Withdrawal phenomenon with the antiandrogen casodex.

Total androgen blockade with castration and antiandrogens has become the primary therapy in metastatic prostate carcinoma. Several reports have been published on the flutamide withdrawal syndrome with a favorable response in patients with progression of disease after lengthy remission while taking combined hormone therapy. The experience with withdrawal of the experimental nonsteroidal antiandrogen casodex in 3 patients is reported. All patients received casodex monotherapy initially, then luteinizing hormone-releasing hormone analogues were added on progression of disease (bone scan and prostate specific antigen [PSA]) and eventually casodex was withdrawn on further progression of disease (PSA and bone scan). Two patients had declines in PSA levels of 42% and 75% sustained for 3 to 6 months, and 1 patient had a stable condition for 2 months. These responses were similar to those of withdrawal of flutamide, which were limited to patients who had received combination therapy at the onset of treatment. Thus, the observations in this report would suggest that the initial and sustained exposure to an antiandrogen is the more important factor in the withdrawal phenomenon rather than the low androgen environment alone that occurs with initial luteinizing hormone-releasing hormone analogue monotherapy, orchiectomy or combination luteinizing hormone-releasing hormone analogue and antiandrogen.