Lymph node metastasis following chemoradiotherapy in advanced rectal cancer: ypT2-focused analyses of total mesorectal excision specimens

Background Non-radical management is an option for good responders to neoadjuvant chemoradiotherapy in mid-to-low rectal cancer. This study aimed to analyze risk factors for lymph node metastasis in patients with ypT2 rectal cancer, exploring the possibility of non-radical management. Methods We included patients with ypT2 rectal cancer who received neoadjuvant chemoradiotherapy followed by total mesorectal excision between January 2004 and December 2022. Clinicopathological parameters were evaluated to identify risk factors for lymph node metastasis. Results Among the 198 patients, 158 (79.8%) had ypT2N0 and 40 (20.2%) had ypT2N+. In univariable analyses, the risk factors of lymph node metastasis were perineural invasion (48.0% vs. 16.3% without perineural invasion, P < 0.001), female sex (30.0% vs. 14.8% with male sex, P = 0.011), and clinically positive nodes after neoadjuvant chemoradiotherapy (32.6% vs. 16.4% with negative nodes, P = 0.017). These factors were confirmed as independent risk factors in multivariable analyses: perineural invasion (odds ratio [OR]: 4.50; 95% confidence interval [CI]: 1.79-11.29; P < 0.001), female sex (OR: 2.62; 95% CI: 1.24-5.52; P = 0.012) and clinical node involvement after neoadjuvant chemoradiotherapy (OR: 2.28; 95% CI: 1.03-5.05; P = 0.012). The rate of lymph node metastasis in patients with ypT2 rectal cancer without any of these three risk factors was 12.5%. Conclusions This study revealed a high probability of lymph node metastasis in patients with ypT2 rectal cancer, even in the absence of identifiable risk factors. We confirm that lymph node metastasis should be considered in ypT2 rectal cancer.