Association of pretreatment thrombocytosis with prognosis in ovarian cancer: a systematic review and meta-analysis

Objective: To investigate the association between pre-treatment thrombocytosis and prognosis in patients with ovarian cancer (OC). Methods: PubMed, EMBASE, and the Cochrane Library were searched for articles regarding the prognosis of OC patients with pre-treatment thrombocytosis by the end of March 2018. Pooled estimates for overall survival (OS) and progression-free survival (PFS) events were calculated as hazard ratios (HRs) either on a fixed or random effect model by Stata 13.0 software. Funnel plot and Egger's test were applied to evaluate publication bias and sensitivity analyses were undertaken to estimate the strength of outcomes. Results: Eleven studies that met the inclusion criteria were enrolled, including a total of 4,953 patients. Pooled results showed that pre-treatment thrombocytosis was significantly associated with OS (HR=1.722; 95% confidence interval [CI]=1.437-2.064) and PFS (HR=1.452; 95% CI=1.323-1.593) in the cohort. Significant correlation was found in OS and PFS between pre-treatment thrombocytosis and both epithelial OC (all stages and differentiation degrees of OC) and advanced epithelial OC (III or IV) by subgroup analyses, which were performed according to publication year, country, case numbers, OC category, International Federation of Gynecology and Obstetrics stage, and cut-off value. However, subgroup analyses indicated no significant correlation between pre-treatment thrombocytosis and OS for patients with high-grade serous (poorly differentiated or undifferentiated) OC (HR=1.220; 95% CI=0.946-1.573; p=0.125). Egger's test demonstrated no obvious publication bias in the articles enrolled in this study (OS: p=0.226; PFS: p=0.071). Conclusion: Pre-treatment thrombocytosis might be taken as an independent prognostic indicator for patients with OC.