PHOTODYNAMIC THERAPY FOR GASTROINTESTINAL TUMORS USING 3 PHOTOSENSITIZERS - ALA INDUCED PPIX, PHOTOFRIN(R) AND MTHPC - A PILOT-STUDY

Photodynamic therapy (PDT) produces localized necrosis with light afte r prior administration of a photosensitizing drug. As PDT lesions in t he gastrointestinal tract heal well, the technique is suitable for rep eated endoscopic use. In this study we used PDT to treat benign and ma lignant gastrointestinal tumors in esophagus, duodenum and rectum in 2 2 patients, who refused or were not suitable for surgery. Patients wer e sensitized with 0.15 mg/kg of body weight with mesotetrahydroxypheny lchlorin i.v. m-THPc (2 patients), with 2.0 mg/kg Photofrin(R) i.v. (4 patients) or 60 mg/kg 5-aminolevulinic acid orally ALA (which is conv erted in vivo to active derivate protoporphyrin TX -PPIX) in fractiona ted doses (16 patients). Laser treatment was performed 2 days after Ph otofrin(R), 2 and 4 days after mTHPc and 4 hours after ALA, using a me tal vapour laser (628 nm, 50-150 J/cm(2) for ALA and Photofrin(R), 650 nm and 10-15 J/cm2 for mTHPc). Using ALA, the necrosis was only super ficial (up to 1.8 mm depth). Four patients treated with Photofrin(R) s howed deeper necrosis, in one case of 8 mm colon cancer complete respo nse, in three cases 1-1.5 cm adenomatous polyps involving the ampulla Vateri 50% longer term reduction in size - seen endoscopically. Two pa tients with rectal villous adenomas treated with mTHPc showed 60-80% r eduction in size (observed endoscopically) within few days after PDT, with better effects for treatment carried out 4 rather than 2 days aft er the sensitization. In all patients the healing was without any comp lications. Photofrin(R) and mTHPc work better, but cause cutaneous pho tosensitivity lasting 12 and 5 weeks, respectively. Better results wit h ALA are possible when using higher drug doses or modified light dosi metry. PDT is a promising treatment for small localized turners in pat ients unsuitable for surgery, but further work is required to optimize the treatment conditions.