Photodynamic therapy in the esophagus

Abstract

Photodynamic therapy (PDT) involves in situ photo-activation of photosensitizers by light at appropriate wavelength, generating highly active singlet oxygen and free radicals. For esophageal mucosal dysplasia such as high-grade dysplasia or intramucosal cancer, curative endoluminal therapy including PDT is now a reality. We review the role of PDT in the esophagus for the past two decades. The light for PDT can be delivered endoluminally freehand by cylindrical diffusers, via inflatable balloon stabilizers or microlens fibers. Porfimer sodium (Photofrin ®) is the only approved photosensitizer for PDT in the esophagus in North America, Europe and Japan. In addition, 5-aminolaevulinic acid (ALA), m-tetra(hydroxyphenyl)chlorin ( m-THPC) and benzoporphyrin derivative monoacid ring A (BPD-MA) are other photosensitizers are being evaluated. More randomized clinical trials with long term follow up data are needed to further establish the role of PDT and other endoluminal ablative therapies either on their own or in combination to demonstrate survival benefits, quality of life advantages and cost-effectiveness. Changes in light delivery, timing, dosimetry and new endoscopic devices are needed to possibly improve all aspects of effectiveness. PDT was used mainly for palliation of advanced obstructing cancer of the esophagus at the gastrointestinal junction. More recently, because of the rising detection of the high-grade dysplasia in Barrett’s esophagus, a curative role of PDT in being realized.