Abstract
BACKGROUND: In the context of surgical treatment for rectal cancer, the dentate line is acknowledged as a critical anatomical landmark. However, the prognostic implications of dentate line invasion (DLI) remain elusive and warrant further investigation. This study aims to evaluate and compare the outcomes of patients with rectal cancer who underwent abdominoperineal resection (APR), distinguishing between those with and without DLI. MATERIALS AND METHODS: Between January 2006 and December 2017, this study enrolled 1854 patients with rectal cancer who underwent APR. The cohort was divided into two groups, namely the DLI group (n = 340) and the non-DLI group (n = 1514). The primary endpoints were distant relapse-free survival (DRFS) and local recurrence-free survival (LRFS). Univariate and multivariate analyses were conducted to assess the impact of DLI on DRFS, LRFS, overall survival (OS), and disease-free survival (DFS). RESULTS: The median follow-up duration for the patients was 92.9 months, with a 5-year OS rate of 92.0% for the entire cohort. Compared to the non-DLI group, patients in the DLI group showed significantly poorer outcomes, with 5-year DRFS at 57.4% vs. 73.9% (P < 0.001), DFS at 51.2% vs. 70.7% (P < 0.001), and LRFS at 71.7% vs. 88.5% (P = 0.018). OS was the only metric that showed no significant difference(89.0% vs. 92.6%, P = 0.064). Multivariate analysis demonstrated that DLI negatively impacted DRFS (hazard ratio HR 1.319, P = 0.029), LRFS (HR 2.059, P < 0.001), and DFS (HR 1.563, P < 0.001) as an independent prognostic factor. Furthermore, distant metastasis occurred more frequently in the DLI group (30.0% vs. 23.1%, P = 0.002), along with a higher rate of locoregional recurrence. (16.8% vs. 8.3%, P < 0.001). CONCLUSIONS: DLI correlates with a heightened likelihood of locoregional recurrence and distant metastasis among rectal cancer patients treated with APR. This association underscores the significance of DLI as a crucial prognostic factor that should be considered when developing clinical management strategies.