Photodynamic therapy (PDT) uses a combination of a drug, porfimer sodium, and a light from a non heated laser. The activation of the drug is done by lighting of abnormal areas using a fiber optic device. The fiber optic device is a very fine fiber (like a fishing line) that permits transmission of light. The fiber optic device is inserted into a diffusing balloon device to ensure the good positioning of the fiber optic within the esophagus (food pipe). It is thought that the size and the flexibility of a new diffusing balloon device could improve the safety profile of the photodynamic treatment by reducing the risk of narrowing or closure of the food pipe (esophageal stenosis) sometimes occurring after treatment.