Evaluation of risk factors for lymph node metastasis in T2 lower rectal cancer to perform chemoradiotherapy after local resection

The oncological outcome of chemoradiotherapy (CRT) after local excision (LE) for T2 lower rectal cancer has demonstrated a high local recurrence (LR) rate. The aim of the present study was to determine the risk factors for lymph node metastasis (LNM) in order to reduce LR in T2 lower rectal cancer after LE and CRT. Specimens were collected from 95 consecutive patients with T2 lower rectal adenocarcinoma who underwent R0 resection by total mesenteric excision or tumor-specific mesenteric excision between January 2008 and December 2018 at Osaka International Cancer Institute. All specimens were checked and evaluated to determine the risk factors for LNM. LNM was observed in 26 patients (27%), including 2 patients (2%) with lateral pelvic lymph node metastasis. Univariate analysis indicated lymphovascular invasion (LVI; P=0.008), tumor budding (P=0.012) and histology other than well-differentiated adenocarcinoma (P=0.08) were associated with LNM; multivariate analysis revealed that LVI (P=0.03) was the only independent risk factor for LNM. LNM was confirmed in 0% (0/8) of patients without LVI, tumor budding and histological type. LVI, tumor budding and histological type can be risk factors for LNM in lower rectal cancer. The present study may be helpful to select patients for performing LE and CRT with good oncological outcome.