The effects of photodynamic therapy in upper-gastrointestinal malignant diseases

Abstract

Photodynamic therapy (PDT) is a promising new modality that utilizes the combination of a photosensitizing chemical and visible light for the management of various solid malignancies, including gastrointestinal (GI) cancer. PDT has some advantages over chemotherapy in terms of its greater safety and lower toxicity in the treatment of malignant lesions. However, PDT has not been used widely for treating upper GI cancer due to its relatively low cost-effectiveness and anatomical characteristics of the GI system. Nevertheless, PDT may be an effective alternative therapy for early upper-GI cancer patients who are at a high risk of curative surgical resection or systemic chemotherapy. In some clinical studies, PDT for various upper GI cancer showed positiveresults. To improve the efficacy of PDT for upper GI cancer, development of photosensitezer and light delivery system is needed.

Keywords: Photodynamic therapy; Photosensitizer; Upper-gastrointestinal cancer.

Fig. 1

Energy absorption and excitation: singlet (short-lived) excited-state porphyrin.

Fig. 2

Intersystem crossover (electron spin conversion): internal rearrangement to a longer-lived (triplet-state) porphyrin.

Fig. 3

Production of highly active singlet oxygen.