BACKGROUND

Population-based data on the incidence of frequent colorectal metastases are fairly scarce, while that on rare metastatic sites are lacking.

AIMS

The aim of this study was to provide epidemiological indicators of metastatic sites frequency in patients with colorectal cancer.

METHODS

Incidence was modelled using Poisson and Joinpoint regressions in a population-based cancer registry study including metastatic colorectal cancers diagnosed between 1991 and 2020 (N = 5,199). Tumor molecular markers were collected for the [2016-2020] period.

RESULTS

Liver, peritoneum, lung and bone were the most frequent metastatic sites. Among frequent sites, incidence of liver and lung sites decreased in men respectively since 1999 and 2010, whereas in women incidence of liver and peritoneum sites increased steadily throughout the whole period. Each of the other sites concerned less than 3% of metastatic colorectal cancer cases and presented standardized incidence rates between 0.19 and 1.39 per 1,000,000. Among rare sites, incidence of adrenal glands, supraclavicular lymph node, mediastinum and ascites had doubled in [2016-2020] as compared to the 25 previous years. BRAFV600E variant was more frequent in presence of carcinomatosis, and absence of liver and lung metastasis while KRAS variant was more frequent in presence of lung metastasis.

CONCLUSION

This study provides unprecedented incidence indicators for rare synchronous metastases of colorectal cancer.