Long-term complete response of antiandrogen withdrawal syndrome in a patient with metastatic prostate cancer: A case report.

Antiandrogen withdrawal syndrome (AWS) is a well-established phenomenon in prostate cancer treated with combined androgen blockade (CAB). AWS is generally defined as subjective and/or objective improvement following discontinuation of an antiandrogen. However, the duration of the AWS response is usually limited. In addition, a complete response is quite rare. We herein present the case of a patient who achieved complete response from AWS, with the duration of this response lasting for >6 years. A 72-year-old man with metastatic prostate cancer received CAB with a luteinizing hormone-releasing hormone analog and bicalutamide. In addition, for local cancer control, external beam radiation therapy (70 Gy) to the prostate was performed. Subsequently, the serum prostate-specific antigen (PSA) level reached a nadir (undetectable level). Four years later, the patient's serum PSA level started to rise, and bicalutamide was discontinued to confirm AWS at a serum PSA level of 0.34 ng/ml. The PSA level immediately decreased again to an undetectable level (0.00 ng/ml), where it has been remained for 6 years. Bone scintigraphy and computed tomography scans have shown no evidence of bone or other metastases since the introduction of AWS. To the best of our knowledge, there have been no reports of such a long duration of complete response from AWS. Therefore, this phenomenon should always be considered, even in patients with advanced disease.