Prediction of lymph node metastasis in oral tongue squamous cell carcinoma using the neutrophil‐to‐lymphocyte ratio and platelet‐to‐neutrophil ratio

Abstract Background Lymph node metastasis in a variety of tumors is associated with systemic inflammatory markers. However, this association has not been reported in oral tongue squamous cell carcinoma (OTSCC). This study aimed to investigate how the preoperative neutrophil‐to‐lymphocyte ratio (NLR) and platelet‐to‐neutrophil ratio (PNR) in OTSCC patients correlated with the occurrence of OTSCC and lymph node metastasis. Methods The data of 73 patients with primary OTSCC who underwent surgical resection were retrospectively analyzed. Patients with other malignant tumors, patients who had received radiotherapy or chemotherapy before surgery, and patients with active inflammation were excluded. The enrolled patients were divided into groups N0 (no early‐stage lymph node metastasis) and N1 (early‐stage lymph node metastasis). Venous blood samples were collected before surgery and at the third week after surgery and subjected to complete blood counting in a blood analyzer. Eighty‐seven healthy people were included as a control group. In addition, the NLR and PNR in OTSCC patients were compared with those in the controls, and the postoperative NLR and PNR of group N0 were compared with those of group N1. Results The NLR was significantly higher in the OTSCC patients than the controls (p < 0.05). The area under the receiver operating characteristic curve was 0.595. Further comparison of the NLR and PLR between group N0 and group N1 showed that when NLR was ≤1.622, and the probability of early‐stage lymph node metastasis in OTSCC patients was 73.3%, and when PNR was >60.889, the probability was 86.7%. In re‐examination 3 weeks postoperatively, the NLR and PNR were not significantly different between groups. Conclusion The NLR has certain reference value for the diagnosis of OTSCC. The preoperative NLR and PNR can be used to predict early‐stage lymph node metastasis in patients with histopathologically confirmed OTSCC.


| INTRODUC TI ON
Oral tongue squamous cell carcinoma (OTSCC) is one of the most common oral malignancies, and its incidence has been rising in recent years. Because the tongue is rich in blood vessels and lymphatic vessels, it is prone to lymph node metastasis. Therefore, the prognosis of OTSCC is poor, and the 5-year survival rate is low. 1,2 Although lymph node micrometastases sometimes cannot be detected by clinical examinations such as palpation, ultrasound, computed tomography (CT), and magnetic resonance imaging (MRI), they can be revealed by postoperative pathological examination. Such micrometastases are called occult lymph node metastases. 3,4 Up to 33% of OTSCC cases may have occult lymph node metastasis that is currently undetectable by imaging techniques. 5 In patients with OTSCC, the survival rate of patients with cervical lymph node metastasis is 50% lower than that of patients without cervical lymph node metastasis. 6 Therefore, preoperative diagnosis of cervical lymph node metastasis in patients with OTSCC is difficult but important in clinical practice. In addition, patients without lymph node metastasis (N 0 ) tend to suffer unnecessary complications such as intraoperative risk and shoulder joint dysfunction if they receive cervical lymph node dissection, whereas if patients with occult lymph node metastases do not undergo lymph node dissection, they tend to have a high risk of short-term local recurrence and poor prognosis. 7 The early diagnosis of OTSCC and risk assessment of lymph node metastasis still lack readily available and reliable molecular markers. In the past few years, the relationship between tumors and inflammation has become a research hotspot. Tumor cells promote systemic inflammatory responses and cause changes in white blood cell (WBC) and platelet (PLT) counts in peripheral blood. 8 They mainly mediate these changes by releasing stress-related substances and proinflammatory cytokines, such as tumor necrosis factor α, which in turn can affect the occurrence and progression of tumors. 9 Therefore, the neutrophil-to-lymphocyte ratio (NLR), the platelet-to-lymphocyte ratio (PLR), and the platelet-to-neutrophil ratio (PNR) of the peripheral blood obtained from a complete blood count have been used as indicators of systemic inflammation, and the diagnostic and prognostic value of NLR, PLR, and PNR for multiple tumors has been investigated. Current studies have found that NLR, PLR, and PNR have important reference value for the early diagnosis of lung cancer, liver cancer, breast cancer, and colorectal cancer as well as the prediction of lymph node metastasis. [10][11][12][13] However, the relationships of NLR and PNR with the occurrence and development of OTSCC have not been reported.
This study aimed to evaluate the value of NLR and PNR in peripheral blood for the diagnosis of OTSCC and the prediction of cervical lymph node metastasis to provide a reference for the development of surgical plans for OTSCC patients. The OTSCC patients were divided into groups N 0 (no early-stage lymph node metastasis) and N 1 (early-stage lymph node metastasis). Early-stage refers to primary tumor in T 1 stage (tumor ≤2 cm with depth of invasion DOI ≤ 5 mm) or T 2 stage (tumor ≤2 cm, with DOI > 5 mm and ≤10 mm; or tumor >2 cm and ≤4 cm, with DOI ≤ 10 mm). During the same period, 87 healthy individuals were included in the control group (group HC).

