Undetectable serum prostate-specific antigen associated with metastatic prostate cancer: a case report and review of the literature.

A 63-year-old man, who had undergone prostatectomy for prostate cancer that was positive for prostate-specific antigen (PSA) was examined and found to have metastatic disease, proven radiologically and pathologically, but with an undetectable PSA and highly elevated prostatic acid phosphatase (PAP). Prostatic acid phosphatase levels fell in response to chemotherapy but his clinical status continued to deteriorate. A review of the literature is presented and several possible explanations for PSA remaining undetectable in these situations are discussed. The authors conclude that although PSA can be used to monitor the majority of patients postprostatectomy, physicians may still need to rely on clinical suspicion, serum PAP, and bone scan for the detection of recurrent disease.