Post-hoc analysis of clinicopathological factors affecting lateral lymph node metastasis based on STELLAR study for rectal cancer

Abstract

Purpose: In post-hoc analyses of phaseIII randomized controlled study(STELLAR), to analyzethe prognostic impact oflateral pelvic lymph node (LPLN)metastasis in locally advanced rectal cancer (LARC).

Methods: LPLN metastasis was defined as a short diameter > 7 mm on magnetic resonance imaging (MRI).The studyincluded 591 patients with LARC.All patients received neoadjuvant (chemo)radiotherapy combined withradical resection.

Results: Among 591 patients, 99 (16.8 %) were diagnosed with LPLN metastasis, mostly with unilateral metastasis (79.8 %), with internal iliac lymph node metastasis being more common (81.8 %).Significant differences were found among with and without LPLN metastasis in rectal segmentation (P=0.001),N disease (P<0.001), mesenteric LN metastasis or not (P=0.030). The median follow-up timewas 34.0 months, three-year disease-free survival (DFS),overall survival (OS), andmetastasis-free survival (MFS)were significantly lower in LPLN metastaticgroup than those in LPLN non-metastaticgroup (51.4 % vs. 68.2 %, P<0.001; 71.8 % vs. 84.2 %, P=0.006; 60.8 % vs. 80.1 %,P<0.001), respectively; while there were no significant differences in locoregional recurrence(11.4 % vs. 8.5 %, P=0.564). Multivariate analysis found that LPLN metastasis was an independent prognostic factor affecting DFS (P=0.005), OS (P=0.036),MFS (P=0.001).No significantly survival benefit was observed for the short-term radiotherapy based total neoadjuvant therapy compared to long-term concurrent chemoradiotherapy.

Conclusions: LPLN metastasis observed byMRI should be considered in LARC patients, especially in populations with lowrectal cancer, N2 disease, and mesenteric LN metastasis. LPLN metastasis diagnosed by MRI is a significant and independent risk factor and is associated with worse DFS, OS, MFS.

Keywords: Lateral lymph node dissection; Lateral pelvic lymph nodes; Radiotherapy; Rectal tumors; prognosis.