Prospective Study of Estramustine Phosphate for Hormone Refractory Prostate Cancer Patients following Androgen Deprivation Therapy

Abstract

Introduction: Estramustine phosphate (EMP) in combination with other cytotoxic agents has been widely used in clinical trials as an anti-tumor agent for the treatment of hormone-refractory prostate cancer (HRPC). However, few prospective studies have considered the efficacy of EMP monotherapy for HRPC patients following androgen-deprivation therapy (ADT), given the availability of methods to measure prostate-specific antigen (PSA) levels in the serum. We therefore initiated a prospective study to determine whether EMP is efficient for HRPC following ADT using changes in PSA levels as the major endpoint. Methods: After a diagnosis of anti-androgen withdrawal syndrome had been excluded, 34 patients with HRPC who showed an elevated serum PSA level in 3 or more sequential tests following ADT were treated orally with 560 mg/day of EMP. The clinical stage and the median PSA value for inclusion in the study were D2 and 25.9 (range 6.5–540.8) ng/ml, respectively. Treatment was continued until evidence of disease progression reappeared or until severe adverse effects appeared. Results: Of the 34 patients enrolled, 29 were evaluated, while the other 5 (15%) patients were discontinued due to severe gastrointestinal side effects. Seven of the 29 patients (24%) showed a decrease of 50% or greater in serum PSA levels from the initially elevated values, with the median duration of PSA response being 8.0 (range 2.2–18.8) months. Baseline PSA, hemoglobin, alkaline phosphatase, lactate dehydrogenase, performance status, and length of time of initial hormonal treatment did not correlate with the PSA response. With a median follow-up time of 20.0 (range 3.2–45.6) months, the cancer-specific survival rate at 2 years was 83% in the PSA responders and 44% in the non-responders. The PSA response was correlated with cancer-specific survival (p = 0.029). Conclusions: Following ADT one quarter of HRPC patients responded to EMP, with more than 50% of patients showing a decrease in PSA levels and an enhanced survival rate.