ISSN: 2578-482X
Authors: Taha AM*, Saada AM, Amin AT and Jabir MA
Background: Accurate rectal cancer N staging requires the histopathological evaluation of at least 12 lymph nodes. Retrieval of that count is not always possible. The purpose of the study is to evaluate the lymph node ratio (LNR) prognostic significance on overall survival. Methods: The current study is a retrospective cohort study of 229 patients who underwent curative surgery for resectable rectal cancer. Receiver Operating Characteristic (ROC) curve analysis was used to determine the optimal cut-off value for Lymph Node Count (LNC), Positive Lymph Nodes count (PLN), and LNR for overall survival (OS). The Kaplan-Meier product limit method was used for univariate analysis of factors affecting OS. Log Rank (Mantel-Cox) test was used to test significance. A Cox-Regression Hazard model was used to detect the most significant factor affecting OS. Results: ROC curve analysis of the PLNs revealed a poor prognostic value of the test, with a sensitivity of 51.9% at PLNs 4 cutoff value, with a shorter mean OS above it (21.71±11.597 vs. 31.20 ± 16.634 for ≥4 vs. <4). ROC curve analysis of LNC revealed the poor value of the test, with a sensitivity of 56% at LNC 12 cutoff value, with longer mean Overall Survival (OS) above it (28.21±15.432 vs. 22.22±12.97 for LNC ≥12 vs. <12). ROC curve analysis of the LNR revealed good value of the test for predicting survival, with a sensitivity of 95% at LNR 18.82% cutoff value, with longer mean OS above it (21.44±11.607 vs. 39.82±15.085 for LNR ≥18.8% vs. <18.8%). According to our univariate analysis, the factors significantly affecting OS were histopathological examination (p =.000), Lympho-Vascular Invasion (LVI) (p =.014), and the LNC cutoff value (p=.002), the PLN cutoff value (p =.008), and the LNR cutoff value (p =.000. According to our multivariate analysis, the LNR cutoff value of 18.8% was the most significant factor affecting OS (p =.000). Conclusions: A high LNR with an 18.82% cutoff value is an independent adverse prognostic factor affecting OS after curative surgery for cancer rectum. The LNR could be considered a good alternative to the absolute number of PLNs, particularly in patients with a low LNC. A higher LNC ≥12 was associated with a longer OS; maximum possible lymphadenectomy should be performed for each patient.
Keywords: Colorectal Cancer; Lymph Node Ratio; ROC Curve; Overall Survival; Prognosis
