The utility of surveillance CT scans in a cohort of survivors of colorectal cancer

Purpose: Colorectal cancer (CRC) is the third most common cancer worldwide. After curative intent treatment, international guidelines recommend surveillance protocols which include annual CT chest, abdomen and pelvis (CAP) and serum carcinoembryonic antigen (CEA) monitoring which aim to improve overall survival by early detection of recurrence. Despite the widespread recommendations, robust evidence of an overall survival benefit is lacking. Our study aimed to quantify the utility of annual CT CAP as a surveillance modality in comparison to the rate of potentially harmful false-positive and incidental findings.

Methods: High-risk stage II and stage III CRC patients were retrospectively identified from the Sydney Cancer Survivorship Centre database. Findings on surveillance CT were classified into confirmed recurrence or the potentially harmful findings of (a) false-positive or (b) clinically significant incidental finding.

Results: A total of 376 surveillance CT CAPs were performed in 174 survivors between 12 September 2013 and 30 June 2020. The recurrence rate during the study period was 23/174 (13.2%) with the majority of recurrences detected by abnormal CEA (14/23, 60.9%) versus surveillance CT (4/23, 17.4%), with the remainder identified on non-surveillance CT (5/23, 21.7%). Curative intent surgery was performed in 12/23 people with CRC recurrence. Surveillance CT was shown to result in high levels of false-positive (31/174, 17.8% of patients) or clinically significant incidental findings (30/174, 17.2% of patients). The risk of identifying these potentially harmful findings was ongoing with each year of surveillance CT.

Conclusion: Surveillance CT was associated with low detection rates and high rates of potentially harmful findings bringing this surveillance modality under further scrutiny.

Implications for cancer survivors: An increased emphasis should be placed on educating survivors on the benefits of surveillance CT weighed against the risk of potentially harmful findings.