Thrombocytosis Portends Adverse Prognosis in Colorectal Cancer: A Meta-Analysis of 5,619 Patients in 16 Individual Studies

Aim: The current study aimed to determine the prognostic significance of thrombocytosis in patients with colorectal cancer (CRC) by a meta-analysis of the literature.

Patients and methods: The meta-analysis followed the 2009 guidelines of Preferred Reporting Items for Systematic Reviews and Meta-Analyses. A systematic literature review was conducted from PubMed and Web of Science for articles published up to May 15, 2015. Sixteen studies with a total of 5,619 patients met the inclusion criteria. Hazard ratios and 95% confidence intervals were retrieved from the original articles, calculated from the published Kaplan-Meier survival curves, or the corresponding authors were contacted for additional information. Heterogeneity was assessed using the I² statistic and Chi-square tests. Publication bias was assessed by Begg's funnel plot, Egger's linear regression test and trim-and-fill method. Sensitivity analysis was performed to validate the reliability.

Results: Thrombocytosis is associated with shorter overall, disease-free and cancer-specific survival. Overall survival is reduced in patients with thrombocytosis regardless of their clinical tumor stage, and ethnicity. Shortened disease-free survival is associated with elevated platelet count in the non-specific stage (I-IV), localized tumor (stage I-III), and in the Asian patient population. Thrombocytosis is further associated with reduced cancer-specific survival in the non-specific stage and in Asian patients. Finally, thrombocytosis is significantly related to female patients, colon tumor location, T3-4 stage, lymph node positivity, metastasis, undifferentiated histology and lymphatic involvement.

Conclusion: Thrombocytosis portends adverse prognosis in CRC, and may serve as a clinically useful marker to facilitate risk stratification and guide postoperative management.