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Prostate-specific antigen (PSA) testing has a complex role in prostate cancer diagnosis. On the one hand, it can help identify early prostate cancer. On the other, routine PSA screening can lead men to have biopsies or invasive treatments they may not need.

This has caused the medical community to re-evaluate how best to use the PSA test.

"While men in their 40s should begin a dialogue with their doctor about the pros and cons of PSA screening through middle age, work is ongoing to achieve the ultimate goal: developing a screening regimen that identifies only the prostate cancers that need to be cured," says Dr. Mark Pomerantz, an oncologist with Harvard-affiliated Dana-Farber Cancer Institute. "And there is a way for PSA testing to help achieve this."

The ABCs of PSA

PSA is a chemical made by the prostate. A PSA test measures the amount in a man's blood. A PSA level of less than 4 nanograms per milliliter (ng/mL) is considered normal.

"Though there is no level below 4 that guarantees freedom from prostate cancer, a level higher than 4 is the conventional threshold for considering a biopsy to look for cancer," says Dr. Pomerantz.

The PSA test initially was developed for use in men already diagnosed with prostate cancer and undergoing treatment, and it's highly reliable in this regard. PSA levels can reveal whether cancer has returned after surgery or whether the tumors have grown or shrunk after treatment with hormones or radiation.

But decades ago, research showed that in men not known to have prostate cancer, PSA levels higher than 10 ng/mL often indicated the presence of the disease. Soon after, it became the go-to prostate cancer screening test. However, PSA screening is far from perfect, especially when a man's level is between 4 ng/mL and 10 ng/mL.

These somewhat higher PSA levels frequently happen for reasons other than cancer, such as a benign enlarged prostate, an inflamed prostate (prostatitis), bike riding, or recent ejaculation. A man with this screening result often ends up proceeding with a biopsy — an invasive procedure with its own potential complications — just in case cancer is present.

And even when a biopsy confirms that cancer is the source of a rising PSA level, many men end up undergoing treatment for low-risk, slow-growing cancer that might never affect their longevity or quality of life.

"Treatments like surgery and radiation, beyond the stress and invasiveness associated with the procedures, also involve possible side effects like incontinence and erectile dysfunction," says Dr. Pomerantz.

In addition, research has produced mixed results on whether regular PSA screening helps men in the long run. "Even after 30-plus years of using the PSA test for screening, it still isn't clear how well it prevents prostate cancer deaths," says Dr. Pomerantz. "And the reality is that even among men with prostate cancer, most will die from something else."

The main problem with using PSA tests to find prostate cancer? Most older men already have some traces of the cancer.

"You could take 100 random middle age or older men off the street, examine their prostates, and more than half would probably have some low-risk cancer, even though they may be healthy and unaffected by it for life," says Dr. Pomerantz. "If you go snooping around for prostate cancer, you will find it."

Better ways to use testing

So the question has become this: what role does PSA testing now play in prostate cancer screening?

"The result of a PSA test no longer needs to be the final word in who does or doesn't get a biopsy," says Dr. Pomerantz. "Men now have other ways to check for cancer that can minimize the need for invasive biopsy."

For example, if a PSA test suggests possible cancer, doctors now can order magnetic resonance imaging (MRI) of the prostate. The technology produces a high-resolution image of the entire prostate gland. Cancerous tissue has different magnetic properties than normal tissue, and an MRI scan can capture these differences.

If MRI reveals no cancer, your doctor may recommend you continue to monitor your prostate with PSA testing. If the scan does show the possibility of cancer, the detailed image can help the doctor determine the tumor's size and which part of the prostate should be sampled with a biopsy.

"This targeted approach can help with a more accurate diagnosis and avoid the need for repeated biopsies," says Dr. Pomerantz. "It brings us closer to our goal in prostate cancer screening — reliably finding the aggressive prostate cancers and avoiding overdiagnosis."

Another role for PSA testing

Periodic PSA testing is regularly used during active surveillance, a wait-and-see approach to prostate cancer management in which men monitor their cancer for changes and explore treatment options only if it becomes more active.

"The monitoring approach of active surveillance is ideal for many men diagnosed with low-risk cancer," says Dr. Pomerantz.

After an initial biopsy, active surveillance involves more frequent PSA testing to look for any changes. If your PSA level increases, your doctor may order an MRI scan to determine whether a repeat biopsy is needed.

"In this way, PSA tests can help men better monitor their condition and avoid jumping into treatment," says Dr. Pomerantz. "It can help men feel proactive about managing their prostate cancer."

Image: © Jose Luis Pelaez Inc/Blend Images LLC/Getty Images