Abstract
Thrombocytosis has been implicated as a potential prognostic biomarker in various malignancies, but its role in endometrial cancer (EC) remains unclear. This retrospective cohort study evaluated the prognostic value of elevated preoperative platelet count (PLT) in patients with EC. A total of 548 patients treated at Changhua Christian Hospital between 2010 and 2021 were included. Patients were classified into high (>400 × 109/L) and normal PLT groups, and propensity score matching was applied in a 1:3 ratio to balance baseline characteristics. Recurrence, disease-free survival (DFS), and overall survival (OS) were assessed using Kaplan–Meier analysis and Cox proportional hazards modeling. After matching, 224 patients were analyzed. The high PLT group demonstrated significantly higher recurrence (37.5% vs 26.8%), shorter DFS (48.2% vs 67.3%), and reduced OS (71.4% vs 83.3%). Adjusted hazard ratios for high PLT were 1.76 for recurrence, 1.98 for DFS, and 2.11 for OS. These findings suggest that thrombocytosis is an independent prognostic factor in EC and may serve as a useful tool for risk stratification and treatment planning.
Keywords
Introduction
Endometrial cancer (EC) is the fifth most common malignancy among women in Taiwan, with most patients diagnosed at an early stage and achieving a favorable 5-year overall survival (OS) rate of approximately 95% for localized disease.1,2 However, the prognosis markedly worsens in cases of recurrence or metastasis, with 5-year survival declining to less than 20%. 3 Despite advances in diagnostic methods and therapeutic strategies, predicting outcomes in EC remains challenging and heterogeneous.
Recent studies have demonstrated that hematological parameters such as preoperative anemia, thrombocytosis, and leukocytosis are associated with poor prognosis in EC, highlighting their potential value as prognostic biomarkers,4–6 underscoring their potential utility as prognostic indicators. Among these, elevated platelet (PLT) counts have been identified as a potential predictor of unfavorable outcomes not only in EC but also in various other malignancies, including ovarian, colorectal, gastric, and lung cancers.7–10 Biologically, platelets facilitate tumor progression by promoting angiogenesis, protecting tumor cells from immune surveillance, and aiding metastasis through multiple molecular pathways. 11 Given these pro-tumorigenic functions of platelets, several clinical studies have explored their prognostic relevance in EC.
Several studies have linked thrombocytosis with advanced stage, poor differentiation, and aggressive tumor behavior in EC.5,12,13 However, these findings are not universally consistent, and the prognostic relevance of thrombocytosis in Asian populations remains unclear. Furthermore, many prior investigations have relied on univariate or conventional multivariate analyses that may not fully adjust for confounding factors such as comorbidities, tumor biology, and treatment modalities.4,14,15
To address these gaps, this study evaluates the prognostic impact of preoperative thrombocytosis in a large, real-world cohort of Taiwanese patients with EC. By applying propensity score matching (PSM), we aimed to mitigate selection bias and better isolate the independent contribution of PLT count to survival outcomes. This study contributes population-specific evidence to support the incorporation of PLT count into risk stratification and individualized treatment planning in East Asian clinical settings.
Significance Statement
Thrombocytosis has been associated with poor prognosis in several malignancies, including gynecologic cancers.
Previous studies have suggested a link between elevated platelet counts and advanced stage, aggressive histology, and worse survival in endometrial cancer.
Most published evidence on thrombocytosis in endometrial cancer is derived from Western populations, and many studies lack rigorous adjustment for confounders.
This study used a large, well-characterized Taiwanese cohort and applied propensity score matching (PSM) to evaluate the prognostic value of preoperative thrombocytosis in endometrial cancer.
High preoperative platelet counts (>400 × 109/L) were independently associated with increased recurrence and lower disease-free and overall survival.
The association remained robust after multivariate adjustment and sensitivity analyses, confirming thrombocytosis as an independent prognostic biomarker.
Routine platelet count, a widely available and low-cost laboratory test, may be incorporated into preoperative risk stratification models for endometrial cancer.
