6. Patients receiving anti-androgen agent as part of primary androgen ablation: disease progression after stopping the anti-androgen agent. This disease progression is defined: 2 consecutive increasing PSAs ≥ 2 weeks apart, or documented osseous or soft tissue progression. Flutamide patients: at least one of the PSAs ≥ 4 weeks after stopping flutamide. Bicalutamide or nilutamide patients: at least one PSA ≥ 6 weeks after stopping the anti-androgen agent.