Single‐drug parenteral estrogen treatment in prostatic cancer: A study of two maintenance‐dose regimens

Treatment of 17 patients with prostatic cancer with 320 mg polyestradiol phosphate (PEP) as intramuscular injections every fourth week suppressed serum testosterone (T) values to orchidectomy levels within 1 month, and serum estradiol‐17β (E 2 ) rose to a mean level of 2,456 pmol/liter after 6 months. Following 6 months of treatment, the PEP dose was reduced to 80 mg/4 weeks in 9 and 160 mg/4 weeks in eight patients. Mean T levels increased significantly after dose reduction in both groups and were above the upper orchidectomy limit at 1 month after dose reduction in the 80 mg group. Mean T levels, however, remained below this level at 5 months in the 160 mg group. Dose reduction caused a rise in gonadotropin levels in the 80 mg but not in the 160 mg group. While 320 mg/4 weeks may be a suitable initial dosage, doses ≪ 160 mg/4 weeks are insufficient as maintenance dosages if orchidectomy values of T are required.