PSA test isn't perfect

Originally published in The Ottawa Citizen August 5, 2003
Original Title: BPH, PRCa, PSA:What’s the deal?

CJOH anchor Max Keeping’s selfless revelation about his prostate cancer has renewed interest in prostate disease and PSA testing. His announcement came the day after a group called Early Prostate Cancer Diagnosis launched a campaign geared at getting OHIP to pay for an the early screening called the prostate-specific antigen (PSA) blood test for all men over 40.

As it stands, the province will fund PSA tests for men who have already been diagnosed with prostate cancer and those who already have symptoms.

But diagnosing prostate cancer is sometimes no simple matter, even with the PSA test. Is it worthwhile to find the $25 in your own pocket for the peace of mind?

One thing that make prostate cancer hard to diagnose is that it has symptoms similar to those of other conditions, including benign prostatic hypertrophy (BPH), which usually starts after the age of 50.

This enlargement of the prostate gland can cause significant discomfort and potential bladder damage. The prostate increases in size in eight per cent of men aged 31 to 40, in 40 to 50 per cent of men aged 51 to 60, and over 80 per cent of men older than 80 years of age.

If you are a man and live to a ripe old age, chances are good you will get prostate cancer. You’re also very likely to survive it.

Autopsy studies show 10 per cent of men over 50 had prostate cancer, while 70 per cent of men over 80 had it. Ten per cent of prostate cancer is inherited. One in nine Canadian men will get prostate cancer and one in 29 will die of it.

The symptoms of BPH and prostate cancer slowly develop over years. The signs include getting up more frequently at night to urinate, needing to void after urinating, waiting longer for urinary flow to begin, dribbling after urination, urinating more often during the day and a slower, less forceful and sputtering urinary stream.

BPH and prostate cancer have the potential to obstruct the bladder’s efforts to empty. Urine accumulates and distends the bladder walls, which can permanently damage bladder function. It loses the ability to contract and expel the urine.

But other disorders can also be at fault, including a narrowing of the urethra (the tube running from the bladder to the tip of the penis) or the bladder outlet, bladder cancer, bladder stones, urinary tract and prostate infections, or poor nervous system control of the bladder.

A thorough medical history of urinary difficulties, nerve damage or disease, bloody urine, trauma to the urethra and medication use helps point the way to a specific diagnosis.

Rectal examinations will help assess prostate size and consistency among other characteristics and differentiate between benign versus malignant disease.

Several other tests will complement the evaluation, ranging from a simple urine test for blood and infection to more invasive procedures.

A common imaging test, a transrectal prostatic ultrasound, will determine the size of the gland, its consistency and if there are suspicious areas for prostate cancer.

Other tests will measure how well the bladder functions. If there is a clinical suspicion of prostate cancer, a prostate biopsy would be the next step.

BPH treatment involves lifelong medical therapy and, depending upon the clinical situation, surgery to remove part or all of the gland.

Prostate cancer treatment includes a combination of chemotherapy, surgery and radiation therapy. Early detection is essential.

There is contradictory and confusing information about the PSA test. Still, it remains a valuable tool especially for certain clinical conditions, race and age groups.

PSA is a protein produced by the prostate gland. Most of it is attached to other blood proteins, but some floats freely in the blood stream, not bound to other substances.

This unbound type, “free” PSA, is low in men with prostate cancer and high in men with BPH. The serum PSA test adds the bound and free PSA levels together.

PSA levels increase with gland enlargement. The test can be used as a cancer-screening tool for men between 50 and 69 years of age because of the predictable slow and steady growth of the gland and PSA values.

However, the PSA test has limitations, in part because of other influences on the prostate gland. Irritation, ejaculation, infection, obstruction of the urethra and direct pressure (from a rectal exam or anal intercourse) will pump more PSA into the bloodstream, artificially elevating the result.

Men over the age of 69 tend to have more rapid enlargement of the prostate and increasing PSA levels. The results must be interpreted according to age and race-based normal values. Failure to do so could lead to false positive or negative results.

The widely used cut-off serum PSA value of four nanograms per millilitre, an indicator for the suspicion of prostate cancer, remains controversial.

Recent evidence indicates lesser values being associated with cancer. In three studies of men aged 50 and older, 148 of 597 men without prostate cancer (25 per cent) had a PSA value of four or higher. And 136 of 319 men with prostate cancer (43 per cent) had values below four.

A “free” PSA test — a variant of the PSA test — might improve cancer-screening evaluation. This test measures the individual concentration of the total PSA and free PSA. The total PSA level must be more than four in order for this test, combined with the patient’s age, to differentiate BPH from prostate cancer.

To date, the evidence indicates a combination of digital rectal examination and serum PSA testing is the best available means to exclude prostate cancer. The recommendation is to start screening for prostate cancer by age 50 with a rectal exam and PSA.

Family history might result in earlier testing, say, at around age 40. Given the evidence that this is the best we have so far, it stands to reason to give men any opportunity to prevent the disease.

Every other test we have that is covered by OHIP has no age restriction. I do not think PSA should be subjected to this rule. The decision for the test is based on clinical interpretation of the facts and in the best interest of the patient. There must be consistency in the system.


© Dr. Barry Dworkin 2003

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