Is lateral pelvic lymph node dissection necessary for good responder to neoadjuvant chemoradiation in locally advanced rectal cancer?

Abstract

Background: Response to preoperative chemoradiation (CRT) is an important indicator of the possibility of lateral pelvic lymph node (LPN) metastasis. However, the effect of LPN dissection (LPND) in good responders to CRT remains unclear. This study aimed to identify the optimal treatment strategy for patients with rectal cancer who respond well to preoperative CRT.

Methods: This multi-institutional retrospective study evaluated patients with locally advanced rectal cancer and clinically suspected LPN metastases who underwent total mesorectal excision with LPND after CRT. The patients were divided into two groups based on the largest lymph node diameter post-CRT (cutoff: 5 mm): good (n = 38) and poor responders (n = 53).

Results: LPN metastasis was significantly higher in poor responders (18 patients, 34.0 %) than in good responders (5 patients, 13.2 %) (p = 0.024). All 5 patients in the good responder group had low rectal cancer (i.e., tumors located within 5 cm from the anal verge (AV)). Low rectal cancer was the only significant predictor for LPN metastasis in good responders (p = 0.004). However, LPN size before and after CRT did not predict LPN metastasis in this group (p = 0.947 and 0.910, respectively). When LPND was indicated for all poor responders and for good responders with tumors located ≤5 cm from the AV, the sensitivity for LPN metastasis diagnosis was 100 %.

Conclusion: Among rectal cancer patients with good response to preoperative CRT, pathological LPN metastasis occurs in 13.2 %, and tumor height is a significant risk factor for LPN metastasis. LPND might be considered for low rectal tumors, regardless of preoperative CRT response.

Keywords: Good response; Lateral pelvic lymph node dissection; Neoadjuvant chemoradiation; Rectal cancer.