Elimination of the diseased epithelium containing IM with dysplasia is an intuitively favorable step for patients with this diagnosis. In other disease states, such as colon polyps or premalignant skin lesions, removal of the premalignant tissue results in a reduction in the risk of ultimately developing cancer. This is a logical conclusion when considering the premalignant lesion of Barrett's esophagus (particularly Barrett's esophagus with dysplasia), as the "tissue at risk" can be completely removed by ablation. This premise has been tested in the Barrett's dysplasia population in photoablative trials using PDT for patients with HGD, where PDT imparted a 50% reduction in risk over controls for the development of adenocarcinoma (Overholt BF, Panjehpour M, Haydek JM. Photodynamic therapy for Barrett's esophagus: follow-up. Gastrointest Endosc 1999;49(1):1-7.) The AIM Dysplasia Trial primary endpoints are removal of all dysplasia and IM, rather than detection of a difference in progression to adenocarcinoma or higher grades of dysplasia.