The association between thrombocytosis and subtype of lung cancer: a systematic review and meta-analysis

ABSTRACT Background Thrombocytosis is associated with poor lung cancer prognosis and has recently been identified as having a high predictive value in lung cancer detection. Lung cancer has multiple histological and genetic subtypes and it is not known whether platelet levels differ across subtypes. Methods PubMed and Embase were systematically searched for studies that reported pre-treatment platelet count, as either averages or proportion of patients with thrombocytosis, by histological subtype of lung cancer. Suitable studies were synthesised in meta-analyses; subgroup analyses examined for differences across subtypes. Results The prevalence of pre-treatment thrombocytosis across all lung cancer patients was 27% (95% CI: 17 to 37%). By subtype, this was 22% (95% CI: 7 to 41%) for adenocarcinoma (ADC), 28% (95% CI: 15 to 43%) for squamous cell carcinoma (SCC), 36% (95% CI: 13 to 62%) for large cell carcinoma, and 30% (95% CI: 8 to 58%) for small cell lung cancer (SCLC). The pooled mean platelet count for lung cancer patients was 289×10 9 /L (95% CI: 268 to 311). By subtype, this was 282×10 9 /L (95% CI: 259 to 306) for ADC, 297×10 9 /L (95% CI: 238 to 356) for SCC, 290×10 9 /L (95% CI: 176 to 404) for LCC, and 293×10 9 /L (95% CI: 244 to 342) for SCLC. There was no difference in thrombocytosis prevalence (p=0.76) or mean platelet count (p=0.96) across the subtypes. Conclusion We report no evidence of differences in platelet levels across the major subtypes of lung cancer. A high platelet level is likely to be generic across all lung cancer subtypes. KEY MESSAGES What is the key question? Which (if any) subtype(s) of lung cancer are more associated with thrombocytosis? What is the bottom line? This can facilitate lung cancer diagnostics and provide insights into the biological mechanism between lung cancer and thrombocytosis. Why read on? This is the first systematic review to compare platelet count across different subtypes of lung cancer, combining data from 9,891 patients across 38 studies.