OBJECTIVE: The aim of this study was to clarify the actuarial incidence of pulmonary metastases and risk factors for pulmonary metastases after curative resection of rectal cancer without preoperative chemoradiotherapy. DESIGN: This study was a retrospective review. PATIENTS: Data for 314 patients who underwent R0 resection for rectal cancer without preoperative chemoradiotherapy from 2000 to 2006 were reviewed. The mean duration of follow-up was 57.0 months. RESULTS: Pulmonary metastases developed in 41 patients. Mean duration from rectal surgery to identification of pulmonary metastases was 21.1 months. Surgery for pulmonary metastases was performed first for 19 patients (46.3%), and all patients achieved R0 surgery. Multivariate analysis revealed that tumor depth (T3 to T4), lymph node ratio (>0.091), and tumor location (anal canal) were significant independent risk factors for pulmonary metastases. Five-year actuarial incidence of pulmonary metastasis increased significantly with increased numbers of risk factors (0 factors, 1.1%; 1 factor, 13.2%; ≥2 factors, 40.1%). In terms of lateral pelvic lymph node involvement, the number of lateral pelvic lymph node involvements (≥4) and the distribution of lateral pelvic lymph node metastases (bilateral) were significant risk factors for pulmonary metastases. CONCLUSIONS: The present study clearly demonstrated predictive factors for pulmonary metastases after R0 resection of rectal cancer without preoperative chemoradiotherapy. Actuarial incidence of pulmonary metastases was significantly related to the number of risk factors present. The data from the present study should facilitate the establishment of novel algorithms for predicting pulmonary metastases after resection of rectal cancer, which may lead to the appropriate surveillance strategies after rectal surgery.
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