OBJECTIVETo investigate the risk factors of metachronous bone metastasis after radical resection of colorectal cancer within 5 years.

METHODSClinical data of 1 749 patients with colorectal cancer, of whom 50(2.8%) patients developed metastasis to bone after operation, in the Department of Colorectal Surgery, Changhai Hospital of The Second Military Medical University from January 2001 to December 2010 were analyzed retrospectively. Univariate and multivariate analysis were performed to find the risk factors of metachronous bone metastasis from colorectal cancer using Chi square test and Logistic regression, respectively.

RESULTSOf 50 colorectal cancer cases with bone metastasis, 29 were male and 21 were female. The age was ≥ 60 years old in 28 cases. Tumors of 36 cases were located in the rectum and of 14 cases located in the colon. Pathology examination showed 43 cases were adenocarcinomas, 7 cases were mucinous adenocarcinoma. Forty-two cases had T3-4 stage lesions, 30 cases had lymph node metastasis, 14 cases had pulmonary metastasis, and 5 cases had liver metastasis. Univariate Chi square test indicated that factors associated with the metachronous bone metastasis of colorectal cancer within 5 years were tumor site (χ=4.932, P=0.026), preoperative carbohydrate antigen 199 (CA199) level (χ=4.266, P=0.039), lymph node metastasis (χ=13.054, P=0.000) and pulmonary metastasis(χ=35.524, P=0.000). The incidence of bone metastasis in patients with rectal cancer (3.6%, 36/991) was higher compared to those with colon cancer (1.8%, 14/758). The incidence of bone metastasis in patients with higher(> 37 kU/L) preoperative serum CA199 level (4.9%, 12/245) was higher compared to those with lower serum CA199 level (2.5%, 38/1504). The incidence of bone metastasis in patients with lymph node metastasis(4.8%,30/627) and pulmonary metastasis (11.6%, 14/121) was significantly higher compared to those without lymph node metastasis (1.8%, 20/1122) and pulmonary metastasis(2.2%, 36/1628), respectively. Logistic multivariate analysis showed that rectal cancer(OR:0.508, 95%CI:0.268 to 0.963, P=0.038), lymph node metastasis (OR:2.291, 95%CI:1.273 to 4.122, P=0.006) and metachronous pulmonary metastasis(OR:4.796, 95%CI:2.473 to 9.301, P=0.000) were the independent risk factors of metachronous bone metastasis of colorectal cancer within 5 years.

CONCLUSIONPatients with rectal cancer, lymph node metastasis and metachronous pulmonary metastasis are high risk groups of metachronous bone metastasis after radical resection of colorectal cancer within 5 years.