The Problem With PSA Screening for Prostate Cancer

Doctor using digital tablet to talk to senior man
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There is a real danger that PSA screening will lead to overtreatment. The government, having studied this situation, has therefore recommended dropping PSA screening altogether. This proposal doesn’t seem so ludicrous when you consider the present system is over diagnosing 100,000 men with low-grade disease every year. Studies show that 70,000 of these men naively rush into immediate surgery or radiation, even though it won’t prolong their lives. Tempering the government’s idea of nixing PSA screening ignores the well-established fact that the early detection of high-grade  disease saves lives. Forgoing PSA screening altogether is simply “throwing the baby out with the bathwater.”

A perfect prostate cancer screening test would detect high-grade disease while overlooking all the harmless low-grade stuff. Unfortunately, the present system—that of evaluating any PSA abnormality with an immediate 12-core random needle biopsy—diagnoses high- and low-grade disease with equal frequency. And unfortunately, low-grade disease has been misnamed “cancer,” putting terrible fears into motion. Experience shows that anything called cancer, regardless if it is called “low-grade,” usually leads to immediate surgery or radiation even though it’s unnecessary.

Taking Precautions

Men who embark on a program of PSA screening, therefore, need to take several precautionary steps to prevent being sucked into this unfortunate, fear-filled scenario. First, a man should know that his PSA is only normal or abnormal as it relates to the size of his prostate gland. A high PSA can be from cancer, but it can also be due to a benignly enlarged prostate gland. As men age, their prostates commonly get bigger and produce more PSA. A rise in PSA from an enlarged prostate gland can be completely unrelated to cancer. So when the doctor tells you, “Your PSA is high, I want to refer you to a urologist to consider doing a biopsy,” your cogent response should be, “Please refer me for a high-quality 3T multiparametric MRI scan or a high-resolution color Doppler ultrasound scan to measure the size of my prostate gland.”

The scan will report the prostate size in cubic centimeters or “cc.”  The PSA level can then be interpreted as “normal” if it is about one-tenth of the prostate size. For example, a normal PSA for a 50cc-sized prostate gland would be 5. A normal PSA for a 70cc prostate is 7. The PSA is abnormally high, using the example of a man with a 50cc prostate, when it is 50% above the expected normal value of 5, in other words, above 7.5. (50% of 5 = 2.5.  The 2.5 figure is added to the normal value of 5 to generate the PSA value for the upper limit of normal for that sized prostate gland which in this case is 7.5).

Of course, additional factors besides prostate size may need to be considered when interpreting PSA. Prostate infections, lab errors and recent sexual activity can all cause temporary increases in the PSA level. The first logical step, even before doing a prostate scan, is to simply wait and recheck the PSA in a week. Temporary and unexplained elevations of PSA occur all the time and they often revert back to baseline without any intervention at all.

There are additional advantages to doing prostate imaging with multiparametric MRI or color Doppler ultrasound rather than doing a random 12-core needle biopsy.

  1. When a spot that is suspicious for high-grade cancer is detected, a targeted biopsy can be performed. This means only one or two needle samples are obtained instead of doing a dozen. This reduces the discomfort and the risk of infection considerably.
  2. If a slightly suspicious lesion is detected two options can be considered: The suspicious lesion can be targeted with a needle biopsy, or, patients can consider simply monitoring the situation closely by repeating the scan in six months to see if the lesion is growing or changing.
  3. Men with low-grade lesions (and PSA levels that are normal using the PSA definition described above) can forgo biopsy altogether and simply undergo a repeat scan after one year.

Prostate Imaging

Prostate imaging is a fantastic development but the technology is new and not all imaging centers are able to achieve equally high-quality results. The PSA screening protocol advocated in this article, using state-of-the-art scans as a substitute for doing a 12-core random biopsy, relies on the following assumptions:

  1. The imaging is performed with state-of-the-art equipment.
  2. The scanning is performed by well-trained technicians.
  3. The images obtained from the scan are interpreted by experienced radiologists.
  4. The information provided by the scan report is acted upon by an expert in prostate cancer.

Incompetence in any one of these areas can make conclusions drawn from scan reports misleading and unreliable.

We are long overdue for a good alternative to random 12-core needle biopsies. Prostate imaging, assuming it is well-performed, properly interpreted and sensibly managed brings about this long-awaited deliverance. The next step will be developing more quality imaging centers and more willingness from doctors to learn about and adapt to this new technology.

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