Outpatient Cancer Treatment by means of Photodynamic Therapy with Chlorin Derivatives
Photodynamic therapy (PDT) is founded upon the local activation of a photosensitizer accumulated in a tumor by means of light. In the presence of tissue oxygen, this activation causes a photochemical reaction that destroys tumor cells.
PDT advantages comparing to traditional techniques used for cancer therapy: high effectiveness and selectivity of the damage; a wide list of the indications (various localizations, radical and palliative courses, preoperative PDT, combined treatment); a limited number of contraindications; relative safety (no risk of surgical intervention, no heavy and systemic complications); easy to perform; a single procedure and multiple sessions are possible (if necessary); combination of diagnostic and curative aspects; well-tolerated by patients; photodynamic therapy may be performed at the outpatient unit; economic effectiveness. Nowadays the most widespread photosensitizers are hematoporphyrin derivatives (Photofrin, Photosun, Photohem). Photosensitizers of the first generation, however, have got a number of disadvantages: a low penetration of exciting light, which narrows the sphere of PDT usage; a long-lasting skin toxicity; low energy of light absorption.
For the last ten years there has been an intensive development of photosensitizers of the second generation with a short-time term of elimination and a bigger wavelength of exciting light, which provides more deep penetration into biological structures, as well as corresponds to other main requirements to photosensitizers. Such photosensitizers are Russian-made chlorin e6 derivatives Radachlorin and Photoditazine, as well as Belorussian compound Photolon, which have got corresponding permissions for clinical usage. Photodynamic therapy yields almost 100 % therapeutic efficiency. Photodynamic therapy of skin cancer normally requires a single session under outpatient conditions, whereas a routine X-ray therapy lasts for 2 to 3 weeks. In this sense, photodynamic therapy provides a much better economic efficiency with good healthy and cosmetic results. Photodynamic therapy has a similar effect in the case of other superficial malignant tumors. For example, it goes for breast cancer, uterus cancer, tongue cancer, melanoma, and other tumors.
We have got a big experience in using photosensitizers of the second generation from the group of chlorin e6 derivatives for the performance of PDT in order to treat skin cancer under outpatient conditions. Results of PDT treatment were assessed according to the following parameters: complete resorption was stated when there was no visual and palpated lesion confirmed by negative results of the hystological or cytological examination; partial resorption was stated when reduction of maximal size of the malignant node was by 50 %, as well as when there was visual absence of the tumor but malignant cells were revealed by morphological investigations (in such a way some recurrences after PDT were found); tumor reduction by less than half size was considered as no response.
The therapeutic effect was achieved in all patients who had been treated. The results of photodynamic therapy with chlorin e6 derivatives are estimated as good and excellent due to the preservation of the collagenous structure of tissues and the healing of a tissue defect after resorption of a tumor by type of reparation, but not scarring.
Photosensitizers of the chlorin e6 group have a high photodynamic activity and therapeutic effectiveness. They are rapidly eliminated from the organism and due to this do not cause long-lasting photosensitization. It completely solves the problem of long-lasting skin phototoxicity which is the basic drawback of the first generation photosensitizers which are clinically used. Due to rapid accumulation in a tumor and due to high contrast gradient the photosensitizers of chlorin e6 raw allow to reduce a curative session from some days up to some hours.
Photodynamic therapy with application of chlorin e6 derivatives under outpatient conditions is a comfortable and effective method of cancer treatment that provides good functional and cosmetic results.