[Prostate specific antigen. Clinical applications of ultrasensitive assay]

Recent progress in the techniques used to assay prostate specific antigen (PSA) have made this diagnostic tool even more useful in the management of patients with cancer of the prostate. However, although "ultrasensitive" methods can now detect minute levels, there still is no widely accepted definition of the detection threshold making it difficult to compare results reported with the different techniques. Ultrasensitive assay is particularly interesting in patients who have had radical prostatectomy, offering complementary information to the pathology examination of the surgical specimen. Used as a tool for following disease course after surgery, ultrasensitive PSA is currently the most sensitive measure of disease recurrence. Ultrasensitive assay can also give an evaluation of the effect of post-surgery complementary radiotherapy. Inversely, it adds no further information compared with regular assay before surgery. Thus, ultrasensitive assay is not indicated for differential diagnosis or screening programmes but is a valuable tool for evaluating the effectiveness of curative surgery or exclusive curative radiotherapy.