| General information
This study was approved by the Ethics Committee of the Ninth People's Hospital affiliated to Shanghai JiaoTong University School of Medicine, and all participants signed informed consent forms.

| Complete blood count
Venous blood samples of each OTSCC patient were collected before surgery and 3 weeks after the surgery. Each sample was immediately mixed with K2-ethylenediaminetetraacetic acid (EDTA) in anticoagulation vacuum tubes. The sample was submitted to a complete blood count within 4 h of sample collection in a blood analyzer. Venous blood samples of patients in group HC were also collected for a complete blood count.

| Statistical analysis
SPSS was used for statistical analysis. The independent-samples t test, the chi-squared test, and receiver operating characteristic (ROC) curve analysis were used for intergroup comparisons. p < 0.05 was considered statistically significant.

| General information of patients
There was no significant difference in the general information between group N 0 and group N 1 . The detailed results are shown in Table 1.

| NLR level in OTSCC patients
The OTSCC patients had lower lymphocyte and PLT counts than the controls (p < 0.05), though their neutrophil counts were similar (p > 0.05). The PLR and PNR of OTSCC patients were not significantly different from those of the controls, while the NLR level of OTSCC patients was higher than that of the controls (p < 0.05) ( Table 2). The ROC curve analysis showed that the area under the ROC curve (AUC) of NLR was 0.595, with the 95% confidence interval (CI) of 0.504-0.686. The Youden index analysis showed that the threshold or cutoff value of the NLR was 2.059 and that the sensitivity and specificity of NLR to diagnose OTSCC were 46.6% and 79.3%, respectively (Figure 1).

| Evaluation of the predictive value of NLR and PNR for early-stage lymph node metastasis in patients with histopathologically confirmed OTSCC
Compared with group HC, group N 0 had a higher NLR (p = 0.0001) and lower PNR (p = 0.0001), and group N 1 had a higher PNR (p = 0.017).
Compared with group N 0 , group N 1 had a lower NLR (p = 0.001) and higher PNR (p = 0.0001) ( Table 2). Changes in NLR and PNR in groups N 0 and N 1 were analyzed using ROC curves. The NLR had the AUC of 0.769, the 95% CI of 0.649-0.889, the cutoff value of 1.6223, and the sensitivity of 73.3% in predicting early-stage lymph node metastasis. The PNR had the AUC of 0.762, the 95% CI of 0.649-0.875, the cutoff value of 60.8892, and the sensitivity of 86.7% in predicting early-stage lymph node metastasis ( Figure 2, Table 3). However, at the third postoperative week, there was no significant difference in the NLR or PNR between groups N 0 and N 1 ( Table 2).

| DISCUSS ION
There is a controversy regarding the treatment of cervical lymph nodes in N 0 patients at the early stage of oral squamous cell carcinoma (OSCC). Some researchers advocate a wait-and-see strategy, which suggests that lymph node dissection should be performed only after confirmation of lymph node metastasis. However, this treatment regimen significantly reduces the survival rate of patients.
Extended resection of the primary tumor(s) combined with cervical lymph node dissection has a high cure rate. Due to the extended scope of surgery, this may lead to early functional impairment or loss and thus affect the quality of life of the patients. 15 Therefore, how to effectively assess noninvasive treatment for cervical lymph nodenegative patients with enlarged cervical lymph nodes or a high risk for metastasis has been the focus of clinical studies.
This study first analyzed the NLR levels in the OTSCC group.
Compared with group HC, the OTSCC group had a significantly higher NLR, mainly due to the lower absolute lymphocyte count and the (nonsignificantly) higher average absolute neutrophil count in the OTSCC group. According to the absence or presence of lymph node metastasis, the OTSCC group was divided into groups N 0 and N 1 . This analysis showed that the absolute neutrophil count in group N 1 was significantly lower than that in group N 0 and that the Note: Data are presented as numbers, and the data were calculated by different etiologies.
absolute lymphocyte count and the absolute PLT count in group N 1 were not significantly different from those in group N 0 . As a result, compared with group N 0 , group N 1 had a significantly lower NLR, a significantly higher PNR, and a nonsignificantly different PLR. The causes for the differences between groups N 0 and N 1 might be that when the OTSCC did not metastasize (group N 0 ), the innate immunity was dominant, so the neutrophil count was elevated. Our results did show that the absolute neutrophil count in group N 0 was significantly higher than that in group HC. 16 After tumor metastasis (group N 1 ), the innate immunity was weakened, adaptive immunity began to play a dominant role, the neutrophil count dropped significantly lower than that before tumor metastasis (group N 0 ), and the mean lymphocyte count was (nonsignificantly) larger than that in group N 0 , resulting in the lower NLR and the higher PNR in group N 1 . 17