The Prognostic Role of the Platelet-Lymphocytes Ratio in Gastric Cancer: A Meta-Analysis

Background
Systemic inflammatory parameters, such as the elevator PLR (platelet-lymphocyte ratio), the NLR (neutrophil-lymphocyte ratio) and the platelet count (PLT), have been found to be associated with the prognosis in gastric cancer; however, these results, especially those relating to the PLR, remain inconsistent. So we aimed to evaluate the prognostic role of the PLR in gastric cancer by conducting and presenting the findings of this meta-analysis.
Methods
We conducted a systematic literature search in PubMed, Embase and the Cochrane Library to evaluate the prognostic value of the PLR in gastric cancer. The quality of the included studies was evaluated using the Newcastle Ottawa Quality Assessment Scale (NOS). The hazard ratio (HR) /Odds Ratio (OR) and its 95% confidence were pooled using a random effects model. A funnel plot based on overall survival was used to evaluate the publication bias.
Results
It total, 8 studies comprising 4513 patients with gastric cancer met the pre-setting inclusion criteria. In comparison to the normal PLR, an elevated PLR was correlated with a higher risk of lymph node metastasis with an OR of 1.50 (95% Cl:1.24–1.82; I2 = 17%) and serosal invasion (T3 +T4) risk with an OR of 2.01 (95% Cl: 1.49–2.73; I2 = 55%), and an elevated PLR also increased the advanced stage (III +IV) risk with an OR of 1.99 (95% Cl: 1.60–2.46; I2 = 28%). An elevated PLR was not a reliable predictor for OS with an HR of 0.99 (95% CI: 0.9–1.1; I2 = 12%).
Conclusions
An elevated PLR was correlated with a higher risk of lymph node metastasis, serosal invasion and advanced stage (III +IV) risk in gastric cancer; however, the PLR may not act as a negative predictor for the overall survival of gastric cancer.

## 研究背景
系统性炎症指标，如升高的血小板淋巴细胞比值（platelet-lymphocyte ratio, PLR）、中性粒细胞淋巴细胞比值（neutrophil-lymphocyte ratio, NLR）以及血小板计数（platelet count, PLT），现已证实与胃癌预后相关；但现有研究结果尚存争议，尤以PLR相关结论为甚。为此，本研究通过开展本项荟萃分析并汇报其结果，旨在探讨PLR在胃癌预后评估中的作用。

## 研究方法
本研究在PubMed、Embase及Cochrane图书馆中开展系统性文献检索，以评估PLR对胃癌的预后价值。采用纽卡斯尔-渥太华量表（Newcastle Ottawa Quality Assessment Scale, NOS）对纳入研究的质量进行评价。采用随机效应模型合并风险比（hazard ratio, HR）、比值比（odds ratio, OR）及其95%置信区间。采用基于总生存期的漏斗图评估发表偏倚。

## 研究结果
共计8项符合预设纳入标准的研究被纳入，涉及4513例胃癌患者。与正常PLR水平相比，升高的PLR与更高的淋巴结转移风险相关（OR=1.50，95%置信区间：1.24~1.82；I²=17%），同时与浆膜侵犯（T3+T4期）风险升高相关（OR=2.01，95%置信区间：1.49~2.73；I²=55%）；此外，升高的PLR还会增加胃癌进展至Ⅲ+Ⅳ期的风险（OR=1.99，95%置信区间：1.60~2.46；I²=28%）。升高的PLR并不能作为胃癌总生存期的可靠预测因子（HR=0.99，95%置信区间：0.9~1.1；I²=12%）。

## 研究结论
胃癌患者中，升高的PLR与淋巴结转移、浆膜侵犯及Ⅲ+Ⅳ期进展风险升高密切相关；但PLR或许并不能作为胃癌总生存期的不良预测因子。