A spotlight from prostate cancer.

Serum prostate-specific antigen (PSA) levels are used to monitor the development of prostate cancer, recurrence after surgery, and response to subsequent therapy. However, the clinical implications often are difficult to interpret. Ulmert and colleagues report use of a positron-emitting labeled monoclonal antibody directed to a unique PSA epitope to noninvasively image PSA-positive prostate cancer xenografts and to measure both androgen-stimulated PSA expression and androgen therapy-responsive PSA decreases.