These findings support further evaluation of thrombocytosis in population-specific prognostic tools and may influence decisions regarding adjuvant therapy or follow-up intensity.
Materials and methods
Patient cohort
A retrospective cohort study was conducted at Changhua Christian Hospital (CCH), a tertiary medical center in central Taiwan. Data were obtained from the CCH Clinical Research Database, which integrates cancer registry records, electronic medical records, laboratory data, outpatient visits, and mortality records. A total of 860 patients diagnosed with EC between January 1, 2010 and December 30, 2021, were initially reviewed. Patients with coexisting breast cancer, unspecified pathological diagnoses, or incomplete laboratory data were excluded, yielding a final cohort of 548 patients with EC (Figure 1). The study was approved by the Institutional Review Board of CCH (IRB No. 240710).

Flowchart of participant selection process.
Definition of PLT count and other confounders
Preoperative PLT counts were categorized as high (>400 × 109/L) or normal (≤400 × 109/L), based on established clinical thresholds. 16 Demographic and clinical variables were extracted, including age, body mass index (BMI), menopausal status, smoking and alcohol history, International Federation of Gynecology and Obstetrics (FIGO) stage, lymphovascular invasion, histologic subtype, comorbidities (hypertension and diabetes), and preoperative laboratory parameters. Laboratory tests included hemoglobin (Hb), red blood cell distribution width (RDW), hematocrit (Hct), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), and cancer antigen 125 (CA-125).
Study outcomes
Patients were followed according to institutional guidelines, with clinical evaluations conducted every 3 months during the first 2 years post-treatment and semiannually thereafter. The primary objective of this study was to assess the long-term impact of preoperative PLT count on recurrence and survival outcomes in patients with EC who had undergone surgical intervention.
Recurrence was defined as radiologic or histologic evidence of disease during follow-up. Disease-free survival (DFS) was measured from the date of initial diagnosis to the first documented recurrence, secondary primary EC, or death from any cause. OS was defined as the time from diagnosis to cancer-related death or the end of the study period, whichever occurred first.
Statistical analysis
Continuous variables were reported as medians with interquartile ranges (IQRs), while categorical variables were summarized as counts and percentages. Group comparisons were performed using the Chi-square test for categorical variables and the Mann–Whitney U test for continuous variables. To address baseline differences between groups, PSM was conducted using a 1:3 optimal matching algorithm based on variables selected for their established prognostic relevance to both thrombocytosis and EC outcomes (age, FIGO stage, Hb, RDW, MCV, MCHC, and CA-125). Propensity scores were estimated using logistic regression. Optimal matching was applied to maximize covariate balance while retaining the greatest number of cases. After matching, baseline characteristics were well balanced between groups. This methodological approach—including covariate selection, propensity score estimation, and optimal matching—is supported by prior comparative methodological research and its widespread use in observational studies.17,18
Survival outcomes were analyzed using the Kaplan–Meier method, and differences between groups were assessed with the log-rank test. Multivariable Cox proportional hazards regression models were used to estimate hazard ratios (HRs) for recurrence, DFS, and OS across PLT groups. Subgroup analyses were stratified by demographic variables and FIGO stage (I–II vs III–IV), and continuous variables were dichotomized by their median values.
A sensitivity analysis using an alternative PLT cutoff (>390 × 109/L) was also performed to assess the robustness of findings. All statistical analyses and graphical visualizations were conducted using SAS version 9.4 (SAS Institute Inc., Cary, NC, USA) and R version 4.3.2 (R Foundation for Statistical Computing, Vienna, Austria). A two-sided p-value < 0.05 was considered statistically significant.
Results
Clinical characteristics of the high PLT and normal PLT groups
The demographic and clinical characteristics of the patients are presented in Table 1. Of the 548 patients, 58 exhibited elevated PLT and 490 had normal PLT counts. Prior to PSM, significant differences were observed between the high and normal PLT groups in terms of age (p < 0.001); postmenopausal status (p < 0.001); FIGO stage (p = 0.002); and preoperative Hb (p < 0.001), RDW (p < 0.001), Hct (p < 0.001), MCV (p < 0.001), MCH (p < 0.001), MCHC (p < 0.001), and CA-125 (p < 0.001). Based on these findings, PSM was performed at a 1:3 ratio, resulting in a matched cohort of 224 patients that comprised 56 in the high PLT group and 168 in the normal PLT group with well-balanced clinical characteristics (Table 1).
