT) using haematoporphyrin derivative, are used in combination. Skin injury by either agent alone was quantitated by the probability of tail necrosis as a function of dose of agent. 'Tolerance' doses of each modality were given and changes in skin vascular function were measured by the rate of clearance of 133Xenon. This was promptly inhibited but restored to normal by 7 days. The absolute numbers of hypodermal vessels of different sizes were measured in tail cross-sections and capillary numbers were found to be greatly reduced between 1 and 7 days, and restored to normal by 21-28 days. When a tolerance dose of PDT was followed at 1, 7, 21 and 28 days by test doses of HT, or vice versa, marked enhancements in probability of necrosis were observed when the interval was 1 or 7 days (Enhancement ratio (ER)PDT-HT = 1.5 and ERHT-PDT = 1.8). Prolonging the interval between modalities to 21-28 days spared the tissue (ERHT-PDT/21 DAYS = 1.1; ERPDT-HT/28 DAYS = 1.0). Close temporal apposition of PDT and HT, such as has been advocated to improve tumour control, may also increase injury to normal tissue through vascular effects common to both.

Interstitial photodynamic therapy in a rat liver metastasis model

Photodynamic therapy (PDT) of hepatic tumours has been restricted owing to the preferential retention of photosensitizers in liver tissue. We therefore investigated interstitial tumour illumination as a means of selective PDT. A piece of colon carcinoma CC531 was implanted in the liver of Wag/Rij rats. Photofrin was administered (5 mg kg-1 i.v.) 2 days before laser illumination. Tumours with a mean (+/- s.e.) diameter of 5.7 +/- 0.1 mm (n = 106, 20 days after implantation) were illuminated with 625 nm light, at 200 mW cm-1 from a 0.5 cm cylindrical diffuser and either 100, 200, 400, 800 or 1600 J cm-1. Control groups received either laser illumination only, Photofrin only or diffuser insertion only. Short-term effects were studied on the second day after illumination by light microscopy and computer-assisted integration of the circumference of damaged areas. Long-term effects were studied on day 36. To determine the biochemistry of liver damage and function, serum ASAT and ALAT levels were measured on day 1 and 2, and antipyrine clearance on day 1. Tumour and surrounding liver necrosis increased with light dose delivered (P < 0.001). Best long-term results were obtained at 800 J cm-1 with complete tumour remission in 4 out of 6 animals. No deterioration in liver function was found. The results of this study show the ability of interstitial PDT to cause major destruction of tumour tissue in the liver combined with minimal liver damage.

Microprocessor-controlled Nd:YAG laser for hyperthermia induction in the RIF-1 tumor

Near-infrared radiation from a Nd:YAG laser at 1,064 nm was used interstitially or superficially to induce hyperthermia in RIF-1 tumors in C3H male mice. A single 600-microns quartz fiber with a 0.5-cm cylindrical diffusor or a weakly diverging microlens at its distal end was used to deliver laser energy to tumors in the hind leg (mean volume = 100 mm3). Two thermocouples were inserted into each tumor. One thermocouple controlled a microprocessor-driven hyperthermia program (maximum output of 3.5 Watts) to maintain the desired temperature. Tumors were exposed to various temperature-time combinations (42-45 degrees C/30 min). Our initial results indicated that excellent temperature control to within 0.2 degrees C of the desired temperature at the feedback thermocouple was achievable during both superficial and interstitial heat treatments. Temperatures at the second thermocouple, however, were found to be lower by as much as 2.3 degrees C (using the cylindrical diffusor) or higher by up to 4.6 degrees C (using the microlens) when compared to the feedback thermocouple temperature. Several correlations were seen between total dose, tumor growth delay, percent skin necrosis, and temperature at the second thermocouple after several superficial and interstitial treatments. Statistically significant improvements in tumor growth delay (at 42 and 45 degrees C) and increased percent skin necrosis at all temperatures were observed after superficial versus interstitial treatment.

In vivo 31P NMR study of combined hyperthermia and photodynamic therapies of mammary carcinoma in the mouse

Although the sequence and time interval effects of combined photodynamic therapy (PDT) and hyperthermia tumor treatments have been studied using survival curves, tumor regrowth, and cloning assays, the metabolic response to combined treatment measured by nuclear magnetic resonance (NMR) spectroscopy has not yet been clarified. In this study, mammary carcinoma in the flank of C3H mice was subjected to PDT (12.5 mg/kg Photofrin II, 632 +/- 1 nm at 200 J/cm2) and water bath hyperthermia (43.5 degrees C, 30 min) with no delay or 4 h delay between treatments. In vivo 31P-NMR spectroscopy was employed to measure energy metabolism and pH of the tumors before and serially after treatment for up to 1 week. The data revealed significant differences in the time course of high energy phosphate levels between treatment combinations, which may reflect the biological effectiveness of the combined treatments. Our observations indicate that 31P-NMR spectroscopy can be used to evaluate the metabolic response of tumors to treatment with combined PDT and hyperthermia.

