Key point:
- 7 papers were included in this study, including 1711 patients;
- The results of the analysis were: the merge OS, HR=1.70, 95%CI
1.11-2.61; PFS, HR=1.34, 95%CI 0.47-3.81;
- Subgroup analysis included sample size, cut-off, treatment, variable
and disease stage showed that a poor OS in patients with increased
PLR;
- In patients with laryngeal cancer, an elevated PLR means a poorer
prognosis;
- PLR was available preoperatively and could help physicians determine
the prognosis of prognosis.
Introduction
Laryngeal carcinoma was a common tumor in otolaryngology department. In
China, there were 26,300 new diagnosed patients and 14,500 new deaths
caused by laryngeal cancer in 2015[1]。In United States, laryngeal
squamous cell carcinoma (LSCC) accounted for 13,150 new patients and
3,710 new deaths in 2017 [2]。Literature had shown that for patients
with local disease, the 5-year survival rate was about 75%, patients
with regional invasion was 44%, patients with metastasis was about
35%[3]。Despite improvements in diagnostic techniques and surgical
procedures, the American Cancer Society(ACS) noticed that for patients
with laryngeal cancer the 5-year survival rate had been declining
recently [4]。
Currently, it was considered important to accurately assess the
prognosis of patients before surgery because it could help to select the
appropriate treatment modality and thus promote the quality of life for
patients. TNM staging was considered to be the finest predictor of
long-term survival[5],however it could only be obtained after
surgery, preoperatively available and easily detectable markers were
needed for prognosis assessment, which was conducive to better
personalized treatment.
It was now known that inflammation was a characteristic of tumors and
exert a critical influence in the initiation and development of tumors
[6, 7]. Inflammatory cells such as neutrophils could kill cancer
cells directly through ADCC, T cells were the core of anti-tumor
immunity, which could recognize and kill tumor cells.
In addition, Platelets were now known to release inflammatory mediators
and mitotic materials into the TME (tumor microenvironment), and absorb
more of them, leaded to platelet aggregation [9]. Through TGF-β/Smad
pathway and NF-κB pathway, platelets could interact with tumor cells,
and induce EMT of tumor cells, thereby promoted tumor metastasis[8].
It had been reported that beside peripheral blood
NLR(Neutrophil-Lymphocyte Ration), PLR could also be used to predict the
prognosis of a variety of solid tumors [10, 11],however, the
prognostic role of PLR in laryngeal cancer remains controversial [12,
13].
Meta-analysis was now widely recognized as a powerful statistical tool
for overcoming the limitations of individual studies on different sample
sizes and for deriving best evaluations. Thus, the aim of this article
was to quantitatively analyze the value of preoperative PLR in the
prognosis of laryngeal cancer.
2. Material and methods
2.1 Retrieval methods
A comprehensive literature search was conducted through the following
databases: PubMed, Web of Science, Ovid and The Cochrane Library. Search
criteria updated to 1 May 2021. The searching words were: “PLR” (e.g.,
“platelet-to-lymphocyte ratio”, “platelet lymphocyte ration”,
“PLR”) and “Laryngeal Neoplasm” (e.g., “Laryngeal Neoplasm”,
“Larynx Neoplasms”, “Larynx Neoplasm”, “Cancer of Larynx”,
“Larynx Cancers”, “Laryngeal Cancer”, “Laryngeal Cancers”,
“Larynx Cancer” and “Cancer of the Larynx”). The references of the
retrieved articles were also examined.
2.2 The criteria of inclusion and exclusion
The criteria for inclusion was below:(1)patients with laryngeal cancer
were confirmed by pathology; (2) pathologically confirmed laryngeal
cancer without evidence of metastasis or recurrence; (3) determination
of PLR Value by Serum Test; (4) the relevance of PLR with OS and PFS was
reported; (5) A multivariable / univariate proportional risk model
adjusted for major clinical factors was used for statistical analysis;
(6) NOS score (Newcastle Ottawa Scale) was more than six points are
considered eligible;
The criteria for exclusion were below: (1) The types of articles were
abstracts, reviews, correspondence, case reports and non-clinical
studies; (2) non-English articles; (3) The necessary data to calculate
HR and 95% CI were not provided; (4) Data was duplicated in these
articles.
2.3 Extract data and assess quality
Data from the retrieved articles were extracted and evaluated for
quality by the two separate authors. In the event of disagreement, the
third author participated and a consensus was reached. Each article
needed to record the following content: first author, country, published
time, number of patients, follow-up time, thresholds, treatment options,
tumor types and HRs with 95% CI. NOS score was composed of three parts:
article selection, quality comparison, and result evaluation. A score of
6 or more was considered as high-quality research. Two authors
separately evaluated the quality of included articles using NOS score.
2.4 Statistical method
In accordance with Parmer et al., HR and 95%CI or their approximations
were obtained from the included articles. [12, 13]. P<
0.10 or I2 >50%, indicated notable
heterogeneity. When significant heterogeneity was observed, the
random-effect model was used. Or else, the fix-random effect model was
adopted. The reasons of heterogeneity were discussed by subgroup
analysis, sensitivity analysis and meta-regression.
Results
3.1 The retrieval results
A total of 88 articles were found in the preliminary search. After
thoroughly investigation of these papers, our meta-analysis eventually
included 7 studies involving 1711 patients published between 2016 and
2021. Figure1 summarized the process of research selection. All studies
were from China. HRs and 95%CI were directly provided in these
articles. HRs in 6 articles was calculated by the multivariable and
univariable analysis and HRs in 1 article via univariable analysis. 4
articles enrolled > 200 cases, another 3 included
< 200 cases. The cut-off values provided in these articles
were inconsistent, between 106 to 189. The cut-off value in 4 articles
≤114, the value in another 3 articles > 114. 6 articles
involved all disease stages, 1 article had advanced stage, all of them
reported the interaction between PLR and OS.
Figure 1: Flow Chart for Selection of Qualified Documents.