Demographic and clinical characteristics of participants, stratified by preoperative platelet (PLT) count before and after PSM.
BMI: body mass index; CA-125: cancer antigen 125; FIGO: international federation of gynecology and obstetrics; HCT: hematocrit; MCV: mean corpuscular volume; MCH: mean corpuscular hemoglobin; MCHC: mean corpuscular hemoglobin concentration; PLT: platelet; RDW: red blood cell volume distribution width.
Data are presented as median (interquartile range) or frequency (%).
Long-term outcomes and the influence of preoperative PLT count on prognosis
To assess the influence of preoperative PLT count on prognosis, the 5-year prevalence of recurrence, DFS, and OS were analyzed on the basis of the PLT count. The median follow-up time was 5.1 (IQR: 2.9–7.7) years. The 5-year prevalence rates of recurrence, DFS, and OS for the overall population were 29.9%, 31%, and 14.4%, respectively. After PSM, these rates for the matched patients were 29.5%, 37.5%, and 19.6%, respectively.
Figure 2 presents Kaplan–Meier survival curves comparing 5-year recurrence, DFS, and OS between the two groups after PSM. The Kaplan–Meier survival curves indicate that patients with a high PLT count exhibited significantly higher recurrence rates (37.5% vs 26.8%, p = 0.033), shorter DFS (48.2% vs 67.3%, p = 0.003), and lower OS (71.4% vs 83.3%, p = 0.017) than those with normal PLT counts.

Kaplan–Meier curves after propensity score matching (n = 224) stratified by (a) cumulative recurrence, (b) disease-free survival (DFS), and (c) overall survival (OS), according to preoperative platelet (PLT) count. Shaded areas denote 95% confidence intervals; p-values are from log-rank tests. The median DFS was 2.95 years (≈35 months) in the high-PLT group and was not reached in the normal-PLT group; median OS and recurrence times were not reached during the 5-year follow-up.
To investigate the association between high preoperative PLT counts and EC survival, Cox regression analysis was conducted. The results revealed that patients with a high PLT count exhibited a significantly higher risk of recurrence, DFS, and OS events than those with normal PLT counts. The HR after PSM was 1.76 (95% CI: 1.05–2.96, p = 0.032) for recurrence, 1.98 (95% CI: 1.26–3.11, p = 0.003) for DFS, and 2.11 (95% CI: 1.14–3.90, p = 0.018) for OS (Table 2).
Results of the univariate and multivariate analysis of prognostic factors in the PLT groups before and after PSM.
CI: confidence interval; DFS: disease-free survival; HR: hazard ratio; OS: overall survival; PLT: platelet.
In a multivariate Cox proportional-hazard regression analysis by using Firth’s penalized method, age, postmenopausal status, FIGO stage, hemoglobin level, RDW, MCV, MCHC, and CA-125 were adjusted for.
Supplemental Table S1 presents the results of the sensitivity analysis, which are consistent with the primary study findings.
Subgroup analysis of the influence of preoperative PLT count on prognosis
A subgroup analysis was conducted to investigate the influence of preoperative PLT count on prognosis. The results revealed no interaction effect between PLT count and clinical outcomes (Figure 3).

Subgroup analysis of high preoperative PLT count on (a) recurrence, (b) DFS, and (c) OS.
