Difference in prognostic impact of lateral pelvic lymph node metastasis between pre- and post-neoadjuvant chemoradiotherapy in rectal cancer patients

PURPOSE: The prognostic significance and treatment of lateral pelvic lymph node metastasis (mLPLN) in rectal cancer patients receiving neoadjuvant chemoradiotherapy (nCRT) are not well understood. In this study, we evaluated the impact of mLPLN identified in imaging modality on outcomes. METHODS: Between January 2008 and December 2016, 1,535 patients who underwent radical resection following nCRT were identified. The association between mLPLN and disease-free survival (DFS), overall survival (OS), local recurrence-free survival (LRFS), and pelvic recurrence-free survival (PRFS) was analyzed, along with risk factors associated with OS and DFS. RESULTS: Overall, 329 (21.4%) of the 1,535 patients experienced disease recurrence; 71 (4.6%) had local recurrence, 25 (1.6%) had pelvic recurrence, and 312 (20.3%) had distant recurrence. The pre- and post-nCRT mLPLN (–) groups had better DFS, LRFS, PRFS, and OS than the (+) groups. LPLN sampling (LPLNs) was implemented in 24.0% of the pre-nCRT mLPLN (+) group and in 28.8% of the post-nCRT mLPLN (+) group. There was no significant difference in OS and LRFS between LPLNs group and no LPLNs group in pre- and post-nCRT mLPLN (+) groups. Pre-nCRT mLPLN was associated with poor OS (hazard ratio [HR], 1.43; P = 0.009) and post-nCRT mLPLN was associated with poor DFS (HR, 1.49; P = 0.002). CONCLUSION: Pre- and post-nCRT mLPLN (+) have different prognostic effects. Post-nCRT mLPLN appears to be more important for disease control. However, pre-nCRT mLPLN should not be disregarded when devising a treatment strategy since it is an independent risk factor for OS.