Safety of Photodynamic Therapy (PDT) in the Ablation of High-grade Dysplasia (HGD) in Barrett's Esophagus (BE)

Inclusion Criteria:

* Patients are males or females aged 18 or older.
* Patients have been diagnosed with biopsy-proven HGD in BE.
* Non-menopausal or non-surgically sterilized female patients must have a negative serum beta-HCG at the time of entry into the study.
* Non-menopausal or non-surgically sterilized female patients must use a medically acceptable form of birth control.
* Patients must sign an Informed Consent Form, which must comply with the ICH guidelines and local requirements.

Exclusion Criteria:

* Patients who have previously received PDT for HGD in BE.
* Patients who have previously undergone radiation therapy to the chest.
* Patients with known porphyria or known hypersensitivity to porphyrins or any excipients of the porfimer sodium.
* Patients who have esophageal cancer or in whom esophageal cancer, lymph node involvement, or metastases cannot be ruled out based on the pathology report, endoscopic ultrasonography (EUS), computed tomography (CT) scan or other diagnostic methods used in current practice no more than 30 days prior to date of consent.
* Patients with any acute or chronic medical or psychological illnesses as judged clinically significant by the investigator to preclude PDT procedure.
* Patients with a presence or history of neoplasms (treated during the last five years prior to study entry) other than carcinoma in situ of the cervix or basal carcinoma of the skin.
* Patients with esophageal strictures, esophageal diverticula, esophageal or gastric varices.
* Patients with known contraindications to analgesia or endoscopy.
* Patients with blood parameters of Grade 3 or higher on the Common Terminology Criteria for Adverse Events (CTCAE).
* Patients with unstable cardiovascular disease (Class III and IV cardiovascular disease according to the New York Heart Association's functional criteria).
* Patients with esophageal ulcers \> 1 cm in diameter.
* Patients with tracheoesophageal or bronchoesophageal fistula.
* Patients with chronic/acute dermatologic conditions (e.g., urticaria, eczema, sunburn).
* Patients under anticoagulant therapy (only for the subgroup of 12 patients who will consent to provide tissue samples in order to determine the concentrations of oligomers).
* Patients with severe renal or hepatic impairment with parameters of Grade 3 or higher on the CTCAE.
* Patients who have been treated with any investigational drug during 60 days prior to the screening visit.
* Patients who are unable or unwilling to complete the follow-up evaluations required for the study.