Epidemiology and prognosis of synchronous and metachronous colon cancer metastases: a French population-based study.

BACKGROUND

Epidemiological data on synchronous and metachronous metastatic colon cancer are scarce. We assessed epidemiological characteristics and survival in synchronous and metachronous metastatic colon cancer in a French population.

METHODS

Our study included 932 cases of metastatic colon cancer diagnosed in 1999-2010 and registered in a population-based cancer registry; 758 were synchronous colon metastases and 174 metachronous metastases from resected primary colon cancers diagnosed in 1999-2005. Univariate relative survival was calculated and a multivariate model with proportional hazard applied to net survival by interval was used.

RESULTS

Mean age at diagnosis was 71.1 years for patients with metachronous metastasis and 71.4 years for those with synchronous metastasis (p=0.818). Patients with metachronous metastasis were more likely to have R0 resection (Odds Ratio: 3.05 [1.96-4.76], p<0.001) than patients with synchronous metastasis. Five-year relative survival was 7.2% for synchronous metastasis and 17.6% for metachronous metastasis (p<0.001), but did not differ significantly for patients with R0 resection (47.3% and 61.5% respectively, p=0.120). For patients not receiving chemotherapy risk of death was significantly lower in the metachronous metastasis group (Hazard Ratio=0.44 [0.32-0.60], p<0.001).

CONCLUSIONS

On a population basis, synchronous metastasis is an independent poor prognostic factor in colon cancer. Chemotherapy and resection of all metastatic sites significantly improved the outcome in patients with synchronous metastasis.