Additional risk factors for EC prognosis
The results of the risk factor analysis (Figure 4) revealed that the primary factors that contributed to recurrence were age (aHR: 1.02, 95% CI: 1.00–1.04, p = 0.047) and FIGO stage (III–IV vs I–II; aHR: 1.97, 95% CI: 1.33–2.91, p < 0.001). Conversely, a higher preoperative MCV level (aHR: 0.98, 95% CI: 0.95–1.00, p = 0.043) was associated with a lower risk of recurrence (Figure 4(a)). The factors that significantly influenced poorer DFS were age (aHR: 1.03, 95% CI: 1.01–1.05, p = 0.001) and FIGO stage (III–IV vs I–II; aHR: 2.98, 95% CI: 2.10–4.23, p < 0.001; Figure 4(b)). Moreover, the significant risk factors for poorer OS were age (aHR: 1.04, 95% CI: 1.02–1.07, p = 0.001), FIGO stage (III–IV vs I–II; aHR: 4.31, 95% CI: 2.62–7.11, p < 0.001), and CA-125 level (aHR: 1.89, 95% CI: 1.13–3.17, p = 0.016; Figure 4(c)).

Analysis of other prognostic risk factors for (a) recurrence, (b) DFS, and (c) OS.
Discussion
This study demonstrates that high preoperative PLT counts (>400 × 109/L) are independently associated with adverse clinical outcomes in EC, including increased recurrence and reduced disease-free and OS. By employing PSM, we minimized potential confounding and confirmed the prognostic value of thrombocytosis using a methodology that approximates randomized comparisons. Subgroup and sensitivity analyses further corroborated the robustness and consistency of this association. As iron deficiency and anemia are well-recognized causes of secondary (reactive) thrombocytosis, 19 we incorporated hematologic indices reflecting iron status—such as Hb, RDW, MCV, and MCHC—into the PSM model to balance these confounders between groups. This approach strengthens the inference that thrombocytosis represents an independent prognostic marker in EC rather than a byproduct of nonmalignant processes. 20
The prevalence of thrombocytosis in this cohort (10.6%) aligns with previously reported rates.21,22 Although a PLT threshold of >400 × 109/L is commonly used to define thrombocytosis, 15 prior studies have explored alternative cutoffs. Notably, one study reported that a threshold of 350 × 109/L was not associated with progression-free or OS, 23 whereas another using a 390 × 109/L cutoff demonstrated significant associations with DFS. 6 Our sensitivity analysis confirmed that a threshold of >390 × 109/L remains prognostically relevant, while 350 × 109/L lacked predictive accuracy in our population.
The biological plausibility of these findings is supported by literature across gynecologic and other solid malignancies. In ovarian cancer, thrombocytosis has been associated with anemia, elevated CA-125, advanced disease, and suboptimal cytoreduction, 24 while in cervical cancer, it has been linked to inferior survival following chemoradiation. 25 In EC, thrombocytosis is related to poor histologic differentiation, lymphovascular space invasion, deep myometrial invasion, cervical extension, and lymph node metastasis. 26 More broadly, thrombocytosis correlates with larger tumor burden, advanced stage, high-grade histology, and enhanced metastatic potential across multiple cancer types.27,28
Importantly, the adverse prognostic significance of thrombocytosis extends beyond gynecologic malignancies. Multiple meta-analyses and large cohort studies have consistently demonstrated that elevated PLT counts are associated with inferior survival outcomes across a range of solid tumors, including lung, gastric, colorectal, and renal cancers. For instance, Zhang et al. 29 reported that thrombocytosis predicted worse OS and more advanced disease stages in a pooled analysis encompassing several malignancies, while Shu et al. 30 confirmed these findings in a comprehensive umbrella review. Collectively, these data reinforce that thrombocytosis serves as a robust, accessible, and clinically meaningful prognostic biomarker both within and beyond gynecologic oncology.
Beyond clinical associations, experimental evidence demonstrates that platelets actively promote tumor progression. Haemmerle et al. 31 comprehensively delineated the molecular mechanisms by which platelet activation enhances tumor survival, angiogenesis, immune evasion, and metastasis. Inflammatory cytokines such as interleukin-1, interleukin-6, and interleukin-11 stimulate thrombopoiesis, while tumor-derived factors activate platelet aggregation.32,33 Activated platelets release pro-angiogenic and immunosuppressive mediators—such as vascular endothelial growth factor, transforming growth factor-beta, and prostaglandin E2—that promote neovascularization and facilitate immune evasion.34,35 Platelet adhesion molecules, including P-selectin and GPIIb/IIIa, enable tumor cells to adhere to the endothelium and extravasate, thereby supporting metastasis.35,36 Tumor cell–induced platelet aggregation also shields cancer cells from natural killer cell–mediated cytotoxicity, thereby enhancing metastatic potential.
