PSA (Prostate Specific Angtigen)

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PSA (Prostate Specific Angtigen) – What it Means?

Prostate-specific antigen (PSA) is a substance made by cells in prostate gland (it is made by both normal cells and cancer cells). Although PSA is mostly found in semen, a small amount is also found in the blood. Most healthy men have levels under 4 nanograms per milliliter (ng/mL) of blood. The chance of having prostate cancer goes up as the PSA level goes up. When prostate cancer develops, the PSA level usually goes above 4. Still, a level below 4 does not mean that cancer isn’t present — about 15% of men with a PSA below 4 will have prostate cancer on biopsy. Men with a PSA level in the borderline range between 4 and 10 have about a 1 in 4 chance of having prostate cancer. If the PSA is more than 10, the chance of having prostate cancer is over 50%.

The PSA level can also be increased by a number of factors other than prostate cancer, such as:

  • An enlarged prostate, such as with benign prostatic hyperplasia (BPH), a non-cancerous enlargement of the prostate that many men get as they grow older.
  • Age: PSA levels will also normally go up slowly as you get older, even if you have no prostate abnormality.
  • Infection or inflammation of the prostate gland (prostatitis)
  • Ejaculation can cause the PSA to go up for a short time, and then go down again. This is why some doctors will suggest that men abstain from ejaculation for 3 days before testing.
  • Riding a bicycle
  • Certain urologic procedures

Why it Matters

On one hand prostate cancer is very common and most men that have it are not affected by it. On the other hand it is the number two cancer killer of men in America. Determining the behavior of a prostate cancer is critical in making recommendations on what to do. The first step is to determine if your PSA abnormality is significant.

Absolute Value

When PSA was introduced a cut off of 4.0 was used to achieve what scientists and doctors felt to be an acceptable level of sensitivity (how many cancers the test recognizes) and specificity (how accurate it is if positive). We soon realized that although this was helpful it missed too many cancers in young men and resulted in too many biopsies and over diagnosis in older men.

Age Based PSA

We know that PSA rises as you age. By having a lower cut off in younger men and a higher cut off in older men we are able to catch cancers sooner in the younger population while eliminating a lot of unnecessary biopsies in the older population. There are several accepted reference ranges; one of the most common is this:

Abnormal Value

46-55      < 2.5
56-65      < 3.5
66–75     < 4.5
>75          < 6.5

Prostate Specific Antigen Test Glendale AZ
Prostate Specific Antigen Treatment Glendale AZ

PSA Free and Total

While PSA is a protein that is in our blood stream it is not all existing in the same form. Some is free floating and some is bound to other proteins. It was found that benign disease (not cancerous) tends to have higher levels of free PSA (>25%) and patients with prostate cancer tend to have lower free PSA (<15%).

These numbers can help stratify the risk in some men. For example if a patient has a PSA of 8.0 and had a negative biopsy, knowing that he has a PSA free >25% gives us more assurance that he doesn’t have prostate cancer.

PSA Density

We know that PSA rises as the prostate gets larger. Men with large prostate glands tend to have higher PSA’s. A normal size prostate is about 25 grams. We consider anything larger than 40 grams as enlarged. A normal PSA density is 0.1 PSA for every gram of prostate. This makes sense as a large, 40 gram prostate would have a corresponding upper limit PSA of 4.0. This helps us in men who have had a negative biopsy and have enlarged prostates. We are less likely to worry about someone with a PSA of 6.0 if there prostate is > 60 grams. Conversely, we are more worried if the PSA is elevated in a smaller prostate (PSA of 4.2 in a 17 gram prostate).

PSA Velocity

One of the most accurate ways of diagnosing prostate cancer is looking at the rate of rise of PSA. A PSA should never go up more than 0.7 points per year. For example, it would probably be better to have a PSA count over 3 checks go from 5.0 to 5.1 to 5.2 then it would be to have your PSA count go from 1.0 to 2.0 to 4.0.

Summary

Prostate Specific Antigen is only a tool. It is far from perfect but it is useful when the patient and their physician work together to make shared decisions. Since the onset of PSA screening the death rate from prostate cancer has been cut in half. Prostate Cancer is still the number two cancer killer of men in the United States. There is still much to be learned. Getting as much information as possible and making shared decisions with your doctor will help you understand the risks and benefits of checking your PSA and what to do with the information.

(From an article I wrote originally for about.com)

What’s new with PSA testing?

The last several years have brought us many new tools to help understand what your PSA means. There are several blood tests (4K etc) and urine tests (ExoDx etc) that help us stratify patients with elevated PSA to determine their risk of having high grade prostate cancer.

MRI Fusion Biopsy

One of the most effective tools we have currently is the MRI. In about 2015 it became evident that newer MRI techniques using multi-parametric MRI (mpMRI) could visualize more aggressive forms of prostate cancer while not showing the less aggressive forms. The Prostate Imaging Reporting and Data Sytem (piRADS) is used to assess how suspicious an area is in your prostate. The MRI areas are given a piRADS score of 1-5. We typically recommend biopsy on areas that score piRADS 3-5. The higher the piRADS score the greater likelihood of having a clinically significant or aggressive cancer.

The real breakthrough came soon after when a technique called fusion biopsy was described. The MRI is fused to ultrasound imaging real time so that we can target these suspicious lesions. In several large studies the use of MRI and fusion biopsies decreased the number of patients that needed biopsy and actually increase the accuracy of biopsy over our standard ultrasound guided random biopsy technique.I personally favor the UroNav system which I helped introduce to Arizona in 2017. I use this and with the help of a board certified anesthesiologist try to make it as painless as possible.