This SBIR Phase II project aims to develop a commercial grade optical probe and system for FDA clinical trials and subsequent commercialization of a population-wide colon cancer screening test. An interdisciplinary research team of engineers, biologists, and clinicians has developed low-coherence enhanced backscattering (LEBS), an optical technique which enables sensing tissue microarchitectural correlates of the genetic/epigenetic changes in otherwise histopathologically normal mucosa. The preliminary animal and human studies demonstrated the potential of LEBS to detect subtle alterations in histologically normal-appearing tissue that occur with the presence of precancer in a different part of an organ, a consequence of the well-established concept of field carcinogenesis. This opens a possibility to detect colonic adenomas by means of LEBS analysis of rectal tissue, which is readily accessible using a rectal probe and without the need for colonoscopy or bowel preparation. Indeed, ex vivo human studies and a small-scale trial of the in vivo LEBS probe from Phase I research demonstrate that rectal LEBS is remarkably accurate for predicting neoplasia anywhere in the colon. In continued close collaboration with the research team, American BioOptics endeavors in Phase II to refine the prototype LEBS probe into a medical-grade probe for use in a patient without bowel preparation and to develop a low-cost LEBS optical system for multi-center FDA trials and subsequent commercialization. LEBS has the potential to become the first truly population-wide test for colon cancer screening performed during an annual exam by a primary care physician, without colonoscopy or bowel preparation to determine the need for colonoscopy. The proposed test would be simple, inexpensive, minimally intrusive and highly accurate without the need for bowel cleansing. Colon cancer is the second leading cause of cancer deaths in the U.S. largely because of especially poor screening participation relative to other major cancers. Only a small fraction of eligible population (90 million Americans over age 50) undergoes screening colonoscopy due to a variety of reasons including expense, patient reluctance, complications, and insufficient number of endoscopists. Development of a minimally invasive test to identify patients who do and do not harbor colonic adenomas is of crucial importance to enable, for the first time, population-wide screening for this disease. Currently, no such initial screening test is available. Based on the results of the LEBS test, the physician could recommend either no colonoscopy (the majority of cases) or need for colonoscopy (which the patient will be more compliant with). Thus, with a readily available LEBS screening test developed in Phase II and subsequent FDA approval, more patients with colonic neoplasia will undergo colonoscopy. The LEBS test would not only prevent many more colon cancer deaths by screening a larger part of the population, but it would also reduce costs/complications of screening in the majority of the population who are not destined to develop neoplasia