Prolonged prostate-specific antigen response in flutamide withdrawal syndrome despite disease progression.

Flutamide withdrawal syndrome is characterized by a decrease in prostate-specific antigen (PSA) after flutamide withdrawal in a subset of patients with progressing metastatic carcinoma of the prostate. It is generally hypothesized to be due to a point mutation in the androgen receptor that allows the antiandrogen to function as an agonist, leading to a dramatic and rapid PSA response. We describe a patient with androgen-independent prostate cancer in whom PSA continued to decrease for a period of 15 months after flutamide withdrawal. With continuing fall in PSA, the patient had unequivocal progression of disease seen on bone scan. This case illustrates the potential decoupling of PSA response from disease status in flutamide withdrawal. It also illustrates the need for continued clinical evaluation of patients with metastatic prostate cancer, even in the face of PSA response.