All patients will receive one course of PDT consisting of an intravenous injection of 2.0 mg/kg of porfimer sodium over 3-5 minutes followed by one or two endoscopic laser light applications. The first laser light application will be performed within 40-50 hours using a new diffusing balloon catheter. The second laser light application (without a diffusing balloon catheter) will be performed within 96-120 hours on those areas showing an insufficient response to the first application. Follow-ups (Weeks 4 and 13) will include some or all of the following procedures: physical exam; vital signs evaluation; body weight; endoscopy; skin, degree of difficulty in swallowing and esophageal stenosis assessment; and clinical laboratory check. All patients will be asked general open questions about any occurrence of adverse events, change in concurrent medical conditions, use of adjunctive therapy/procedure, and intake of concomitant medication. All patients will undergo rigorous systematic endoscopic biopsy surveillance at Week 13 (final visit).