Successful Destruction of Human Gastrointestinal Carcinomas in Thymusaplastic Nude Mice After Photodyamic Therapy

Photodynamic therapy (PDT) is a new promising method for the local destruction of tumours. It is based on the following theoretical principle: Dihematoporphyrinether/ester, a photodynamic agent, is retained longer and in higher concentrations in tumours than in their surrounding normal tissue. When activated with light, a local cytotoxic effect is produced that is thought to be mediated via singlet oxygen [1]. The primary target of the PDT is, although the mechanism is still unclear, the vascular endothelium of the neoplastic tissue [2]. Although preliminary reports have been published describing PDT of human gastrointestinal carcinomas [3,4], no tumor-specific experimental data are available on the relationship between the energy density applied and tumor destruction.