Thrombocytosis as a prognostic factor in inflammatory breast cancer

Platelets are essential components of hemostasis and also play an important role in the tumor microenvironment. The purposes of our research were to examine the role of thrombocytosis in inflammatory breast cancer (IBC) and to know which cytokine drives thrombocytosis. We reviewed the medical records of 3654 patients with stage I-III breast cancer treated between 1998 and 2013, including 230 patients (6%) with IBC. We used Chi-squared test or Fisher's exact test to compare the variables between patients with and without thrombocytosis. Multivariate Cox regression models were used to determine the association of thrombocytosis with overall survival. We also examined baseline serum cytokine levels in 81 patients with primary IBC to determine the association of inflammatory cytokines with thrombocytosis. We found that thrombocytosis was the only variable that predicted prognosis. Fifty-five patients (1.5%) had thrombocytosis. Thrombocytosis was more prevalent in patients with IBC than in those with non-IBC (3.4% vs. 1.4%, p = 0.015). In patients with IBC, thrombocytosis was associated with worse overall survival [hazard ratio 2.38, 95% confidence interval (CI) 1.05-5.4, p = 0.0378]. Circulating levels of growth-regulated oncogene (GRO) (odds ratio 1.003, 95% CI 1.001-1.005, p = 0.0019) and transforming growth factor beta (TGF-beta) (odds ratio 1.3, 95% CI 1.128-1.499, p = 0.0003) were associated with thrombocytosis. Thrombocytosis was more prevalent in patients with IBC than in those with non-IBC and it was associated with poor prognosis. GRO and TGF-beta were associated with thrombocytosis in IBC.