Diagnosing prostate cancer: the PSA testing debate
PSA testing, a major factor in prostate cancer diagnosis, is my chosen topic for this, the third blog of the 30 that I have pledged to publish this November, a.k.a. Movember, the prostate cancer charity for which I am trying to raise money.
PSA testing is a major factor in prostate cancer diagnosis, but it is also hotly debated when governments look at how they should respond to the rising tide of prostate cancer cases (a trend discussed and documented in yesterday's Movember post: Prostate cancer by the numbers).
After explaining what PSA testing is and how it is used, I will explain why some people believe PSA testing can be harmful. Not long ago, one of those people complained when I recommended PSA testing on social media. I took that seriously, investigated the claim, and decided it was groundless. To be clear, this is my position:
What is PSA?
So let's take a look at the role of PSA — Prostate Specific Antigen — and the tests that measure it. Those tests are performed by taking a sample of your blood. This is done with a needle and vial like other blood tests such as a Full Blood Count, or tests for cholesterol levels and liver function.
PSA is a protein manufactured almost exclusively by the prostate gland. The role of PSA is to produce enzymes that keep semen fluid. Under healthy conditions, the cellular barriers of your prostate keep most of this protein locked inside the gland, allowing only a tiny, baseline amount to drift into the bloodstream.
This is why everyone who has a prostate, even one like mine that has been repeatedly blasted by a photon beam, will have some amount of PSA in their blood. I currently have 0.5 ng/mL (half a nanogram of PSA per milliliter of blood). However, I am on medication that reduces PSA, something I will get into in a future post.
For a healthy young man a PSA score of 1.0 ng/mL or less is likely. As men age, more PSA tends to leak, so that PSA number may get up to 2.0 by the time you are in your 40s, without any cause for concern. The "nothing to worry about number" continues to rise over time, but a PSA of 4.0 in anyone under 60 will typically lead to further investigation. (See the disclaimer regarding "typical" at the end of this post: every person is different and there are multiple factors involved in prostate cancer diagnosis other than PSA test results.)
Because the prostate constantly releases small amounts of PSA into the bloodstream, a low level is normal. However, when your prostate is disrupted those cellular barriers become leaky. Those leaks allow PSA to spill directly into the blood and raise your PSA score.
There are numerous things that can cause this leak-inducing disruption of your prostate: inflammation: natural aging and enlargement, or the structural disorganization caused by cancer cells. In other words, the level of PSA in your blood is not a direct indicator of cancer, and it can rise with age without implying you have cancer.
To reiterate, a high PSA score is not a definitive diagnosis for cancer. Non-cancerous conditions—such as benign prostatic hyperplasia (BPH) or a urinary tract infection—frequently cause elevated PSA levels. Basically, doctors use the PSA result as an initial screening tool to determine if further evaluation is necessary.
Back in 2020, I told my GP I was getting up several times a night to pee. I was 68 at the time. He sent me to a urologist who used his finger to check the size of my prostate. It was fairly normal for my age. Because an enlarged prostate can cause PSA to leak, but mine was not enlarged, the urologist ordered a PSA test to see if cancer was involved.
The result was 5.0. That was cause for concern, so a second test was ordered. That was lower, 4.2, but it was still cause for concern because, by then, the urologist was aware that my brother had a serious case of prostate cancer. Apparently, prostate cancer in your blood relatives increases the probability that you might have it too. (There will be a post about the genetics of prostate cancer later in this series.)
PSA misconceptions
When I recommended PSA testing in a recent social media post I got this pushback: "PSA is not a reliable cancer indicator." The commenter also implied that PSA testing could be harmful. These responses embody the two main "beliefs" I see in public discourse about PSA tests:
A: PSA tests are no good.
B: PSA tests can lead to harm.
So let me address these, briefly and then in more detail.
Belief A is technically correct. As you now know from this article: a single PSA result is not a reliable diagnostic test for prostate cancer; however, multiple PSA tests over time are a very valuable indicator of prostate health relative to cancer. A man who gets a PSA test when he turns 40, then annually after that, is much better placed to notice changes that might be an early indicator of prostate cancer, worthy of further investigation.
The source of belief A is the fact that the PSA test is prostate-specific, not cancer-specific. That means levels can rise because of benign enlargement, infection, inflammation, recent ejaculation, and normal biological variation (I scored a 5 and then had several lower scores).
However, the value of PSA becomes substantially greater when it is measured repeatedly over time. A persistent elevation or an upward trend—considered alongside age, prostate volume, family history and other risk factors—can provide a strong signal that further investigation is warranted. The UK guidelines specifically recognise PSA velocity and PSA density as factors that can justify further investigation, while European guidelines recommend repeating a moderately elevated PSA before proceeding further.
Belief B, that PSA tests can lead to harm, is bogus because there is no harm in a PSA test at all, unless there are serious deficiencies in the medical system where the man is tested. Decades ago an abnormal PSA score could lead to a biopsy, which carries risks of harm (which I talk about here). These days, a high PSA score rarely leads straight to biopsy.
A scan of some form is done before biopsy and only if that indicates cancer might be present does a biopsy get scheduled. As in my case, an initial score of 5 only led to a repeated test. Only after a second test and family history did biopsy enter the picture, but that was preceded by scanning.
In modern UK practice, a multiparametric MRI is normally the first line of investigation for suspected localised prostate cancer. The national guidelines explicitly advise against offering biopsy on PSA alone, and men with a low-risk MRI may avoid biopsy altogether. When biopsy is indicated, MRI can identify suspicious areas and permit more targeted sampling.
Consequently, properly conducted PSA testing—with informed counselling and an MRI-led diagnostic pathway—carries little direct physical risk. Psychological harms such as anxiety and overdiagnosis remain possible, but these can be substantially reduced by appropriate explanation, repeat testing, and selective use of imaging and biopsy.
I hope this information has been helpful. I will be looking at PSA testing in a future post when I address the arguments about prostate cancer screening.
Disclaimer: This article was not written by a medical professional and should not be used as the basis for any medical decisions. Please consult a medical professional before taking any medical action as a result of reading this article. Every person's biological characteristics are unique, as are their genes and their personal circumstances. Similarly, every case of prostate cancer is different. While talking about "typical" cases and scenarios can be useful for presenting information, it does not establish any facts or diagnosis or prognosis specific to you or anyone else.
