Objective: This study aimed to determine the relationship between the tumor load and carcinoembryonic antigen (CEA) positivity by comparing CEA positivity and volume-based positron emission tomography/computed tomography (PET/CT) preoperative parameters in patients with colorectal cancer.

Methods: This retrospective study included a total of 87 patients with colorectal cancer who underwent PET/CT between January 2018 and December 2019 and had simultaneous CEA measurements. CEA level ≥5 ng/mL was accepted as positive. Patients who underwent surgery or received chemotherapy/radiotherapy were excluded from the study. The maximum standardized uptake value (SUVmax), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) values were calculated using 18fluoro-fluorodeoxyglucose PET/CT images of the patients.

Results: CEA was positive in 43 (49.4%) patients. The site of the primary lesion was the rectum in 40 (46%) patients, sigmoid colon in 19 (21.8%), ascending colon in 14 (16.1%), descending colon in 9 (10.3%), transverse colon in 3 (3.4%), hepatic flexure in 1 (1.1%), and descending-sigmoid colon junction in 1 (1.1%). No significant association was noted between the intestinal segment of the primary lesion and CEA positivity (p=0.878). Moreover, no significant difference was found among SUVmax, MTV, and TLG values of the primary tumor and CEA positivity (p=0.611, p=0.980, and p=0.527, respectively).

Conclusion: Preoperatively, no significant relationship was found between CEA positivity and volume-based PET/CT parameters, specifically MTV and TLG, in patients with colon cancer. CEA positivity in the preoperative period has low diagnostic effectiveness independent of the tumor load.