Tumor location is an independent predictive factor for distant metastasis and metastatic sites of rectal adenocarcinoma in patients receiving total mesorectal excision

Background and Objectives: To evaluate the predictive factor for and patterns of distant metastasis in patients with rectal adenocarcinoma receiving total mesorectal excision (TME). Methods: We enrolled 217 consecutive patients who had histologically confirmed rectal adenocarcinoma and underwent surgery at Taipei Medical University- Wanfang Hospital between January 2000 and December 2014. TME was performed in all patients undergoing a sphincter-sparing procedure or abdominal perineal resection of rectal cancer. We performed univariate and multivariate Cox regression analyses of the distant metastasis rate in all patients to evaluate predictive factors. Overall survival (OS) rates were calculated using the Kaplan-Meier method, and Kaplan-Meier survival curves were compared using the log-rank test. Results: A multivariate Cox regression analysis of the distant metastasis rate in patients with rectal adenocarcinoma identified tumor locations and American Joint Committee on Cancer (AJCC) stages as prognostic risk factors. The adjusted hazard ratios (aHRs) of distant metastasis for the upper-third, middle-third, and AJCC stage I-II cancers were 0.08 (95% CI, 0.01-0.69; p = 0.021), 0.41 (95% CI, 0.15-0.99; p = 0.047), and 0.20 (95% CI, 0.10-0.66; p = 0.008), respectively. The 5-year lung metastasis rates among patients with upper-, middle-, and lower-third rectal cancers were 0%, 3.37%, and 13.33%, respectively (log-rank, p = 0.001), and the 5-year liver metastasis rates among patients with upper-, middle-, and lower-third rectal cancers were 2.12%, 9.10%, and 11.76%, respectively (log-rank, p = 0.096). The 5-year OS rates also differed with different rectal adenocarcinoma locations. The 5-year OS rates for upper, middle, and lower rectal cancers were 96%, 86%, and 64%, respectively (log-rank, p < 0.001). Conclusion: A poor OS rate and high lung or liver metastasis rate were observed in distal rectal adenocarcinoma. Longer intensive surveillance of the chest, abdomen, and pelvis after TME in distal rectal adenocarcinoma could be necessary.