This study's objectives are to guide risk-dependent adjuvant therapy for Locally Advanced Esophageal Squamous Cell Carcinoma (LA-ESCC) after esophagectomy, measure survival benefit, and produce a predictive nomogram. An internal validation and independent external validation in a randomized controlled trial were performed as part of this single-center retrospective research of consecutive LA-ESCCs treated by curative-intent esophagectomy. Using the Cox proportional hazards model, a nomogram was created to estimate 5-year Overall Survival (OS) after factor selection by the least absolute shrinkage and selection operator regression. Its discriminative and predictive abilities were assessed using the calibration plot and Area Under the Curve (AUC), respectively. The quantification and plotting of the adjuvant therapy induced improvement in survival were done according to nomogram score. For model creation, internal validation, and external validation, respectively, a total of 1077, 718, and 118 patients were included. Gender, pathological T and N stages, differentiation, surgical margin, lymphovascular invasion, number of lymph nodes removed, and adjuvant therapy were the eight significant prognostic markers found by the nomogram. The nomogram demonstrated improved discriminative ability compared to TNM stage, with substantial differences in survival rates among various risk strata. The calibration plot showed a good level of agreement between the 5-year OS predicted by the nomogram and the actual OS. After external validation, consistent results were drawn. In nearly all patients (nomogram score 110 to 260) and patients mostly at highintermediate risk (nomogram score 159 to 207), an adjuvant chemoradiotherapy or chemotherapy benefit of at least 10% on 5-year OS was anticipated. A highly accurate clinicopathological nomogram for predicting 5-year OS for LA-ESCC following esophagectomy has been devised. The suggested nomogram performed better than TNM stage and offered risk-based, personalized recommendations for adjuvant therapy.
