Background: Whether metastatic colorectal cancer (mCRC) that presents synchronously with the primary lesion behaves differently from mCRC that appears metachronously to the primary disease is not clear.
Patients and methods: The South Australian Clinical Registry for mCRC collects data for patients diagnosed after February 2006. Data from 2502 patients, available on October 22, 2012, were analyzed according to stage at initial diagnosis (SAID) to compare outcomes between metachronous tumors (MTs) (stages I, II, III) and synchronous tumors (STs) (stage IV). Overall survival (OS) was calculated from the date of mCRC diagnosis.
Results: Patients with ST had more liver-only metastases, and patients with MT had more lung-only, non-lung and non-liver, and non-lung metastases. The median time to recurrence differed significantly according to SAID: stage I, 49.3 mo (n = 29), stage II, 25.2 mo (n = 346) and stage III, 18.4 mo (n = 497). The median OS was longer for patients with MT than for those with ST (19.0 vs.14.9 mo, P = .003). For patients who received any treatment for mCRC, the OS was longer for patients with MT than for those with ST (19.2 vs. 15.3 mo, P = .005). In patients who received only chemotherapy for mCRC, the median OS was longer for patients with MT than for those with ST (15.2 vs. 9.9 mo, P < .0001). No difference in OS between the MT and ST groups for patients who did not receive treatment for mCRC (1.6 vs. 2.6 mo; P = .95).
Conclusion: Patients with MT have a longer OS than those with ST, independent of treatment. Classification of patients according to whether they have metachronous or synchronous presentation of mCRC is prognostic. These results may add further support for population screening with the aim to reduce de novo metastatic disease.
Keywords: Epidemiological; Patterns of metastases; Patterns of treatment; Registry; Survival.
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