Sperling Prostate Center

A Better PSA Calculation

UPDATE: 11/8/2021
Originally published 7/2/2014

Getting an annual PSA blood test to screen for prostate cancer (PCa) has been likened to playing Russian roulette. You hope to dodge the you’ve-got-prostate-cancer bullet. So far, the search for a 100% accurate liquid biopsy via blood draw or urine test has been as unsuccessful as the hunt for a better mousetrap. Even the novel PSA velocity calculation we presented in our 2014 blog (below) is not a sure-fire way to know if a patient needs a conventional TRUS biopsy—which, by the way, is also not 100% accurate for diagnosing PCa. In fact, as of this writing there does not exist a simple test that alone can accurately detect PCa prior to a biopsy. So, we must turn to a combination approach.

In 2021, expert members of the European Association of Urology (EAU) introduced a “Risk-Adapted Early Detection Strategy for Prostate Cancer”. It’s aimed at “well-informed men based on PSA testing, risk calculators, and multiparametric magnetic resonance imaging, which can differentiate significant from insignificant prostate cancer.”[i] They note that this integration, which still includes PSA screening, avoids the current practices that lead to overdetection and overtreatment of insignificant PCa. It’s also a knock at 2012 USPSTF downgrading of the PSA test for routine screening, which has led to higher rates of initial diagnosis of more aggressive PCa that had time to develop while men stopped getting PSA tests. However, there’s a catch to implementing their strategy: “Education is required among urologists, general practitioners, radiologists, policy makers and healthy men…” Thankfully, our Center has been ahead of the strategy curve as far as introducing mpMRI into the diagnostic pathway following an abnormal PSA result. In fact, based on our mpMRI scans, we also offer real-time MRI-guided in-bore biopsy for precise tumor targeting with the fewest needles to gain the most accurate diagnosis available. We support annual PSA blood tests, flawed as they might be, because together with mpMRI they are still part of a risk-adapted early detection strategy.

 

By now, any discussion of the PSA (prostate specific antigen) blood test is practically old hat. The adage that “tests beget tests” is particularly true for PSA, because it is not specific for cancer. Too many other conditions—even a simple act like riding a bicycle—can bump up the amount of this antigen in the bloodstream. Many doctors still consider an elevated or rising PSA as a red flag, and send patients for a biopsy. And then we get into the problem of biopsies…but don’t get me started!

PSA alone is far from perfect, but it’s not completely hopeless as a communicator. If it begins to rise, and is followed periodically over a year, the velocity (speed) with which it is rising can be a true warning sign.

Authors Stacy Loeb, E. Jeffrey Metter et al published a way to assess cancer risk by assigning “risk values” to PSA progression.[ii] They developed a simple formula for calculating prostate cancer risk based on PSA velocity using a threshold of <0.4 ng/mL rise per year as being zero risk. (This threshold was based on previous studies done by themselves and others, correlated with pathology evidence from prostatectomy specimens.) They defined two points, PSAV1 (the first PSA to “trigger” a tracking period) and PSAV2, the final PSA at diagnosis, with no blood draws closer than 6 months apart. Their population sample size is impressive: 18,214 men from a screening study.  Their work is summarized in this table:

PSA Velocity “Risk Count”

Risk Count

Definition

0

Both PSAV1 and PSAV2 increase less than 0.4 ng/mL per year

1

Either PSAV1 or PSAV2 increase more than 0.4 ng/mL per year

2

Both PSAV1 and PSAV2 increase more than 0.4 ng/mL per year

 

Statistically, they demonstrated that a risk count of 2 indicated 8 times the risk of prostate cancer, with 5.4 greater risk that the patient was harboring Gleason 8-10 cancer.

My feeling is that we’re rapidly approaching more widely used tests for molecular markers that will make PSA testing obsolete. However, with increasing economic pressures to keep medical costs down, in many demographic locations where low income predominates and community physicians don’t have access to more sophisticated technologies, PSA will continue to be of use. Until everyone catches up with the coming tests—and they are affordable—perhaps the scoring system of Loeb et al can play a meaningful part in “red-flagging” PCa before the risk count reaches 2.

NOTE: This content is solely for purposes of information and does not substitute for diagnostic or medical advice. Talk to your doctor if you are experiencing pelvic pain, or have any other health concerns or questions of a personal medical nature.

[i] Van Poppel H, Roobol MJ, Chapple CR, Catto JW et al. Prostate-specific Antigen Testing as Part of a Risk-Adapted Early Detection Strategy for Prostate Cancer: European Association of Urology Position and Recommendations for 2021. Eur Urol. 2021 Aug 15;S0302-2838(21)01927-8.
[ii] Loeb S, Metter EJ, Kan D, Roehl K, Catalona W. Prostate specific antigen velocity risk count improves the specificity of screening for clinically significant prostate cancer. BJUI. 2012 Feb;109(4):508-514.

 

About Dr. Dan Sperling

Dan Sperling, MD, DABR, is a board certified radiologist who is globally recognized as a leader in multiparametric MRI for the detection and diagnosis of a range of disease conditions. As Medical Director of the Sperling Prostate Center, Sperling Medical Group and Sperling Neurosurgery Associates, he and his team are on the leading edge of significant change in medical practice. He is the co-author of the new patient book Redefining Prostate Cancer, and is a contributing author on over 25 published studies. For more information, contact the Sperling Prostate Center.

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