“…4,10,14,27,[39][40][41] Studies designed to identify mechanisms of false-positive and false-negative results have shown effects from differences in the levels of tumor cell metabolism, intraoperative microscope sensitivity, 5-ALA uptake, 5-ALA metabolism (resulting from intrinsic molecular characteristics of the tumor and/or interactions with other therapies), diffusion of protoporphyrin IX, and other factors. 4,8,16,23,27,29,36,[40][41][42] Despite these caveats, the improved patient outcomes reported after use of 5-ALA underscore the utility of tumor markers that can be used intraoperatively to improve tumor cell identification and facilitate more complete resections.…”