Given its wide availability and low cost, PLT count could serve as a practical component of preoperative risk stratification models in EC. Integration with other clinical and molecular parameters—such as CA-125, FIGO stage, and tumor histology—may further improve prognostic precision. Particularly in settings where molecular testing is not routinely accessible, thrombocytosis may serve as a surrogate marker to guide decisions regarding adjuvant therapy and surveillance intensity.
Our findings also underscore the relevance of other known prognostic factors in EC, including elevated CA-125 levels and FIGO stage.37–40 While FIGO recently revised its staging system to incorporate molecular and histologic classifications, 41 our study provides complementary evidence that readily available hematologic parameters retain prognostic value and should not be overlooked.
It is plausible that thrombocytosis reflects an underlying biological phenotype not yet captured by current staging systems. Future studies should investigate the relationship between thrombocytosis and molecular subtypes of EC, such as p53-abnormal or copy-number high tumors, which are associated with poor prognosis. In addition, several methodological and population-specific limitations should be considered when interpreting our findings. Although obesity is a well-established risk factor for EC, 42 our study population was characterized by lower overall BMI values compared with typical Western cohorts, consistent with epidemiologic data indicating a substantially lower prevalence of obesity among East Asian populations. 43 This ethnic and geographic difference may limit the generalizability of our findings. Furthermore, we were unable to fully account for the effects of obesity on PLT count because BMI data were incomplete for some patients and, therefore, were not included in the matching process.
Recent studies suggest that obesity-driven chronic low-grade inflammation may increase PLT counts through upregulation of interleukin-6 and thrombopoietin signaling, 44 potentially influencing both PLT count and EC outcomes. Therefore, the potential impact of metabolic and inflammatory status should be considered when interpreting our results. This limitation highlights the need for future studies in larger, ethnically diverse cohorts with comprehensive metabolic profiling. Finally, the retrospective, single-center design may further limit generalizability, and residual confounding cannot be fully excluded, even with PSM. While our findings support the prognostic role of thrombocytosis in EC, causality cannot be established.
In conclusion, preoperative thrombocytosis is an independent predictor of poor prognosis in Taiwanese patients with EC. These results support the integration of PLT count into clinical decision-making and highlight the need for prospective studies to validate these findings and explore underlying molecular mechanisms.
Supplemental Material
sj-docx-1-imj-10.1177_10815589261422249 – Supplemental material for Influence of thrombocytosis on the prognosis of endometrial cancer: Results from propensity score matching
Supplemental material, sj-docx-1-imj-10.1177_10815589261422249 for Influence of thrombocytosis on the prognosis of endometrial cancer: Results from propensity score matching by Tung-Ying Wu, Pei-Ru Lin, Chew-Teng Kor, Ying-Lin Hsu and Ming-Ju Chen in Journal of Investigative Medicine
Footnotes
Ethical considerations
The study protocol was approved by the Institutional Review Board of Changhua Christian Hospital (IRB No. 240710) and was conducted in accordance with the principles of the Declaration of Helsinki. The requirement for informed consent was waived due to the retrospective nature of the study and the use of de-identified data.
Author contributions
M-JC, P-RL, and T-YW conceived and designed the study. M-JC and T-YW contributed to data acquisition. M-JC and P-RL contributed to statistical analysis. M-JC, C-TK, and Y-LH contributed to data interpretations. M-JC and T-YW contributed to the drafting of the manuscript. C-TK and Y-LH contributed to the final revision of the manuscript. All authors provided critical feedback on the manuscript. All authors have read and agreed to the published version of the manuscript.
Funding
The authors received no financial support for the research, authorship, and/or publication of this article.
Declaration of conflicting interests
The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
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