Photodynamic therapy as a tool for suppressing the haematogenous dissemination of tumour cells

The chance of most cancer patients surviving their disease is to a high degree dependent on the status of the metastatic processes. One general route of cancer-cell dissemination is passive transport in the blood stream, i.e., haematogenous dissemination. In this study we try to find an answer to the following question: is it possible to use photodynamic therapy for suppressing the haematogenous dissemination of cancer cells? In first in vitro experiments we incubated CX1 cells (colon carcinoma cells) with two photosensitizers, Photofrin II and mesotetra(hydroxyphenyl)chlorin (mTHPC). We added the cells to fresh whole blood and irradiated the blood with suitable laser light in a flow-through irradiation system. The tumour-cell survival fraction (SF) was determined with plating efficiency. Using Photofrin II we observed a minimal tumour-cell survival in blood of SF = 3.5% and using mTHPC we measured SF = 0.02%. These results encourage further investigations concerning the use of photodynamic therapy for suppressing haematogenous dissemination.