EP 648 The Diagnosis of Colorectal Cancer Recurrence Through Carcinoembryonic Antigen Fluctuation After Colorectal Cancer Resection

Abstract Background To describe the changes in carcinoembryonic antigen (CEA) in colorectal cancer recurrence patients. Methods Retrospective data collection of all non-metastatic colorectal cancer resection patients between January 2021 to December 2024 at high-volume, tertiary hospital. Patient demographics, operative, biochemical, and radiological were reviewed. Results 645 patients (366 male, 279 female) were studied, with a median age of 71 (27-90) years. 353 patients were non-smokers, 235 ex-smokers, and 50 patients. 83 patients developed local or metastatic cancer recurrence during the follow-up period; their disease-free survival was 13.7 months. The pre-operative carcinoembryonic antigen level was obtained in 446 patients. It was greater than the normal level of 5ng/mL in 20.90% of this cohort, and ‘normal’, i.e. ≤5ng/mL, in 79.10%. Of the 83 patients with cancer recurrence, 40.26% had an abnormal CEA at the time of recurrence confirmation on imaging, whilst 59.74% had a CEA ≤ 5ng/mL. 16.13% of the 83 patients with a recurrence had an abnormal CEA pre-operatively, whilst a large majority had a normal CEA measurement pre-operatively. The median CEA value at the time of recurrence for the 83 patients was 3.7ng/mL. The median maximum CEA value for the 562 patients without a recurrence was 2.4ng/mL. The median CEA change from baseline (1st CEA post-resection) to CEA at recurrence was 0 and 1.4ng/mL from baseline to maximum CEA. In the non-recurrence group, CEA increased only 0.1ng/mL from baseline to maximum. Conclusion CEA trends can reflect colorectal cancer recurrence, but the degree of change that reflects recurrence needs further research.