Early postoperative PET-CT in patients with pathological stage III colon cancer may change their outcome: Results from a large single-institution study

e15163 Background: Staging of patients (pts) with pathological stage III colon cancer (CC) is currently suboptimal; many pts still recur despite an unremarkable preoperative staging. We previously reported that early postoperative PET-CT can alter the stage and management of up to 15% of pts with high risk stage III CC and later reported also encouraging preliminary results in a larger cohort of consecutive pts with stage III CC, in which staging and management were altered in 14.5%. The aim of the current study was to expand the previous one to a larger cohort and to evaluate the actual impact of early postoperative PET-CT on pts outcome. Methods: A Retrospective study of all consecutive pts with stage III CC who were treated at our institution and underwent early postoperative PET-CT between 2007-2016. Demographic and clinicopathological data were retrieved. Statistical analyses were done using standard methods. Results: 348 pts, 166 (47.7%) males, with a median age of 66 years (range, 29-92), were included. Pathological stage was IIIA, IIIB and IIIC in 21(6%), 254 (73%) and 73 (21%) pts, respectively. The median number of lymph nodes examined and of positive ones were 14 (range, 3-54) and 2 (range, 0-32), respectively. High FDG-uptake was noted in 95 (27.3%) pts, including 23 (6.6%) with clear postoperative changes and 18 (5.2%) with a false positive uptake, of whom 6 underwent invasive diagnostic procedures. PET-CT results modified the management of 52 pts (14.9%) who were found to have true positive findings: 44 (12.6%) with overt metastatic disease and 8 (2.3%) with a second primary tumor. At a median follow-up of 45.6 months, the estimated 5y disease-free survival for true stage III pts was 81.9% and the 6y overall survival of the entire cohort was 76.4%. Interestingly, of the 44 pts found to be metastatic, 12 (27.3%) underwent curative treatments and 8 (66.7%) of those remain free of disease, with a median follow-up of 64.7 months. Conclusions: In this large cohort, early postoperative PET-CT changed the staging and management of 14.9% of pts with resected stage III CC, with encouraging outcome results. We are conducting a prospective trial to further evaluate this strategy.