Long-Term Outcomes and Lymph Node Metastasis in Patients Receiving Radical Surgery for Pathological T1 Lower Rectal Cancer

Abstract

Background: Few reports have evaluated the long-term outcomes of pathological T1 (pT1) lower rectal cancer (LRC), perhaps because pT1 LRC is classified as TNM stage I if lymph node metastasis (LNM) is absent and stage IIIA if LNM is present. Moreover, it is difficult to diagnose regional LNM preoperatively. This study aimed to clarify the long-term outcomes of radical surgery for pT1 LRC and risk factor(s) for LNM. Additionally, we examined whether preoperative computed tomography (CT) and magnetic resonance imaging (MRI) findings were predictive of LNM in pT1 LRC. Methods: This was a retrospective analysis of the clinical characteristics, short-term operative outcomes, and long-term survival rates of 155 patients who received radical surgery and were diagnosed with pT1 LRC at our hospital between January 1993 and February 2017. Results: Among patients with pT1 LRC, 5-year recurrence-free and overall survival rates were 94.0% and 95.8%, respectively. LNM status was not associated with statistically significant differences in recurrence-free or overall survival. Even in patients with LNM, the recurrence rate was only 9%. Among patients who lacked visible mesorectal lymph nodes on preoperative CT and MRI, LNM rates were 3.5% and 4.3%, respectively. Conclusion: The long-term outcomes after radical surgery for pT1 LRC are satisfactory or good, regardless of the presence or absence of LNM. In patients with pT1 LRC, the absence of visible mesorectal lymph nodes on preoperative CT and MRI is associated with a reduced likelihood of LNM and has a high negative predictive value for LNM.