Detection of potentially curable recurrence after colorectal cancer surgery in a real-world population

INTRODUCTION: After curative surgery for colorectal cancer (CRC), patients undergo surveillance because of the risk of recurrence; however, only a subset develops recurrence amenable to further curative-intent treatment. The primary aim of follow‑up is to identify patients with potentially curable recurrence. MATERIALS AND METHODS: A retrospective analysis was performed of stage I-IV CRC patients who underwent curative-intent treatment and entered postoperative surveillance at Isala between 2014 and 2018. Follow‑up was conducted according to Dutch guideline‑based protocols for 60 months. Patients were categorized as having no recurrence, a potentially curable recurrence, or a non-curable recurrence. Prognostic factors at start of follow-up for potentially curable recurrence were assessed using competing‑risk Cox regression, with non-curable recurrence and death as competing events. For patients with recurrence, mode and time of detection were evaluated. RESULTS: During a median follow-up of 60 months, recurrence occurred in 22.4% of 1118 patients. The cumulative incidence function (CIF) of a potentially curable recurrence was 8.0%. Independent variables associated with a potentially curable recurrence were age HR 0.97 (95% CI 0.96-0.99), minor postoperative complications HR 1.78 (95% CI 1.16-2.72), stage III CRC HR2.76 (95% CI 1.19-6.38) and stage IV CRC HR 11.02 (95% CI 4.44-27.37). Among patients with a recurrence, CEA ≥ 5 ng/mL was present in 63% of all recurrences, but less often in the potentially curable group (57% vs. 69%, p = 0.057). Median time to detection of a potentially curable recurrence was 16 months (IQR 20). The overall number needed to follow-up (NNFU) to detect one potentially curable recurrence was 9.8, with the lowest NNFU observed in stage IV CRC (2.3) and in rectal cancer (6.9). CONCLUSION: Standard follow-up enabled the detection of potentially curable recurrence in 8% of CRC patients. The substantial variation in NNFU across subgroups and the limited sensitivity of CEA underscore the need for more personalized, risk‑adapted surveillance strategies.