PSA Progress
Prostate cancer (PCa) remains the second leading cause of cancer deaths in the U.S. as in most Western societies. Most men with PCa will not die from the disease but with it. Since the mid-1980s, screening with the prostate-specific antigen (PSA) blood test has more than doubled the risk of a prostate cancer diagnosis. A decrease in prostate cancer death rates has been observed since that time, but the relative contribution of PSA testing as opposed to other factors, such as improved treatment, has been uncertain. The recent release of two large randomized trials suggests that if there is a benefit of screening with PSA, it is, at best, small.
Most men who succumb to PCa despite hormone treatments suffer what is known as hormone-refractory prostate cancer. Monitoring patients treated with hormones often proves clinically difficult due to conflicting data from serum levels of PSA, symptoms and bone scans. Recently a new marker has been issued FDA clearance – enumerating circulating tumor cells. Patients with an ‘unfavorable’ pretreatment level of CTCs had a shorter overall survival than those who CTC count was favorable – 11.5 vs. 21.7 months. This test may assist the clinician in predicting a prognosis and monitoring therapy and may aid in testing new drugs.
Another possible marker is PCA3 a gene discovered in 1999. Because of its differential expression between prostate cancer and non-neoplastic tissue, several studies have evaluated its value in PCa diagnosis. These papers are consistent with significant statistical accuracy of measure of the urinary number of PCA3 copies. While the sensitivity of PCA3 is slightly less than that of serum PSA, specificity as well as positive and negative predictive values are quite a bit better.