Summary

Platelet count has been reported to have predictive value invarious cancer entities. In the case of breast cancer, evidenceabout involvement of platelets is still incomplete. Our objectivewas to assess the influence of pretreatment thrombocytosis onsurvival and establish its prognostic relevance for breast cancerpatients.We performed a retrospective, multivariate analysis of 4,300patients with early-stage breast cancer. All subjects participatedin one of five prospective, randomized, multicenter trials conductedby the Austrian Breast and Colorectal Cancer StudyGroup. Thrombocytosis was defined as a platelet countexceeding 400 G/L. Median follow-up was 52 months.Univariate and multiple Cox regression models were calculatedfor overall survival (OS), breast cancer-related survival anddisease-free survival (DFS). Pretreatment thrombocytosis was observed in 161 patients(3.7%). Estimated median OS, breast cancer-related survival andDFS for patients with versus those without thrombocytosiswas 71.0 versus 99.5, 72.0 versus 100.9, and 80.4 versus 88.4months, respectively (p = 0.0054, p = 0.0095, p = 0.0199).A multiple Cox regression model including tumor and nodalstatus, grading, age, hormone receptor status and pretreatmentthrombocytosis identified pretreatment thrombocytosis as anindependent predictive factor for OS (p = 0.0064) and breastcancer-related survival (p = 0.0162). Multivariate analysis failedto identify pretreatment thrombocytosis as an independent riskfactor for DFS (p = 0.1355).In our retrospective study, elevated platelet counts at time ofdiagnosis were associated with poor prognosis in breast cancer.We hypothesize that platelets may contribute to the pathophysiologyof hematogenous metastasis.