Abstract
Photodynamic therapy (PDT) is based on the theoretical principle: the specific low level laser light irradiation activates a photosensitizer which is selectively concentrated in rapidly proliferating tissues including malignant tumor cells, resulting in selective necrosis by the intracellular singlet oxygen from photochemical reaction. PDT using Photofrin® (porfimer sodium) with excimer-dye laser (EDL) was approved in Japan. Its indication for GI cancers was limited to superficial esophageal and early gastric cancer not indicated for other curative treatments. Meanwhile, endoscopic mucosal resection (EMR) is considered the first choice of treatment for intra-mucosal GI cancers. Thus PDT has been considered as one of the alternative treatments for GI cancers including recurrent cancer; however, its efficacy was relatively limited. Therefore, we have designed a new therapy called "Modified PDT". The major points of Modified PDT are as follows. 1. Irradiation of EDL is applied to the lesion not only 48 but also 72 hours after Photofrin® injection. 2. When the cancer is polypoid type, partial resection of the cancer is performed before irradiation. 3. Before the second irradiation, necrotic tissue covering the surface of the lesion is removed. Modified PDT was carried out on 20 patients (mean age 73 years). Complete response was achieved in 4 of 6 (66.7%) of superficial esophageal cancers, 9 of 10 (90%) of early gastric cancers, 1 of 3 (33.3%) of advanced gastric cancers and 1 rectal cancer. No serious complication occurred. Modified PDT may be considered an alternative therapy for GI cancers not indicated for EMR or surgery.
