Patients with prostate cancer may experience a decrease in PSA levels if they stop taking anti-androgen medication when prostate-specific antigen (PSA) levels gradually increase during anti-androgen therapy, a phenomenon called “anti-androgen withdrawal syndrome.
It was first observed with flutamide and later in patients treated with other androgen medications such as bicalutamide, chlormadinone acetate, megestrol acetate, and hexestrol.
In patients with prostate cancer treated with anti-androgen therapy, the presence of elevated PSA levels means that the prostate cancer will enter the androgen non-dependent phase.
Once this occurs, the first step your doctor should take is to stop the anti-androgen medication and watch for an anti-androgen withdrawal syndrome, which does improve in some patients, but the duration of the decline in PSA levels after stopping the medication varies. If no withdrawal effect is observed, try switching to another anti-androgen drug.