Lateral pelvic lymph node metastasis in T2 low rectal cancer: is TME alone sufficient for cure?

BACKGROUND: Some patients with even T2 low rectal cancer are known to develop lateral pelvic lymph node metastasis. This study aimed to investigate real-world evidence regarding lateral nodal metastasis on T2 low rectal cancer treatment. METHODS: Consecutive patients with pathological T2 low rectal adenocarcinoma who underwent curative-intent surgery between January 2007 and December 2015 at two Japanese cancer centres dedicated to lateral pelvic lymph node dissection were identified and included in the analysis. Lateral pelvic lymph node metastasis was defined as pathologically confirmed metastatic lateral pelvic lymph node or lateral-local recurrence after primary surgery. RESULTS: A total of 215 consecutive patients, including 101 and 114 patients who did and did not undergo bilateral lateral pelvic lymph node dissection, were included in the analysis. Overall, 19 (8.8%) patients had lateral pelvic lymph node metastasis, including 13 with pathologically confirmed metastatic lateral pelvic lymph node and six with lateral-local recurrence. A total of 10 (4.7%) patients had local recurrence, including six with lateral-local recurrence, two with central-local recurrence and two with anastomotic recurrence. Five/7-year cumulative risks of lateral-local recurrence in patients with and without lateral pelvic lymph node dissection were 1.1/1.1% and 3.9/5.2%, respectively. CONCLUSION: The problem of the relatively high rate of lateral local recurrence remains in treating T2 low rectal cancer with only total mesorectal excision. The selection of high-risk patients of lateral pelvic lymph node metastasis and the indication of additional treatment in T2 low rectal cancer should be discussed further.