PHOTODYNAMIC THERAPY AS A TOOL FOR SUPPRESSING THE HEMATOGENOUS DISSEMINATION OF TUMOR-CELLS

The chance of most cancer patients surviving their disease is to a hig h degree dependent on the status of the metastatic processes. One gene ral route of cancer-cell dissemination is passive transport in the blo od stream, i.e., haematogenous dissemination. In this study we try to find an answer to the following question: is it possible to use photod ynamic therapy for suppressing the haematogenous dissemination of canc er cells? In first in vitro experiments we incubated CX1 cells (colon carcinoma cells) with two photosensitizers, Photofrin II and meso-tetr a(hydroxyphenyl) chlorin (mTHPC). We added the cells to fresh whole bl ood and irradiated the blood with suitable laser light in a flow-throu gh irradiation system. The tumour-cell survival fraction (SF) was dete rmined with plating efficiency. Using Photofrin II we observed a minim al tumour-cell survival in blood of SF = 3.5% and using mTHPC we measu red SF = 0.02%. These results encourage further investigations concern ing the use of photodynamic therapy for suppressing haematogenous diss emination. (C) 1998 Elsevier Science S.A. All rights reserved.