Prescriptions for flutamide and bicalutamide

Sir, - I would like some clarification of the following situation. The depot LHRH analogues goserelin and leuprorelin are used in advanced prostate cancer to produce a medical orchidectomy. Additional drugs, the anti-androgens flutamide and bicalutamide may only be prescribed in conjunction with one of the LHRH analogues. This is taken literally, even if a man had undergone earlier bilateral surgical castration. The LHRH analogue is entirely wasted in this setting, which at a cost of $1150 for 3 months seems particularly absurd. I do note that a related drug nilutamide can be used in conjunction with surgical orchidectomy, and wonder why this does not apply to the other two.

Associate Professor Gillian Duchesne
Peter MacCallum Cancer Institute
University of Melbourne
Melbourne, Vic.

The subsidy of these drugs reflects their marketing approval. Bicalutamide and flutamide are registered for the treatment of advanced prostate cancer in combination with GnRH agonist therapy and thus are restricted on the Pharmaceutical Benefits Scheme in the same way. Nilutamide, on the other hand, is registered for the treatment of (previously untreated) metastatic prostatic carcinoma, in conjunction with surgical or medical castration. Consequently, it is listed on the Pharmaceutical Benefits Scheme for use in conjunction with LHRH agonists or orchidectomy.

The Therapeutic Goods Administration comments:

In order for a sponsor company to obtain approval for use of an antiandrogen drug in combination with orchidectomy, the Therapeutic Goods Administration would require evidence from appropriately conducted clinical trials to demonstrate that the use of the drug in combination with orchidectomy is more effective than the use of orchidectomy alone.

The approved indications for the 3 antiandrogen products are based upon the data submitted to date by the 3 sponsoring companies.
The approved product information documents for flutamide and bicalutamide indicate that the submitted data for these drugs support their use in combination with LHRH analogues only in previously untreated patients (i.e. in patients who have not undergone orchidectomy). The approved indications therefore do not imply that the antiandrogen must be used in combination with an LHRH analogue in patients who have undergone surgical castration.