Three main adverse reactions, namely photosensitivity (reaction that is similar to sunburn), oesophageal stenosis (narrowing or closure of the food pipe), perforation of the treated area (a tear or puncture of the tissue), have been identified in research studies evaluating photodynamic therapy (PDT) with porfimer sodium. Because of the low incidence of the disease or the variation in the occurrence of these adverse reactions among different indications, it is difficult to determine the occurrence and frequency of these safety issues in routine clinical practice.