A critical reappraisal for the value of tumor size as a prognostic variable in rectal adenocarcinoma

Background and Objectives: To investigate critical prognostic factors for local recurrence in patients with rectal adenocarcinoma. Methods: We enrolled 221 consecutive patients who had histologically confirmed adenocarcinoma of the rectum and underwent surgery in our hospital between January 2000 and December 2014. Total mesorectal excision was performed in all patients undergoing a sphincter-sparing procedure or abdominal perineal resection of rectal cancer. To evaluate prognostic factors for local recurrence, we performed univariate and multivariate Cox regression analyses of the local recurrence rate in all patients. Overall survival rates were calculated using the Kaplan-Meier method, and Kaplan-Meier survival curves were compared using the log-rank test. Results: After the inclusion of only model variables of local recurrence with the highest or lowest univariate risk, a tumor size of <5 cm, a negative circumferential margin, well-to-moderately differentiated adenocarcinoma, low anterior resection, not receiving adjuvant RT, pathological T1-T3 stages, and upper- and middle-third rectal cancers were identified as strong prognostic factors with hazard ratios of 0.18, 0.20, 0.03, 0.01, 0.25, 0.18 and 0.18, respectively (95% confidence intervals [CIs], 0.06-0.58, 0.05-0.82, 0.03-0.38, 0.04-0.23, 0.05-0.64,0.09-0.70 and 0.06-0.54, respectively). After the multivariate Cox regression analysis of the local recurrence rate, a pathological tumor size of ≥5 cm was identified as the only prognostic risk factor (95% CI, 0.03-0.66; P = 0.013). The 5-year local recurrence rates among the patients having tumors measuring <5 cm and ≥5 cm in size were 1.40% and 23.00%, respectively (log-rank, P = 0.0001). The 5-year overall survival rates in the patients having tumors measuring <5 cm and ≥5 cm in size were 82.60% and 71.20%, respectively (log-rank, P = 0.001). Conclusion: A pathological tumor size of ≥5 cm is an independent prognostic factor for local recurrence in rectal adenocarcinoma.