Hyperthermia potentiates the effects of aluminum phthalocyanine tetrasulfonate-mediated photodynamic toxicity in human malignant and normal cell lines

The purpose of this study was to examine the effects of photodynamic therapy utilizing aluminum phthalocyanine tetrasulfonate in vitro on several human malignant and normal cell types, with or without hyperthermia. Cells examined included normal skin fibroblasts, HT-1080 fibrosarcoma cells, SCC-25 (squamous cell carcinoma) and malignant melanoma cells. An argon-pumped continuous wave tunable dye laser at 675 nm was used as the light source, hyperthermia groups were heated to 42.5 degrees C, and radioisotope incorporation was used to measure DNA and protein synthesis as toxicity assays. Results showed an energy-dose, and A1PcS-concentration dependent toxicity in all cell lines examined, with moderate selectivity toward malignant cells. Hyperthermia alone was slightly toxic in melanomas and HT-1080 cell lines but had no effect in normal fibroblasts or SCC-25 cells. Hyperthermia synergistically potentiated the effects of PDT in all cell lines, and the combined modality was significantly more toxic in all malignant cell lines compared with normal cells. Thus, addition of hyperthermia to PDT protocols may enhance the efficacy of this treatment modality in vitro.

Nd:YAG laser hyperthermia treatment of rat mammary adenocarcinoma in conjunction with surface cooling

Electromagnetic radiation ranging from radiofrequency to microwave has classically been used to induce hyperthermia for treatment of cancer. This paper presents a new technique using near infrared radiation from an Nd:YAG laser in conjunction with surface cooling to induce hyperthermia in a rat tumor model. A CW Nd:YAG laser hyperthermia system was used to induce hyperthermic temperatures in chemically (DMBA) induced rat mammary adenocarcinomas. The laser was interfaced to a computer and a thermometry unit that provided feedback to control the tumor temperature between 43.2-43.5 degrees C. A thermocouple was placed at the base of the tumor and its temperature was used to control laser exposure. All tumors were 10 to 20 mm in diameter. Surface cooling methods investigated included forced air flow from a fan, forced oxygen flow plus an IV drip, and forced moist oxygen flow from a nebulizer. Twelve rat mammary adenocarcinomas have been treated with Nd:YAG laser hyperthermia. In 4 treatments, no surface cooling was employed. In one treatment the surface was cooled using oxygen flow plus IV drip. In 7 treatments the skin was cooled using the nebulizer technique. The nebulization provided the most effective and reproducible surface cooling. Nd:YAG laser hyperthermia delivered in conjunction with nebulizer surface cooling produced efficient heating of rat mammary adenocarcinomas. A mean temperature of 42.1 degrees C was obtained at the base of the tumors while the mean surface temperature was 37.0 degrees C.

Response of human endometrium and ovarian carcinoma cell-lines to photodynamic therapy

The response of the human gynecological carcinoma cell-lines HEC-1-A (endometrial carcinoma) and OvCar-3 (ovarian carcinoma) to photodynamic therapy in vitro was examined. The porphyrin compound Photosan III (Ph III) was used for photosensitization of the cells after incubation times of 24 h (HEC-1-A) and 48 h (HEC-1-A and OvCar-3). The Ph III doses varied from 0-10 micrograms/ml medium. Irradiation was performed with laser light at 630 nm. Irradiation doses up to 20 J/cm2 were applied at an irradiance of 40-100 mW/cm2. Cell vitality of the untreated control groups and of the therapy group was determined 48 h after irradiation, using the trypan blue exclusion test. The experimental results show that treatment of OvCar-3 cells with 10 J/cm2 resulted in a decrease in vitality dependent on photosensitizer dose (0-5 micrograms/ml, 48 h incubation time) but independent of the irradiance (40-100 mW/cm2). Complete cell death was observed after application of irradiation doses in the range of 5-20 J/cm2 combined with drug concentrations of 10-2.5 micrograms/ml, at a fixed incubation time of 48 h. HEC-1-A cells did not survive photodynamic therapy with 10 J/cm2 after incubation with 5 micrograms/ml for 48 h. After a shorter incubation time of 24 h, 10 micrograms/ml Ph III was necessary for the same effect. There was a maximum decrease in cell vitality when measured 48 h after irradiation. This was not improved at 72 h.

Laser-induced photodynamic therapy with aluminum phthalocyanine tetrasulfonate as the photosensitizer: differential phototoxicity in normal and malignant human cells in vitro

