From the Research
Bicalutamide (Casodex) is unlikely to significantly reduce Prostate-Specific Antigen (PSA) levels after just 3 days of treatment. While bicalutamide is an effective antiandrogen medication used in prostate cancer treatment, PSA reductions typically require more time to become clinically significant. Most patients will need to take bicalutamide (standard dose of 50mg daily when combined with LHRH therapy, or 150mg daily as monotherapy) for at least 2-4 weeks before seeing meaningful PSA decreases. This timing reflects the medication's mechanism of action, which works by blocking androgen receptors in prostate tissue, gradually reducing androgen-dependent cellular activity and PSA production. The full effect on PSA levels often takes 3-6 months of continuous treatment.
Some key points to consider:
- Bicalutamide has a long plasma elimination half-life of about 1 week, which allows for once-daily dosing 1.
- The medication's efficacy in reducing PSA levels has been demonstrated in several studies, including a phase II multicenter trial where 59% of patients had a > 90% decrease in PSA levels or a decline to < 4 ng/mL 2.
- However, the timing of PSA reductions can vary, and some patients may experience a rapid rise in PSA levels after starting bicalutamide, possibly due to an early agonist activation of androgen receptor by bicalutamide 3.
- Regular PSA monitoring at appropriate intervals (typically monthly initially, then quarterly) is important to properly assess the medication's impact over time.
Patients should continue taking the medication as prescribed and understand that early PSA measurements after starting bicalutamide may not reflect the treatment's ultimate effectiveness. As noted in a review of bicalutamide in advanced prostate cancer, the medication has a good tolerability profile and is an attractive option when combined with a GnRH agonist in patients with advanced prostate cancer who are suitable to receive MAB regimens 4.