Background: Bone metastasis in patients with colorectal cancer (CRC) is very rare, and data are extremely lacking. We aimed to evaluate the characteristics of bone metastasis in patients with CRC. Materials and methods: We performed a chart review of 63 patients (1.1 %) with bone metastasis among 5479 patients who underwent surgery for CRC. Results: Most patients were stage 3 (17.5 %) or 4 (73.0 %), and 32 patients (50.8 %) were diagnosed with bone metastasis at initial diagnoses of CRC. Thirty-one patients developed bone metastasis during the follow-up period with median 10.1-month interval. PET-CT was most frequently used for the diagnosis of bone metastasis (71.4 %), and the spine was the most commonly involved site (77.8 %). Most patients had multiple bone metastases (73.0 %) and other metastases (87.3 %). Bone pain was the most common skeletal-related event (25.4 %), and patients were treated with radiation (25.4 %), surgery (14.3 %), or bisphosphonate (6.3 %). The median survival time was 17.8 months, and the 5-year survival rate was 5.7 %. In the multivariate analysis, the risk factors for survival included initial bone metastasis (hazard ratio [HR] 3.03; P < 0.001) and bone metastasis from colon cancer (HR 1.87; P = 0.04). Conclusion: Bone metastasis in patients with CRC is extremely rare and shows poor prognosis.
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