Early colorectal cancer detection on routine CT to improve patient's 5-year survival.

Abstract

593 Background: Prognosis of colorectal cancer (CRC) is greatly influenced by stage at diagnosis. Early colorectal cancer can be subtle on CT scans showing only mild wall thickening, small polyps, or subtle lymph nodes. Identifying these lesions on CT performed for nonspecific symptoms can help identify interval CRC and improve patient outcome. The purpose of the present study is to classify missed CRC on abdominal CT by their imaging features and whether early identification can downstage CRC patients. Methods: A retrospective analysis was conducted of patients (pts) diagnosed with CRC. Data collection included age, gender, ECOG, KRAS mutation status, overall survival (OS). CT obtained prior to and at diagnosis were evaluated. Images were reviewed for multiple CT features including appearance of mass, mesenteric infiltration, abnormal draining lymph nodes, contrast enhancement relative to adjacent mucosa, and intralesional calcifications. Staging was evaluated using available CT scan and based on the TNM staging system for CRC. Results: The 41 pts with 51 prediagnostic CTs from 1/1/2012 - 12/31/2015 had mean age of 68 years (range:44-90 ) Mean ECOG status for the population was 1.46. 41% of the prediagnostic CTs had missed findings. 52 and 43 % of the missed findings were in the rectosigmoid and ascending colon respectively. Of the 15 missed masses, 9 appeared as asymmetric wall thickening, 3 as concentric wall thickening, and 3 as polyps. Of the 14 missed lymph node groups, 2 were excluded due to stability or nonrelated condition. The remaining lymph nodes were found in the associated draining station and averaged 3±1.2 mm in size. On average, the stage at prediagnostic CT was 3A and the diagnostic CT was 3C (p = 0.0015). Average time lapse between prediagnostic and diagnostic CT was 21 months (3-64 months). Conclusions: High percentage of CRC findings are missed on abdominal CT due to their subtle feature, with most misses in the rectosigmoid and ascending colon. A dedicated search can improve detection by specifically looking for polyps, wall thickening, and small lymph nodes in the draining station. Early detection of CRC can improve survival by lowering the stage from 3C to 3A, thus providing 36% improvement in 5-year survival.