Patienter blev udelukket fra undersøgelsen, hvis der forekom invasiv øsofaguscancer, hvis de havde cancer i sygehistorien udover ikke- melanomisk hudcancer, eller hvis de tidligere havde fået PDT på øsofagus.
Patients were excluded from the study if there was a presence of invasive oesophageal cancer, if they had a history of cancer other than non- melanoma skin cancer or if they had received prior PDT to the oesophagus.