OBJECTIVETo investigate the factors in the disease-free interval (DFI) of metachronous pulmonary metastasis from rectal cancer.

METHODSClinical data of 92 patients with metachronous pulmonary metastasis from rectal cancer in the Department of Colorectal Surgery at the Changhai Hospital of the Second Military Medical University from January 2001 to December 2013 were analyzed retrospectively. Univariate and multivariate analysis were performed to find the factors affecting disease-free interval of metachronous pulmonary metastasis from rectal cancer using Log-rank test and Cox proportional hazards model, respectively.

RESULTSThe median age of all the cases was 61 (range, 26-81) years. Of the 92 cases, 59 were males and 33 were females. Thirty-six cases were confirmed to have <5 cm distance from lower margin to dentate line. Forty-four cases were examined to have 5 μg/L carcinoembryonic antigen(CEA) level. Of these cases reviewed pathologically, 69 cases were adenocarcinoma, 23 were mucinous adenocarcinoma; 19 cases had stage T1-2 lesions, 73 had stage T3-4 lesions; 43 cases had stage N0 metastasis, 49 had stage N1-2 metastasis. Thirty cases received preoperative radiotherapy, 63 cases received postoperative chemotherapy. The median follow up time of all the cases was 62(range, 3-140) months. The DFI of all the cases was (25.9±21.0) months. Univariate Log-rank test indicated that the factors associated with the disease-free interval of metachronous pulmonary metastasis of rectal cancer were location of the tumor(χ(2)=4.496, P=0.034), preoperative CEA level (χ(2)=5.553, P=0.018), T stage (χ(2)=5.796, P=0.016), N stage (χ(2)=6.780, P=0.009), preoperative neoadjuvant radiotherapy (χ(2)=11.718, P=0.001) and postoperative adjuvant chemotherapy (χ(2)=9.214, P=0.002). A shorter distance from lower margin to dentate line(<5 cm), a lower preoperative CEA level(<5 μg/L), advanced T stage lesions(T3-4), advanced N stage metastasis(N1-2), no use of preoperative radiotherapy and use of postoperative chemotherapy were associated with shorter DFI of patients with metachronous pulmonary metastasis from rectal cancer. Multivariate analysis showed that N stage(OR=0.525, 95% CI: 0.309-0.891, P=0.017), location of the tumor (OR=1.770, 95% CI:1.115-2.812, P=0.016) and preoperative neoadjuvant radiotherapy (OR=1.976, 95% CI:1.228-3.401, P=0.006) were the independent risk factors associated with the disease-free interval of metachronous pulmonary metastasis from rectal cancer.

CONCLUSIONSAdvanced N stage, low location of the tumor and no use of preoperative neoadjuvant radiotherapy are risk factors of shorter disease-free interval of metachronous pulmonary metastasis from rectal cancer.