Prostate Health Index (phi) Addresses USPSTF Concerns, Provides Better Results
A groundbreaking new prostate cancer screening test – now approved today by the U.S. Food & Drug Administration (FDA) and currently available in Europe and Australia – may change the face of screening through its more accurate readings and reduction of false-positive results.
The new screening test – called the “Prostate Health Index (phi)” – combines the PSA and free PSA with a novel, clipped form of the precursor to PSA, called “-2 pro PSA”. This precursor form of PSA – which is more elevated in prostate cancer patients and more accurately identifies the disease – was jointly discovered by Kevin Slawin, M.D., founder of the Vanguard Urologic Institute and the Texas Prostate Center at Memorial Hermann-Texas Medical Center, and researchers at Beckman Coulter1. Baylor College of Medicine, where Dr. Slawin was Professor and Director of the Baylor Prostate Centerpracticed at the time, licensed the technology2 exclusively to Beckman Coulter, which then developed the new screening test.
Renowned PSA screening expert William Catalona, M.D., recently led a pivotal, multicenter study that confirmed the improved performance of the phi score over the regular PSA or free PSA tests, and published the results in the Journal of Urology. Dr. Slawin also participated in the trial along with other leading prostate cancer researchers, and was a co-author on the published report.
Its approval comes at a critical time with the United States Preventive Services Taskforce’s (USPSTF) recent recommendation against the use of the prostate specific antigen (PSA) blood test to screen healthy men for prostate cancer. Shortly after the FDA first approved the PSA test in 1994, the country saw an abrupt reversal and subsequent 40 percent decrease in the risk of dying from prostate cancer, a disease that remains the second leading cause of cancer deaths in the U.S., claiming the lives of more than 28,000 men each year.
The USPSTF based its divisive decision on the fact that as many as 50 percent of screened patients with an elevated PSA will have a false-positive reading, leading them to undergo unnecessary biopsies. In addition to the potential psychological toll associated with this procedure, these men also face the possibility of severe infection that can occur after biopsy. A significant portion of men diagnosed with low risk, screen-detected prostate cancer may then be treated for a cancer that may not have been life-threatening if left undiagnosed or untreated.
“Despite these challenges, when studied in large, well-performed, randomized clinical trials following patients for ten or more years, PSA-based screening has been shown to reduce death from the disease by as much as 44 percent,” said Dr. Slawin. The large number of passionate proponents and opponents of PSA-based screening has led The New England Journal of Medicine to deem this debate, “the controversy that refuses to die.”
In 1998, the percent-free PSA test was FDA approved for use in men with a PSA score between four and 10, effectively reducing the risk of unnecessary biopsies by roughly 20 percent. Despite extensive efforts since then, until now, no additional, improved, screening test for prostate cancer has received FDA approval.
“The answer to this debate is not to do away with a test that saves lives,” said Dr. Slawin. “It is to build on decades of research on the biology of prostate cancer and the PSA molecule to develop more accurate, dependable screening tools that identify patients whose lives are at stake and would benefit from treatment, while reducing inaccurate readings for healthy men. With this new test, physicians will be better equipped to identify patients more likely to benefit from biopsy, and potentially, from treatment for early prostate cancer.”
Dr. Slawin, who has devoted his career to the study and clinical care of men with prostate cancer, is a pioneer in robotic prostatectomy, which he first performed in 2001. He emphasizes the importance of minimizing the risks of prostate biopsy and reducing the side effects of prostate cancer treatment – two criticisms of screening raised by the USPSTF.
“The FDA approval of phi – based on the discovery of -2 pro PSA – may have reopened the door on effective screening and offers hope to patients who may need treatment for a disease they otherwise wouldn’t know they had,” said Dr. Slawin. “It represents the culmination of years of hard work by leading researchers from around the world and is a significant step forward in the field of prostate cancer screening. It debate and has the potential to help rebalance the scales in favor of toward screening – preventing us from losing the considerable ground we’ve gained since PSA was first introduced.”
1 Mikolajczyk SD, Millar LS, Wang TJ, Rittenhouse HG, Marks LS, Song W, Wheeler TM, and Slawin KM. A precursor form of prostate-specific antigen is more highly elevated in prostate cancer compared with benign transition zone prostate tissue. Cancer Res 2000;60:756-9.
2 U.S. Patent Number: 6,423,503. “Forms of Free Prostate-Specific Antigen (PSA) and their association with prostate tissues from prostate peripheral zone and transition zone”. Inventors: Mikolajczyk SD, Wang TJ, Rittenhouse HG, Wolfert RL, Slawin KM, Issued: July 23, 2002, Assignee: Baylor College of Medicine.