Pretreatment Platelet-to-Lymphocyte Ratio (PLR) is associated with prognosis in gastric cancer patients with immunotherapy

Background: previous studies had demonstrated that system inammation indexes were associated with prognosis ability in various cancers. We aim to explore the prognostic value of platelet to lymphocyte ratio (PLR) in patients with advanced or metastatic gastric cancer (AGC or MGC) receiving immunotherapy. Method: patients with AGC and MGC who received anti-PD-1 treatment at the Chinese PLA General Hospital between January 2016 and August 2020 were reviewed. The study analyzed the association of PLR and overall survival (OS) or progression-free survival (PFS) and anti-tumor response rate with immunotherapy. Results: 137 patients were included in the nal analysis. The area under the curve values of PLR for 6 months PFS was 0.68(P<0.05). The best cut-off value for PLR was 816.43. Patients in PLR <816.43 group had PFS of 7.9m compared to 4.3m in PLR>= 816.43 group (HR = 0.61 , 95% CI, 0.42-0.93, p < 0.001). The objective response rate (ORR) and disease control rate (DCR) were 34.1% and 84.6% respectively in PLR <816.43 group while 30.4% and 80.4% in the>= 816.43 group. No signicant difference was observed among two group in terms of ORR and DCR (p=0.669, p=0.536). Univariate analysis and multivariate analysis found that PLR was an independent prognosis biomarker for PFS and OS(p<0.05). Conclusions: Pre-treatment PLR was signicantly associated with PFS and OS in patients with AGC and MGC who received immunotherapy. Clinicians might consider patients with elevated PLR as one factor for decisions on immunotherapy strategy. into the of immunotherapy. the PFS and OS of chemotherapy in combination with immunotherapy for advanced gastric conrmed in the ATTRICATION4 and Checkmate649 , partial patients from from pd-1 involved Several common and to in to explore value patients with or with other


Background
Gastric cancer is the fth most common cancer worldwide and has the fourth highest mortality rate, accounting for 7.7% of cancer-related deaths [1] . With the recognition of cancer, the Interventions for advanced or metastatic gastric cancer (AGC or MGC) had entered into the era of immunotherapy. Although the prolonged PFS and OS of chemotherapy in combination with immunotherapy for advanced gastric cancer has been con rmed in the ATTRICATION4 and Checkmate649 studies [2,3] , partial patients remain not bene t from treatment from pd-1 involved regime . Several common system in ammation index, such as the neutrophil to lymphocyte ratio (NLR) and platelet to lymphocyte ratio (PLR), have been reported to have prognostic value in various cancers [4][5][6][7][8] , and the elevated NLR or PLR were considered as poor prognostic maker in gastric cancer whenever patients suffered chemotherapy or neoadjuvant therapy [6,[9][10][11] . The study had showed that NLR during nivolumab monotherapy as third line are associated with advanced gastric cancer survival [12] . However, as a convenient index, to our knowledge, few studies have investigated the prognostic value of PLR for patients with AGC or MGC receiving the anti-programmed death protein 1(pd-1) therapy. Our study was rst time to explore the prognostic value of PLR in patients with anti-pd-1 monotherapy or combined with other agents

Patients And Methods
Patients with AGC or MGC administered with immunotherapy between October 1st, 2016 and August 31st, 2020 at Chinese PLA General Hospital were enrolled in the present study retrospectively. Eligible patients must meet the criteria as follows: (1) pathology diagnosed with gastric cancer (2) receiving at least two cycles of anti-PD-1 treatment (3) presence of measurable lesions (4) complete clinical features such as age, gender, Eastern Cooperative Oncology Group Performance Status (ECOG PS), serum tumor makers and response evaluation (5) complete blood count prior to any treatment. Patients received programmed death protein ligand 1 (PD-L1) antibodies or Cytotoxic Lymphocyte Antigen 4(CTLA4) inhibitor was excluded. Finally, 137 patients were included in the present study. This retrospective observational study was approved by the Ethics Committee of Chinese PLA general hospital. All the patients signed the consent.

Treatment and assessment of tumor response
With regard to treatment type, three types of combination compromise of options for patients with AGC and MGC; anti-pd-1 monotherapy or combined with chemotherapy or anti-angiogenic therapy. PD-1-targeting antibodies include Nivolumab,Pembrolizumab, Sintilimabor, Toripalimab(both domestic PD-1 inhibitor in China). Chemotherapy regimens included XELOX (capecitabine 1000 mg/m² twice daily on days 1 to 14 of each cycle plus intravenous oxaliplatin 130 mg/m² on day 1 of each cycle), SOX (S-1 40-60 mg twice daily on days 1-14 plus oxaliplatin 130mg/m2 on day 1) or DCF (docetaxel 75 mg/m2 cisplatin 75 mg/m2 on day 1 plus fluorouracil 750 mg/m2/d), and other alternatives. Angiogenesis inhibitors are striated into small-molecule tyrosine kinase inhibitors (TKI) such as Apatinib and monoclonal antibody such as Bevacizumab. The regimen was based on the patients' condition and preference. All patients signed informed consent for treatment.
The evaluation of tumor shrinkage was in accordance with response Evaluation Criteria in Solid Tumors 1.1. The response degree was categorized as follows: complete response (CR) and a partial response (PR), stable disease (SD), progression disease (PD). Disease control rate was de ned as CR; PR or SD.
Objective responses include CR and PR. Overall survival (OS) was calculated from the initiation of each line treatment to death or the date of the last followup. Progression-free survival (PFS) was de ned as from the date of any active treatment initiation until the date of either the rst progression or death.

