Genady Kostenich

Temperature monitoring during photodynamic therapy of skin tumors with topical 5-aminolevulinic acid application

Temperature monitoring during photodynamic therapy (PDT) with topical 5-aminolevulinic acid (ALA) cream application was performed on 22 patients with solar keratoses (SK) and basal cell carcinoma (BCC). The lesions were located on the forehead, nose, ear and cheek. Temperature measurements during photoirradiation, with a power density of 100 mW/cm2 from an incoherent light source (light delivery system for PDT), were carried out by noncontact (infrared thermal imaging radiometer) and contact (thermocouple) methods. Thermal imaging analysis revealed nonuniform temperature distribution in the irradiated areas. The temperature gradually increased from the peripheral to the central zone of the area. The results showed that photoirradiation induced heating of the skin tumors to 39.5-42.5 degrees C during the PDT procedure. The temperature of normal skin areas disposed symmetrically to the lesions on the contralateral side at the same conditions of irradiation (without prior ALA application) was about 42-43.5 degrees C. The surface temperature differences (delta T) between the normal and tumor tissues after 10 min of irradiation were 3.3 +/- 0.5 degrees C in the forehead areas, 2.5 +/- 0.4 degrees C in the nose areas and 0.8 +/- 0.3 degrees C in the ear areas.

The kinetics of protoporphyrin fluorescence during ALA-PDT in human malignant skin tumors

Fluorescence monitoring during photodynamic therapy (PDT) with the use of topical 5-aminolevulinic acid (ALA) was carried out in patients bearing superficial and nodular basal cell carcinomas (BCC), squamous cell carcinomas (SCC) and Kaposis sarcomas. A new diagnostic-therapeutic system based on an incoherent CW light source was used for fluorescence spectral measurements and imaging. The results showed that photoirradiation reduced ALA-induced protoporphyrin IX (PP) fluorescence in all tumors. The rate of PP photobleaching in superficial BCC and SCC tumors was significantly higher than in large nodular BCC tumors. The results showed that the differences in kinetics of fluorescence reduction could be attributed to the tumor thickness. One hour after photoirradiation with a light dose of 170 J/cm2 a phenomenon of re-appearance and recovery of PP fluorescence was observed in the large deeply penetrating BCC tumors and Kaposis sarcoma lesions. In such cases an additional light treatment was performed. The results of the study demonstrated that fluorescence monitoring is very appropriate for the definition of an optimal ALA-PDT clinical protocol.

In vivo photodynamic therapy with the new near-IR absorbing water soluble photosensitizer lutetium texaphyrin and a high intensity pulsed light delivery system

An in vivo fluorescence monitoring and photodynamic therapy (PDT) study was performed using the new photosensitizer lutetium texaphyrin (Lu-Tex). This photosensitizer is water soluble and has the additional advantage of strong absorption near 730 nm. C26 colon carcinoma was transplanted in the foot of BALB/c mice. In vivo fluorescence spectroscopy was applied to study Lu-Tex tissue distribution kinetics. For this purpose, fluorescence intensity both in the foot with the tumor and in the normal foot was measured in vivo by the laser-induced fluorescence (LIF) system. For PDT, both feet of the mice were irradiated simultaneously with the use of a new high intensity pulsed light delivery system, the Photodyne. The results of the LIF measurements showed that the maximal fluorescence intensity ratio between the normal and tumor bearing foot (FIR) was observed 24-48 h after the agent injection. Photoirradiation with doses from 90 to 240 J cm-2 (0.6 J cm-2 per 2 ms pulse, 1 Hz) 24 h after injection of Lu-Tex at a dose of 10 mg kg-1 caused significant tumor necrosis and delay in the tumor growth rate. The antitumor effect was enhanced with increasing light doses. Normal tissue response to PDT with Lu-Tex was determined as the damage index of the normal foot, which was irradiated simultaneously with the tumor bearing foot. The normal tissue response after PDT with Lu-Tex was compared with 5-aminolevulinic acid (ALA) induced protoporphyrin IX (PP), chlorin e6 (Chl) and Photofrin (PII) at the same values of antitumor effect. The results showed that at 50, 80 and 100% inhibition of tumor growth the orders of the values of normal foot damage indexes were as follows: ALA > Lu-Tex > or = PII > Chl, PII > ALA > Lu-Tex > Chl and PII > Lu-Tex > ALA > Chl respectively.

Photosensitization by the near-IR-absorbing photosensitizer lutetium texaphyrin: spectroscopic, in vitro and in vivo studies

The spectroscopic and biological properties of the new photosensitizer lutetium texaphyrin (Lu-Tex) were assessed in vitro and in vivo on a C26 colon carcinoma model, in comparison with hematoporphyrin (Hp), photofrin II (PII) and chlorin e6 (Chl). Strong binding of Lu-Tex to lipid bilayer membranes was observed. The results of confocal fluorescence microscopy on C26 cells showed that Lu-Tex was localized in small vesicles in the cytoplasm, possibly in the lysosomes, while Chl and Hp were distributed in larger cytoplasmic vesicles attributed to mitochondria. Scanning electron microscopy and X-ray microanalysis revealed that photodynamic therapy with Lu-Tex induced only slight damage to the cell membrane, leading to a delayed cell response. Chl and Hp caused significant structural damage to the outer cell membrane, resulting in ionic imbalance and fast cell death. The in vitro quantitative assessment of the relative efficiency per absorbed photon of the sensitizers revealed that Lu-Tex was less effective than Chl and Hp. However, the results of our in vivo study showed that at the same light and drug doses the anti-tumor efficiency of the agents was in the following order: Lu-Tex > Chl > PII. The strong in vivo anti-tumor effect of Lu-Tex can be explained by its higher integrated absorption in the long-wavelength range.

Photothermic treatment of pigmented B16 melanoma using a broadband pulsed light delivery system.

Pulsed photothermic treatment (PTT) of pigmented B16 mice melanoma tumors was carried out using a Photodyne incoherent light delivery system. Tumor heating with average temperature of 41-44 degrees C was observed during broadband photoirradiation (600-800 nm) at light doses of 60-120 J/cm(2) delivered using 0.6 J/cm(2) pulses (2 ms) at 1 Hz repetition rate. Electron microscopy of tumor samples revealed pronounced structural changes in microvasculature and melanosomes. Pulsed PTT caused damage to endothelial cells and vascular walls, swelling of mitochondria and melanosomal disruption without nuclear alteration. Significant tumor response with necrosis formation followed by tumor regression was observed by a tumor growth study after PTT at 120 J/cm(2).

Photodynamic Therapy: Basic Principles and Applications to Skin Cancer

autofluorescence Fluorescence arising from molecules occurring naturally in normal or diseased tissue. fluorescence Reemission of light by a molecule upon absorption of a light photon, with the wavelength of the emitted light being greater than that of the absorbed light. light-emitting diode A type of nonlaser light source in the form of small emitting elements, which may be arranged as a one or two-dimensional array for PDT treatments. Nd:YAG laser A type of laser emitting near-infrared light used to cut or ablate tissue by conversion of the light into heat upon absorption by the tissue. optical fiber A means of efficiently transmitting light energy over a distance, used in PDT to deliver light from a laser to the tissue. photodynamic The biological effect of light activation of a photosensitizer, usually in the presence of oxygen. photodynamic therapy (PDT) A treatment modality exploiting the use of light-activated drugs (photosensitizers). photosensitizer A molecule (drug) that can absorb light and be transformed to a biologically active excited state. singlet oxygen (O2) An excited state of oxygen generated by energy transfer from an excited photosensitizer molecule.