Cancer immunophotodetection and immunophototherapy

Some dyes can be used for cancer diagnosis and therapy. Following administr ation, the dye concentrate with some specificity in the tumor and can react to an irradiation with light. Some excited dyes can be fluorescent allowin g detection of very small tumors. Some other dye can be phototoxic and lead to the destruction of the tumor. These attractive techniques are however l imited because of the too low tumor specificity of the currently used dyes (hematoporphyrin and phthalocyanine). A new strategy has be developed in wh ich the fluorescent or phototoxic dye is coupled to an antibody directed ag ainst a tumor associated antigen. This approach allow the selection of the dye only for its optimal photochemical properties, the antibody being used as carrier to concentrate the dye in the tumor. Many experimental immunopho totherapy studies have been performed with different phototoxic dyes. Some results are encouraging but the involved mechanisms are complex and they li mit the current clinical applications of immunophototherapy. Concerning imm unophotodetection, two dyes have been coupled to anti-tumor antibodies: flu orescein and indocyanin. The antibody-dye conjugates have been evaluated in experimental studies and in pilot clinical trials. The most recent results concern the use of this technique in intraoperative situation and to visua lize neo-vascularization. Immunophotodetection gives a very precise image o f tumors. The detected tumor nodules are in the millimeter range. However, according to the limited light pathway in the tumor, this technique can be applied only to cutaneous areas, endoscopy accessible areas and intraoperat ive situations. Immunophotodetection is an attractive imaging technique usi ng antibodies.