Blood sample analysis
Peripheral blood platelet, lymphocyte count before the initiations of pd-1 treatment within one week were obtained from medical laboratory records. The PLR was determined as the platelet count divided by the lymphocyte count. The receiver operating characteristic analyses for predicting 6 months and 12 months PFS was used to identify an appropriate and optimal cutoff level by the PLR. And then, patients were divided into two group based on the cutoff value of PLR.

Statistical analysis
Data analysis was performed using SPSS for Windows, version 22 (SPSS Inc., Chicago, IL, USA). Continuous variables were present as medians and range. Comparisons of the categorical data were using Pearson's chi-square or Fisher's exact test. The relationships between tumor response and the PLR were assessed using the χ2 test. Survival data were analyzed using the Kaplan-Meier method. Comparison of survival curves was performed using log-rank analysis. Cox multivariate was used to verify the independent prognostic parameters. The optimal cut-off value was determined by the Youden Index in ROC

Discussion
Notwithstanding the model of immunotherapy for AGC or MGC patients had become a trend recently; few studies have investigated the value of routine blood parameters in predicting the prognosis in immunotherapy setting. Although PD-L1 expression and tumor mutation burden(TMB) and microsatellites unstable, tumor in ltrating lymphocyte(TIL),which were associated with prognosis in patients with cancer when given immunotherapy have been identi ed [13][14][15][16][17] , these biomarkers largely depend on expensive equipment, di cult technology, time-consuming, and some of them obtained after resection of the primary tumor.
Therefore, reliable and convenient prognostic factors were of importance when making decisions for patients in system therapy.
Systemic in ammation indexes such as NLR, PLR, and MLR were proved as predictors of survival condition in many cancers at great lengths [9,[18][19][20][21][22] .PLR had been demonstrated that play an important role on prognosis of gastric cancer whenever at local advanced or metastatic stage [11,23] . As far as we concerned whether the PLR can also predict the immunotherapy outcomes for AGC or MGC remains unclear. Our study was at rst time providing the evidence that elevated PLR was linked to poor survival and caution must paid on the choices of immunotherapy for patients with GC when PLR level prior to treatment was elevated. Kaplan-Meier survival analysis showed that the curves for PFS and OS in patients with pre-treatment PLR < 816.43and PLR ≥ 816.43 had signi cant differences. Multivariate analysis further demonstrated the predictive value of PLR both in PFS and OS. The nding was consistent with other studies with patients treated with chemotherapy [24] . The underling mechanisms were lack of substantial evidence. Some potential reasons might explain why high PLR is associated with poor survival time. Experimental evidence has showed platelets acts active in all steps of tumor genesis including tumor growth, tumor cell extravasation, and metastasis [25] . Additionally, thrombocytosis in cancer patients is associated with adverse patient survival [26] . The presence of T cells is now a well-supported marker of better prognosis in many tumor types, which attribute to immune regulatory cell populations that promote tumor escape from immune surveillance and metastasis [27] . Lymphocytic in ltration of tumors (TIL) is also linked to the success of immune checkpoint therapeutic strategies [28] . Combined with these ndings, increased platelet-to-lymphocyte was related to negative anti-tumor environment, especially to poor response condition for immunotherapy. Therefore, patients with elevated PLR had inferior survival due to high proportion of tumor-promoting platelet and reduction of tumor -killer lymphocyte.
However, our study analyzed that PLR did not have signi cant prognostic value for predicting the response rate of anti-pd-1 treatment in AGC or MGC. Instead, in some studies, the PLR was correlated with chemotherapeutic response [6,23] . The speci c reasons for different results remain to be elucidated. It is assumed that toxicity of chemotherapy direct effects on local tumor cells while the function of immunotherapy induced the long-term effect instead of short-term outcomes.
In our study, the cut-off value of PLR was calculated as 816.43 with an ROC curve according to the 6 months PFS. The cut-off level was much higher compared with previous studies. The study form Jin Wang analyzed the relationship between PLR and response and survival in rst-line chemotherapy at a cut-off of 201.6 [23] . The highest PLR level from the meta-analysis [24] was at level of 350 based on 28 studies. Differences cut-off between studies might due to different laboratory reference standards.
The study had some limitations. First, this was a retrospective study with limited population. Second, other in ammatory markers such as NLR, MLR were not calculated. Third, the outcome needs validation series.

Conclusion
Pre-treatment PLR has association with prognosis in patients with immunotherapy of metastatic and advanced gastric cancer in this retrospective study. Attention might be paid when immunotherapy was opting to patients with elevated PLR.