Experimental photodynamic therapy in the treatment of lung tumor.

Abstract

e20515 Background: Study of the effect of photodynamic therapy (PDT) with Photoditazine using a high-energy laser at various periods after tumor transplantation on the dynamics of growth of experimental Lewis lung carcinoma in mice. Methods: The study included 176 male C57Bl6 mice weighing 18-20 g with Lewis lung carcinoma (LLC) transplanted subcutaneously. The animals received experimental PDT sequential overlapping of fields of influence (662 nm, 3 W, Photoditazine 25 mg/kg, 300 J/cm2). Animals received PDT on day 11 after the transplantation (experimental series I) and on day 21 (experimental series II). Experimental groups were divided in dependence on the exposure area (to the primary tumor -1gr, thorax (area of metastases)-2 gr and to both zones-3 gr). Animals with tumors without PDT were used as controls. Results: PDT with Photoditazine using the 3W laser stimulated the growth of primary tumor node. The degree of stimulation depended on the time of PDT. Increase in tumor sizes differed already on day 7 after PDT at various periods of the LCC growth. During PDT on the 11th day from the moment of tumor inoculation, the percentage of growth on the 7th day after the end of treatment was 60.7; 69.6 and 86.7% in groups 1, 2 and 3, respectively. In the groups of animals that underwent PDT on the 21st day of the growth of the grafted tumor on the 7th day after the end of treatment, the percentage of tumor growth was 20; 35.6 and 24.4% in groups 1, 2 and 3, respectively. Increase in the median survival was registered in experimental animals with PDT on 22.6% compared to control. A smaller increase in tumor volume was observed in animals receiving PDT to the primary tumor, and the group receiving therapy to both areas was in between. Conclusions: The study was shown that with an earlier initiation of PDT, a greater stimulation of tumor growth was revealed than with therapy at a later date. The revealed characteristics of the development of experimental LLC at PDT exposure allows further selection of parameters for photodynamic therapy regimens.