New Prostate Cancer Study Affirms Value of PSA Test
Refuting Proposed 'End of the PSA Era,' Research Finds PSA Still Accurately Predicts Cancer Recurrence
May 23, 2005
Refuting recent claims that the era of the prostate-specific antigen (PSA) test is over, physician-scientists at Columbia University Medical Center and NewYork-Presbyterian Hospital presented a study demonstrating that pre-operative PSA is an accurate measure of cancer recurrence. The study was presented today at the annual meeting of the American Urological Association (AUA) in San Antonio, Texas.
In a statistical analysis of 1,246 NewYork-Presbyterian/Columbia prostate cancer patients who underwent radical retropubic prostatectomy (RRP) – removal of the prostate – with no adjuvant therapy between 1988 and 2003, investigators found that, when controlling for cancer stage and grade (Gleason sum and pathologic stage), pre-operative PSA is an accurate predictor of biochemical failure (BCF) (a measure of cancer recurrence defined as PSA ≤ 0.2µg/ml), with the same degree of accuracy – irregardless of when the RRP was performed. This follows research presented at the 2004 AUA meeting by Dr. Thomas Stamey of Stanford University which found that PSA does not correlate with the amount of cancer that recurs following prostatectomy, but instead to prostate size – leading speculation about the continued predictive powers of PSA.
"Contrary to other recent interpretations, our analysis finds that PSA remains a vital tool for determining risk of recurrence in prostate cancer patients – indeed, the predictive ability of the PSA test does not significantly vary over the last 15 years," says Dr. Mitchell C. Benson, director of urologic oncology at NewYork-Presbyterian/Columbia and interim chairman of the department of urology and George F. Cahill Professor of Urology at Columbia University College of Physicians and Surgeons.
Investigators found that, when controlling for cancer stage and grade, there has been no significant change in the impact of PSA in predicting BCF. Researchers controlled for stage and grade because these two variables, with PSA, are used to predict outcome after surgery. Using a concordance index, the accuracy of PSA in predicting outcome, stratified by time period in which the procedure was performed, are statistically equivalent: .65 for the period 1988-1993, .66 for the period 1994-1998, and .64 for the period 1999-2003.
Surprise Finding: Prostatectomy More Effective In Preventing Cancer Recurrence Today, Even When Controlling for PSA Level
Prostate cancer patients who undergo radical prostatectomy today are less likely to have cancer recurrence than patients 15 years ago, even when controlling for PSA levels, according to a second Columbia University Medical Center and NewYork-Presbyterian Hospital study. Using the same data as the first study and controlling for PSA, researchers found that patients who had the procedure in the years 1999-2003 and 1994-1998 were less likely to have cancer recurrence (defined as biochemical failure), when compared to patients who had the procedure in the years 1988-1993 – with hazard ratios of 0.583 and 0.576, respectively. The study will be presented at an AUA poster session on Wednesday, May 25.
"It is well known that since the PSA test was first introduced in 1988-1989, patients have presented with an earlier-stage cancer, with lower PSA (a trend dubbed "PSA migration"), which leads to decreased recurrence. Surprisingly, we found that, even after we controlled for this change in initial PSA level, recurrence is still less likely to occur in recent years, compared to earlier years," says Dr. James McKiernan, assistant attending urologist at NewYork-Presbyterian/Columbia and assistant professor of urology at Columbia University College of Physicians and Surgeons.
Neither age, nor the surgery's ability to get rid of the cancer (a measure known as surgical margin status) explains this finding. Specific factors that account for this change in outcomes over time have yet to be identified, according to the study authors, but may include prostate cancer tumor volume upon initial presentation.
Prostate-specific antigen (PSA) is a protein produced by the cells of the prostate gland. High levels of PSA indicate the presence of a cancer. The test measures the level of PSA in the blood. Additional tools, including biopsy, are used to make a diagnosis of prostate cancer.
The PSA blood test has made a major impact in helping diagnosis and counseling patients on risk of cancer recurrence post-surgery. Since the dawn of the PSA era, the number of patients who have caught their prostate cancer early has risen dramatically.
The two studies will be presented by Robert Mitchell, a fourth year medical student at Columbia University College of Physicians and Surgeons and fellow in the Department of Urology at NewYork-Presbyterian/Columbia, and Dr. Jay B. Shah a resident in the in the Department of Urology at NewYork-Presbyterian/Columbia. Additional Columbia University Medical Center and NewYork-Presbyterian physician-scientists who co-authored the studies include Drs. Manisha Desai, Eric T. Goluboff, Aaron E. Katz, and Carl A. Olsson.
New York-Presbyterian Hospital is the largest not-for-profit, non-sectarian hospital in the country. It provides state-of-the art inpatient, ambulatory and preventive care in all areas of medicine at five major centers: New York-Presbyterian hospital/Columbia University Medical Center, New York-Presbyterian Hospital/Weill Cornell Medical Center, Children's Hospital of New York-Presbyterian, the Allen Pavilion, and the Westchester Division. It consistently ranks as one of the top hospitals in the country in U.S.News & World Report's guide to "America's Best Hospitals." The New York-Presbyterian Healthcare System – an affiliation of acute-care and community hospitals, long-term care facilities, ambulatory sites, and specialty institutes – serves one in four patients in the New York metropolitan area.
Columbia University Medical Center provides international leadership in basic, pre-clinical and clinical research, medical education, and health care. The medical center trains future leaders in health care and includes the dedicated work of many physicians, scientists, nurses, dentists, and other health professionals at the College of Physicians & Surgeons, the School of Dental & Oral Surgery, the School of Nursing, the Mailman School of Public Health, the biomedical departments of the Graduate School of Arts and Sciences, and allied research centers and institutions. With a strong history of some of the most important advances and discoveries in health care, its researchers are leading the development of novel therapies and advances to address a wide range of health conditions.