Background: Patients who relapse after potentially curative surgery for colorectal cancer tend to relapse within 5 years. There is, however, a group of patients who relapse beyond 5 years after resection and this late relapsing group may have a different behaviour and prognosis.
Methods: We analysed data from a prospective population-based registry to compare the characteristics and survival of relapsed patients with metachronous mCRC. Patients were categorised into relapse at <2, 2-5 and >5 years following their initial surgery. Univariate log-rank tests and multivariate Cox regression was performed to determine whether time to relapse (TTR) and other factors were associated with overall survival (OS).
Results: A total of 750 metachronous mCRC patients were identified. In all, 56% relapsed ≤2 years, 32.4% at 2-5 years and 11.6% >5 years. Median survival time from the time of diagnosis of mCRC for the three groups was 17.6, 26.1 and 27.5 months, respectively. Short TTR (<2 years) was significantly associated with survival (HR=0.75, 95% confidence interval (CI)=0.60-0.93 and HR=0.73, 95% CI=0.53-1.01, respectively, for 2-5 and >5 years vs <2 years, P<0.05). However, there was no significant difference in survival between patients who relapsed at 5 years or later compared with those who relapsed between 2 and 5 years (HR=0.98, 95% CI=0.69-1.38, P=0.90).
Conclusion: TTR within 2 years is an independent predictor of shorter survival time for mCRC patients who experience a relapse. These data do not support the hypothesis that patients who have late relapse late (>5 years) have a 'better' biology or survival compared with patients with a TTR of 2-5 years.