Progression of prostate cancer despite an extremely low serum level of prostate-specific antigen

A 61-year-old man who had been diagnosed with prostate cancer 9 years ago and had been treated with pelvic irradiation and intermittent androgen deprivation therapy visited the emergency room because of back pain and weakness in both legs. Spine magnetic resonance imaging showed a lumbar epidural mass and spine metastasis. The whole-body workup revealed multiple metastases to the lymph nodes, bone, liver, and lung. The serum prostate-specific antigen was 0.02 ng/ml. He underwent laminectomy, posterior fixation, and epidural mass excision, and metastatic adenocarcinoma from the prostate was diagnosed. The patient underwent 1 cycle of docetaxel-based chemotherapy. More chemotherapy could not be done because of his general weakness. The patient died one month later of multiple organ failure.