Photodynamic therapy and neoplastic disease.

The selective photosensitization of neoplastic lesions is a new modality for eradication of early tumors and palliation of more advanced disease. There is a substantial amount of information relating to modes of photodamage, and the clinical role of this form of therapy is becoming clarified. New sensitizers are being developed with a view toward an enhanced photodynamic effect, utilization of simpler light sources, and elimination of concurrent skin photosensitization. The mechanism whereby efficacious photosensitizers localize in neoplastic, as compared with normal, adjacent tissue remains to be determined, although theories have been proposed. The photosensitizing agent used in most clinical protocols in Photofrin. This product is a complex mixture of porphyrin monomers, dimers, and higher oligomers, and interpretation of biologic and photophysical data is often difficult, although this is not universally appreciated.