Photodynamic therapy (PDT) involves the use of laser or noncoherent light energy with photosensitizing dyes to induce a cytotoxic reaction in the target cells, resulting in cell injury and/or death. In this study, we have examined laser-induced phototoxicity in normal human skin fibroblasts and HT-1080 fibrosarcoma cells incubated with aluminum phthalocyanine tetrasulfonate (AlPcS) in vitro. The culture, laser, and photosensitizer parameters were varied in attempts to establish the conditions for differential cytotoxicity between normal and malignant human fibroblasts. Biochemical assays, as a measure of cytotoxicity, included [3H]thymidine incorporation (an index of DNA replication), [35S]methionine incorporation (a measure of protein synthetic activity), and the MTT assay (an indirect index of mitochondrial activity). In the absence of laser irradiation, AlPcS was non-toxic to both cell lines in concentrations up to 25 micrograms/ml. Laser light alone at 675 nm (the absorption maximum of AlPcS) had no effect on the cells at energy densities up to 16 J/cm2. In the presence of 3 or 10 micrograms/ml of AlPcS, both cell lines demonstrated marked energy-dependent toxicity. If an 8-h or a 24-h "efflux" period in AlPcS-free medium was allowed to take place prior to laser irradiation, normal fibroblasts were much less sensitive to PDT, whereas fibrosarcoma cells still exhibited a marked degree of toxicity. The results indicate that, under appropriate treatment conditions, AlPcS is capable of preferentially sensitizing a malignant mesenchymal cell line, while sparing its non-malignant normal cell counterpart.

Increased efficacy of photodynamic therapy of R3230AC mammary adenocarcinoma by intratumoral injection of Photofrin II

Photodynamic therapy consists of the systemic administration of a derivative of haematoporphyrin (Photofrin II) followed 24-72 h later by exposure of malignant lesions to photoradiation. We investigated the efficacy of this treatment after direct intratumoral injection of Photofrin II. This direct treatment regimen resulted in higher rates of inhibition of mitochondrial cytochrome c oxidase (5.13% J-1 cm-2 x 10(-1) and succinate dehydrogenase (3.14% J-1 cm-2 x 10(-1] in vitro at 2 h after intratumoral injection compared to rates of inhibition obtained after intraperitoneal drug administration: 0.51 and 0.42% J-1 cm-2 x 10(-1), respectively. A significant delay in tumour growth in vivo was observed in animals that received intratumoral injections 2 h before photoradiation compared to animals injected intraperitoneally at either 2 or 24 h before photoradiation. The treatment protocols were compared with control groups, consisting of Photofrin II administration intratumorally or intraperitoneally without photoradiation, or photoradiation in the absence of Photofrin II. These data indicate that the intratumoral injection regimen with Photofrin II enhanced the efficacy of photodynamic therapy. The greater delay in tumour growth observed after intratumoral administration of Photofrin II suggests a mechanism favouring direct cell damage.

Nd:YAG laser-induced interstitial hyperthermia using a long frosted contact probe

The heating potential of a closed loop interstitial hyperthermia system employing 1,064 nm laser light in conjunction with a long frosted contact probe was investigated in hind limb muscle of anesthetized dogs. The laser system was an Nd:YAG surgical laser modified with a single channel thermometry unit, a computer, a printer, and a computer-controlled laser exposure shutter. The long frosted laser probe was implanted into the muscle, and 3.12-5.00 Watts of laser power was delivered interstitially. Temperature distribution was measured in three dimensions around the frosted probe. The temperature distributions generated by this technique were satisfactory for producing desired hyperthermia temperatures in an approximately 3.5 cm3 cylindrical tissue volume. A multiple laser delivery system is needed to induce interstitial hyperthermia in large tumors. A significant potential for the long frosted contact probe may be its use in combining interstitial hyperthermia and interstitial photodynamic therapy. Using this technique, both modalities may be delivered while employing the same treatment setup.

Intraoperative phototherapy (PDT) and surgical resection in a mouse neuroblastoma model

This study evaluates the effect of intraoperative photodynamic therapy (PDT) using the multiline argon laser (488-514 nm) or the argon-dye laser (630 nm) combined with surgical resection compared with surgical resection alone in reducing the incidence of C1300 neuroblastoma recurrence in mice. In the control groups, surgical resection alone resulted in 86% +/- 12% tumor recurrence. Surgical resection and intraoperative lasing without photosensitizer resulted in 75% +/- 27% tumor recurrence with the argon-dye laser and 55% +/- 18% recurrence with the multiline argon laser. In the treatment groups, surgical resection and intraoperative PDT at 630 nm resulted in 56% +/- 19% tumor recurrence whereas surgical resection and intraoperative PDT at 488-514 nm resulted in 21% +/- 7% tumor recurrence. The cause for the decrease in local recurrence in the control group using the multiline argon laser is unknown, but could it be due in part to hyperthermic effects. Intraoperative PDT was an effective adjunct to surgical resection in preventing local recurrence in this tumor model.

Nd:YAG laser-induced hyperthermia in a mouse tumor model

Hyperthermic tumor response induced by 1,064-nm radiation from an Nd:YAG laser was investigated in DBA/2J female mice bearing the SMT-F mammary carcinoma. The measured temperature-depth profiles indicate that hyperthermic temperatures can be achieved in tumors ranging from 3 to 8 mm thick at power inputs on the order of 1 W. For small tumors, a 5-week complete response rate exceeding 50% required 45 minutes at 45.0 degrees C. Control of large tumors (6-8 mm thick) was not achieved. The observed tumor response rates are consistent with semiempirical time-temperature relations based on other heating modalities.