Background: Photodynamic therapy (PDT) is a well-known method of cancer treatment, during which some biologically active proteins are induced, while others are reduced in amount. In the present
study we checked whether PDT influences the concentration of Vascular-Endothelial Growth Factor (VEGF) in vivo. Most previous studies on VEGF have been done in vitro. In this paper we explored the hypothesis that VEGF levels correlate positively with tumor
growth and negatively with the time of survival of PDT-treated animals.
Material/Methods: We implanted a malignant tumour, BFS1 fibrosarcoma, into BALB/c mice and then treated them using a new photosensitizer, hydroxygallium (III) phthalocyanine tetrasulfonic acid
tetrasodium salt, BON-6. The administration of this compound was followed by light irradiation using a halogen lamp at 680 nm. VEGF concentrations were measured in sera from the mice and compared to the time of tumor growth.
Results: BON-6 was found to be effective in PDT. This feature was accompanied by low levels of VEGF after BON-6+PDT, and also prolongation of the time of survival of treated animals. The mice
which received BON-6+PDT survived 83.8 days (SD 10.23). The mean survival time in control groups did not exceed 35 days. Additionally, measurement of tumor size showed total regression in single cases after BON-6+PDT.
Conclusion: PDT, by decreasing VEGF serum levels, may influence the capability of tumor tissue to form new vessels.

Keywords: Fibrosarcoma - blood, Neovascularization, Pathologic - drug therapy