Background: Synchronous metastases of colorectal cancer (CRC) are considered to be of worse prognostic value compared with metachronous metastases, but only few and conflicting data have been reported on this issue.
Methods: We retrospectively investigated patient demographics, primary tumour characteristics and overall survival (OS) in 550 advanced CRC patients with metachronous vs synchronous metastases, who participated in the phase III CAIRO study. For this purpose only patients with a prior resection of the primary tumour were considered.
Results: The clinical and pathological characteristics associated with poor prognosis that we observed more often in patients with synchronous metastases (n=280) concerned an abnormal serum lactate dehydrogenase (LDH) concentration (P=0.01), a worse WHO performance status (P=0.02), primary tumour localisation in the colon (P=0.002) and a higher T stage (P=0.0006). No significant difference in median OS was observed between patients with synchronous metastases and metachronous metastases (17.6 vs 18.5 months, respectively, P=0.24).
Conclusion: Despite unfavourable clinicopathological features in patients with synchronous metastases with a resected primary tumour compared to patients with metachronous metastases, no difference in the median OS was observed. Possible explanations include a (partial) chemoresistance in patients with metachronous disease because of previous adjuvant treatment, whereas differences between the two groups in screening procedures resulting in a lead time bias to diagnosis or in prognostic molecular markers remain speculative.