9. Experience of Using Photodynamic Therapy for Skin Cancer with

Chlorin e6 Photosensitizers under Outpatient Conditions

A.A.Radaev, E.Ph.Stranadko

Nowadays the most widespread photosensitizers are hematoporphyrin derivatives (Photofrin, Photohem). Photosensitizers of the first generation, however, have got a number of disadvantages: a low penetration of exciting light, which narrows the sphere of their 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 a deep penetration into biological tissues. 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 (PDT) for skin cancer normally requires a single session under outpatient conditions, whereas a routine close-focus X-ray therapy lasts for 2 to 3 weeks. In this sense, PDT provides a much better economic efficiency with good healthy and cosmetic results.

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.

The drug doses for Radachlorin and Photoditazine were 0.6 to 0.8 mg/kg, the drug-light interval (DLI) was from 1 up to 3 hours, the light dose was 100 to 250 J/cm2.

The drug dose for Photolon was 1.2 to 1.5 mg/kg, the DLI was 3 hours, and the light dose was 150 to 300 J/cm2.

Results of the PDT treatment were assessed according to the following parameters:

1. COMPLETE RESORPTION (CR) was stated when there was no visual and palpated lesion confirmed by negative results of the hystological or cytological examination.
2. PARTIAL RESORPTION (PR) was stated when reduction of maximal size of the malignant node was by 50 %, as well as when there was visual absence of a tumor, but malignant cells were revealed by morphological investigations (in such a way some recurrences after PDT were found).
3. Tumor reduction by less than half size or tumor status without changes was considered as NO RESPONSE (NR).

The therapeutic effect was achieved in all patients who had been treated (see the Table).

Table. Efficacy of PDT for skin cancer with chlorin e6 photosensitizers under outpatient conditions

CR – complete resorption; PR – partial resorption

The results of PDT with the chlorin e6 photosensitizers are estimated as good and perfect, 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.

Conclusion

Photosensitizers of the chlorin e6 group have 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 applied in the clinic. Due to rapid accumulation in the tumor and due to high “tumor/normal tissue” ratio the photosensitizers of the chlorin e6 raw allow to reduce the curative session from some days up to some hours.

PDT for skin cancer with chlorin e6 photosensitizers under outpatient conditions is a comfortable and effective method of the treatment that provides good functional and cosmetic results.