Patterns of bone metastases in newly diagnosed colorectal cancer: a real-world analysis in the SEER database.

Purpose: To investigate the incidence and the associated factors for bone metastases (BM) development and prognosis in initial colorectal cancer (CRC) with a large sample using Surveillance, Epidemiology, and End Results (SEER) cohort.

Methods: Primary CRC patients, who were initially diagnosed between 2010 and 2015 in the SEER database, were included to analyze BM incidence and risk factors for BM occurrence. The patients with at least 1-year follow-up were involved to investigate the prognostic factors for BM. Multivariable logistic and proportional hazard regression models were used to investigate the risk factors for BM development and prognosis, respectively.

Results: A total of 212,787 eligible CRC patients were included and 2557 of them were diagnosed with de novo BM (1.20%). Rectal cancer presented significantly higher BM incidence than right and left colon cancer (χ = 107.64, P < 0.001). T1 stage, poor differentiated grade, and brain metastases were homogeneously associated factors for BM development and BM patients' survival. Male gender, higher N stage, rectal site, elevated carcinoembryonic antigen, and lung and liver metastases were positively associated with BM occurrence. Older age, unmarried status, right colon site, and non-surgery were found to positively correlate with the death risk of CRC patients with BM.

Conclusions: BM is rare in CRC patients. Homogeneous and heterogeneous factors were found for BM development and BM patients' survival. The risk factors and prognostic factors can be used for BM screening and patient's prognosis estimation.