[Secondary endocrine therapy with oral estrogen for relapsed prostate cancer]

We report clinical outcomes of secondary endocrine therapy with oral estrogen for relapsed prostate cancer. A total of 18 patients were treated with oral estrogen as a secondary endocrine therapy for relapsed prostate cancer between February 2002 and December 2007. One mg/day of ethinylestradiol was administered orally and the dose was increased to 3 mg/day if necessary. A decrease of serum prostate specific antigen (PSA) level was seen in all of the 15 patients who were able to take ethinylestradiol without severe side effects. The PSA level was decreased more than 50% in 11 out of 15 (73.3%) patients. Median re-relapse-free survival was 15 (3-32) months. This effectiveness was as good as intravenous high-dose diethylstilbestrol diphosphate (DES-DP) treatment which was used as a secondary endocrine therapy for relapsed prostate cancer at our institute previously. Oral administration of ethinylestradiol is effective and outpatients can be treated at a low cost, so it should be considered as one of the treatment options for relapsed prostate cancer after initial endocrine therapy.