Background Gastric cancer (GC) is one of the common and fatal cancers. Even though the Tumor, Node, Metastasis (TNM) staging system is the most classical staging system recognized worldwide, it has been controversial because there are various factors affecting the prognosis of GC patients. Objectives The study aims to evaluate the relationship between interleukin-6 (IL-6) and several clinical indicators and construct a prognostic model to better predict the prognosis of GC. Design A retrospective study. Methods Data of 249 patients with GC diagnosed in GC center of West China Hospital were collected. Clinicopathological characteristics were analyzed to determine whether there were differences between IL-6 HIGH group and IL-6 LOW group. Besides, the association between the two groups and tumor marker levels was clarified. The K-M curves of 3- and 5-year were plotted with log-rank test. Afterward, we conducted univariate and multivariate analysis and a predicting nomogram. Significantly, C-index, and calibration were used to evaluate the value of nomogram in predicting prognosis. Results The overall survival of GC in the IL-6 HIGH and IL-6 LOW groups were 47.8 months (95% CI: 42.1-53.4) and 57.9 months (95% CI: 54.1-61.7), respectively, with significant differences (p = 0.0046). Average tumor size of GC (p = 0.000) and nerve invasion (p = 0.018) were statistically significant between two groups. Multivariate analysis revealed that the factors affecting prognosis were IL-6 (<5.51 and ⩾5.51 pg/ml) (Hazard Ratio(HR): 1.665, 95% CI: 1.026-2.703, p = 0.039), N stage (HR: 1.336, 95% CI: 1.106-1.615, p = 0.003), and T stage (HR: 1.268, 95% CI: 0.998-1.611, p = 0.052), which were included in the nomogram with a C-index of 0.71. The current data calculated TNM staging C-index was 0.68, and the p-value for the difference between the two models was 0.08. Internal validation revealed that the predicted overall survival did not differ significantly from the actual observed patient survival. Conclusion The differential expression of IL-6 has a tendency to differentiate the prognosis of GC patients. IL-6, N stage, and T stage are independent prognostic factors, and the new survival prognostic model consisting of the above three indicators is better than the classical TNM staging system. Trial registration This study is a retrospective study, which does not require clinical registration.

中文翻译：

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IL-6 与胃癌预后的关联：一项回顾性研究。

背景胃癌（GC）是常见且致命的癌症之一。尽管TNM分期系统是全球公认的最经典的分期系统，但由于影响GC患者预后的因素较多，因此一直存在争议。目的本研究旨在评估白细胞介素6（IL-6）与多项临床指标的关系，构建预后模型，以更好地预测GC的预后。设计一项回顾性研究。方法收集华西医院胃癌中心确诊的249例胃癌患者资料。分析IL-6 HIGH组和IL-6 LOW组的临床病理特征是否存在差异。此外，还阐明了两组与肿瘤标志物水平之间的关联。采用对数秩检验绘制3年和5年的KM曲线。随后，我们进行了单变量和多变量分析以及预测列线图。值得注意的是，C 指数和校准用于评估列线图预测预后的价值。结果 IL-6 HIGH 组和 IL-6 LOW 组的 GC 总生存期分别为 47.8 个月（95% CI：42.1-53.4）和 57.9 个月（95% CI：54.1-61.7），差异显着（p = 0.0046）。两组间 GC 的平均肿瘤大小 (p = 0.000) 和神经侵犯 (p = 0.018) 具有统计学意义。多因素分析显示，影响预后的因素为IL-6（<5.51且⩾5.51 pg/ml）（风险比（HR）：1.665，95% CI：1.026-2.703，p = 0.039）、N分期（HR：1.336） 、95% CI：1.106-1.615，p = 0.003）和 T 分期（HR：1.268，95% CI：0.998-1.611，p = 0.052），这些都包含在 C 指数为 0.71 的列线图中。当前数据计算出的 TNM 分期 C 指数为 0.68，两个模型之间差异的 p 值为 0.08。内部验证显示，预测的总体生存率与实际观察到的患者生存率没有显着差异。结论 IL-6的差异表达具有区分GC患者预后的倾向。IL-6、N分期、T分期是独立的预后因素，由上述三个指标组成的新的生存预后模型优于经典的TNM分期系统。试验注册本研究为回顾性研究，不需要临床注册。