Photodynamic therapy for polyps in familial adenomatous polyposis--a pilot study

Photodynamic therapy (PDT) produces localised necrosis with light after prior administration of a photosensitising drug. As PDT lesions in the gastrointestinal tract heal so well, the technique is suitable for repeated endoscopic use. In this study, PDT was used to treat large polyps (four duodenal and two colorectal) unsuitable for surgery in 6 patients with familial adenomatous polyposis (FAP). Patients were sensitised 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 ALA 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 complete response using Photofrin. All healed safely with no complications. Photofrin worked better, but caused cutaneous photosensitivity lasting up to 3 months. ALA cleared within 2 days, but its use is limited by the superficial effect. Better results with ALA may be obtained using higher drug doses or modified light dosimetry. Fluorescence microscopy showed no evidence of selectivity of photosensitisation between neoplastic and normal tissue. PDT is a promising treatment for inoperable polyps in patients with FAP, but further work is required to optimise the treatment conditions.