Experimental Study Of Photodynamic Therapy For The Treatment Of Transplanted Mice Forestomach Carcinomas

Photodynamic therapy (PDT) is a relatively new modality for the treatment of various types of malignant tumors in human. The procedure consists of systemically administering a light-sensitive drug, which either localizes in or is retained selectively by malignant tissue. The tissues are then irradiated with light of proper wavelength, which induces a photochemical reaction leading to destruction of the malignant tissue. PDT successfully used in treatment of gastrointestinal (GI) tumors was first reported in 1982 by Hayata and Kato. Later the results from a number of studies of the advanced GI tumor were published. In those cases PDT has an actual role for the prolonged survival and the improved quality of life. PDT in early stage of GI carcinoma was recognized as a radical therapeutic method in clinical oncology. Since the normal tissue damage can be minimized, this technique offers the possibility of a safe and effective treatment when other therapeutic modalities either are no longer effective or cannot be performed. The potential efficacy of PDT should be utilized as curative treatment for inoperable early GI cancers.Recently, while the photochemical properties of PDT indicate that singlet oxygen is a primary agent in the induction of tumoricidal effects, the actual, targets of PDT have still not been clearly defined, peveral investigators observed changes in the microcirculation, the presence of a vascular response to PDT is established, but the detailed mechanisms remain the subject of research. Few studies to date have been performed concerning other local ther-...