Abstract: Nine selected patients with rectal tubulo-villous adenomas were treated with Photofrin- or aminolevulinic acid (ALA)-based photodynamic therapy (PDT) after the main bulk of the primary tumors had been endoscopically resected. The distribution patterns of Photofrin and ALA-induced porphyrins in the adenomas and surrounding normal tissues were studied by means of microscopic fluorescence photometry. Nine patients were treated in a total of 14 PDT sessions. Photofrin and ALA were used in 5 and 9 sessions, respectively. The tumors in all 5 Photofrin-based PDT sessions demonstrated complete regression. However, they all recurred 4 - 20 months after PDT. Four of 9 ALA-based PDT sessions achieved complete regression and so far no recurrence of these tumors has been found, although the follow-up is only 3 - 10 months. Two of the cases of partial response were given a second ALA-based PDT and both of them obtained complete response. The microscopic fluorescence photometry of the biopsies taken from the tumor and surrounding normal tissues after administration of either Photofrin or ALA showed that there was a strong fluorescence of Photofrin in the vascular stroma of the tumor and normal tissues, whereas ALA-induced porphyrins were mainly distributed in the glandular neoplastic cells. The correlation between the distribution of Photofrin and ALA-induced porphyrins in the adenomas and their photodynamic effects is discussed. !34
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