17β-estradiol-mediated elevation of peripheral white blood cell count observed during estramustine phosphate therapy for prostate cancer

Background: in 1983, daponte et al. first reported an increase in the peripheral white blood cell (wbcs) counts of prostate cancer patients treated with estramustine phosphate (emp) therapy.objectives: in order to confirm daponte’s observation, we reviewed the clinical data of prostate cancer patients treated with emp. we also examined the association between wbc counts and 17β-estradiol levels throughout the duration of the emp therapy.patients and methods: the study population comprised of 66 prostate cancer patients who were being treated with emp. the complete blood count with a differential wbc count and the levels of serum 17β-estradiol and c-reactive protein measured during the therapy were compared with the baseline levels. the correlation between serum 17β-estradiol level and wbc count was calculated using the pearson correlation test.results: we observed that the total wbc and the neutrophil counts were significantly elevated during the therapy. the serum 17β-estradiol level significantly correlated with the wbc count (r2 = 0.031, p = 0.002). the granulocyte colony-stimulating factor levels measured during therapy were approximately 2-fold higher than the upper limit and decreased after cessation of the treatment (p = 0.037).conclusions: we successfully confirmed daponte’s observation. the increase in wbc counts was possibly attributable to elevated serum 17β-estradiol levels.