PHOTODYNAMIC THERAPY FOR POLYPS IN FAMILIAL ADENOMATOUS POLYPOSIS - APILOT-STUDY

Photodynamic therapy (PDT) produces localised necrosis with light afte r prior administration of a photosensitising drug. As PDT lesions in t he gastrointestinal tract heal so well, the technique is suitable for repeated endoscopic use. In this study, PDT was used to treat large po lyps (four duodenal and two colorectal) unsuitable for surgery in 6 pa tients with familial adenomatous polyposis (FAP). Patients were sensit ised with 60 mg/kg 5-aminolaevulinic acid (ALA) orally or intravenous (i.v.) 2.0 mg/kg Photofrin. Laser treatment was performed 6 h after AL A or 48 h after Photofrin using a gold vapour laser. Necrosis was only superficial (up to 1.8 mm) using ALA but much deeper using Photofrin. The one malignant polyp (8 mm diameter in the colon) showed a complet e response using Photofrin. All healed safely with no complications. P hotofrin worked better, but caused cutaneous photosensitivity lasting up to 3 months. ALA cleared within 2 days, but its use is limited by t he superficial effect. Better results with ALA may be obtained using h igher drug doses or modified light dosimetry. Fluorescence microscopy showed no evidence of selectivity of photosensitisation between neopla stic and normal tissue. PDT is a promising treatment for inoperable po lyps in patients with FAP, but further work is required to optimise th e treatment conditions.