ABSTRACT
BACKGROUNDS: Clinicopathologic factors relating to developing metachronous colorectal cancer (CRC) have been reported. However, the effects of different diagnostic intervals on these risk factors required further analysis. PATIENTS AND METHODS: This retrospective study comprised 14,481 patients diagnosed from January 1995 to December 2012. Metachronous CRC was defined as the occurrence of a second colorectal cancer at least 1 year post-operatively. RESULTS: A total of 153 (1.06%) patients developed metachronous CRCs during the follow-up. Significantly higher rates of developing metachronous cancer occurred in male patients (1.2 vs 0.9%), patients with synchronous CRC (2.0 vs 1.0%), and patients with a positive family history of CRC (1.4 vs 0.9%). Pertaining to diagnostic intervals related to clinicopathological features, more severe staging was significant in the diagnostic interval between 2 and 3 years (35 vs 7.7%, 20.6%, 17.5%, P = .01) compared with other intervals. Male patients were more frequently detected to have CRC within 3 years compared with females (53.1 vs 29.1%, P = .005). For a diagnostic interval ⧠5 years, a significantly higher rate of metachronous CRC located at the right colon was observed than that located at the left colon (36.6 vs 19.7%, p = 0.03). CONCLUSIONS: We evinced that a diagnostic interval between 2 and 3 years was a key time for metachronous CRC diagnosis with worse staging distribution. Based on current findings, we recommend the stratification of metachronous CRCs into diagnostic intervals of 1-2, 2-3, and ⧠3 years, as they exhibit significantly different characteristics.