Background: An association was shown between thrombocytosis and future development of several cancers.

Objectives: To investigate whether pre-treatment platelet counts correlated with clinical outcomes of patients with breast cancer.

Methods: This retrospective study included 22 patients who had been diagnosed with stage I breast cancer and were 66.8 ± 13.2 years of age. Of these, 22 with stage II were 61.6 ± 12.3 years old and 9 with stage III and IV were 64.4 ± 15.3 years old. Clinical and hematological data from the first visit to the oncology clinic were collected. The follow-up period was 12 months to 5 years.

Results: A significant difference in platelet counts was found between patients who died (187,000 ± 4000 µ/L) and those who were disease free for 5 years (248,000 ± 83,000 µ/L, P = 0.0001). A significant difference in platelet-to-lymphocyte ratio was found between patients who died and those with recurrence (192 ± 81 vs. 124 ± 71, P = 0.01). A negative correlation was found between age and lymph nodes (Ps = -0.305, P = 0.02) and staging and white blood cells count (Ps = -0.280, P = 0.04). A positive correlation was found between clinical staging and lymph nodes (Ps = 0.443, P = 0.001) and clinical staging and metastases (P = 0.308, P = 0.02).

Conclusions: Platelet counts may be a prognostic marker for breast cancer. Patients who died within 1 year had lower pre-treatment platelet count, which could represent an insidious disseminated intravascular coagulopathy cancer related consumption process.