Clinical landscape of cancer metastases.

Population-based data on metastatic patterns are lacking because cancer registries seldom record metastases. This study uses a novel population-based approach to identify metastases and describes metastatic pathways from 14 common primary cancers to 12 specific metastatic sites. A total of 179 581 patients with metastatic cancer were identified from the Swedish Cancer Registry and metastatic sites were identified using the Cause of Death Register and the National Patient Register. Patterns of metastatic spread were described across age and sex. In men, colorectal cancer was the main source of lung, peritoneal, and liver metastases. Lung cancer was the main origin of pleural and nervous system metastases. Prostate cancer dominated bone metastases but had minor contribution to other metastatic sites. Among women, breast cancer was the dominant origin of most metastatic sites, with the exception of peritoneum which was ruled by metastases from the ovary. As other exceptions, for nervous system metastases, lung cancer was the origin of metastases somewhat more frequently than breast cancer and for liver metastases, colorectal cancer was the main origin instead of breast cancer. The present achievement was to implement the first nationwide description of clinical landscape of cancer metastases, with an aim to serve as a reliable source for clinicians and researchers.