Carcinoembryonic antigen directed PET-CECT scanning for postoperative surveillance of colorectal cancer

Abstract

Aim: During the follow-up of surgically resected colorectal cancer (CRC), positron emission tomography-contrast-enhanced computed tomography (PET-CECT) is indicated for asymptomatic elevation of carcinoembryonic antigen (CEA) > 5 ng/ml and no obvious site of recurrence on clinical examination and basic imaging. As an institutional policy, a PET-CECT scan was performed at our institute whenever (1) CEA levels rose above 5 ng/ml and (2) CEA values were doubled (even if the CEA level was < 5 ng/ml). Our aim was to correlate the range of CEA elevation with recurrence rates and to evaluate the diagnostic utility of PET-CECT scanning in this setting.

Method: We retrospectively analysed all cases where a PET-CECT scan was performed for elevated CEA levels during surveillance visits after complete resection of the primary tumour followed by adjuvant therapy. This study was conducted from 1 January 2013 to 31 July 2015.

Results: In all, 104 patients underwent a PET-CECT scan for rising CEA values, and 62 patients (59.6%) were found to have recurrent disease. At CEA levels < 5, 5.1-10, 10.1-15, 15.1-50 and > 50 ng/ml, disease recurred in 10%, 45%, 70%, 94% and 100% patients, respectively. Sensitivity, specificity, positive predictive value and negative predictive value of the PET-CECT scan were 92.7%, 95.2%, 96.2% and 90.9%, respectively. Elevation of CEA levels during follow-up was indicative of recurrence in 68% of the secretors and 45% of the non-secretors (based on baseline CEA status).

Conclusion: In the setting of rising CEA levels during follow-up of patients with CRC, a PET-CECT scan is a valuable tool to detect recurrence, irrespective of the baseline CEA secretor status. The likelihood of recurrence of disease was directly proportional to the value of the raised CEA level.

Keywords: Colorectal cancer; carcinoembryonic antigen; positron emission tomography; secretor status; surveillance.