Patterns of venous thromboembolism risk in patients with localized colorectal cancer undergoing adjuvant chemotherapy or active surveillance: an observational cohort study.

BACKGROUND: Venous thromoboembolism (VTE) is a frequent and burdensome complication of metastatic colorectal cancer (CRC). However, the epidemiology of VTE in patients with localized CRC after surgery in curative intent is incompletely understood. In this single-center observational cohort study, we investigate patterns of VTE risk in localized CRC, and define its relationship with baseline risk factors, adjuvant chemotherapy and CRC recurrence.

METHODS: Five-hundred-sixteen patients with stage II/III CRC were included retrospectively at the time of surgery, and followed until the occurrence of VTE, CRC recurrence, or death (median age = 65.1 years, stage II and III: n = 151 (29.5%), n = 361 (70.5%); adjCTX: n = 339 (65.7%)).

RESULTS: During a median follow-up of 2.7 years, 15 VTEs (2.7%) and 116 recurrences (22.5%) occurred, and 46 patients (8.9%) died. Six-month, 1-year, and 5-year VTE risks were 1.6%, 2.0% and 3.2%, respectively. In competing risk time-to-VTE regression, adjCTX was not associated with an increased risk of VTE (Subdistribution hazard ratio = 0.98, 95% CI:0.33-2.88, p = 0.97). The occurrence of disease recurrence strongly increased the risk of VTE (Multi-state model: Transition hazard ratio (THR) = 13.03, 95% CI:4.39-38.74, p < 0.0001)). Conversely, the onset of VTE did not predict for recurrence (THR = 1.95, 95% CI: 0.62-6.16, p = 0.25).

CONCLUSION: VTE risk is very low in localized CRC and does not appear to be increased by adjuvant chemotherapy. Thus, primary thromboprophylaxis is unlikely to result in clinical benefit in this population. The strongest determinant of VTE risk appears to be disease recurrence.