Blood Test Screening for Prostate Cancer

You might be aware that prostate cancer is the cancer of the prostate. The prostate is a small gland resembling walnuts that produces seminal fluid. You don't get screening when you already have the symptoms. The screening is like a test to check if you have cancer before the symptoms appear. It is like staying a step ahead in diagnosing or treating cancer. There are many ways to screen for prostate cancer. One such way is a blood test. These tests are only indicative. If your blood test reveals something is off, you might have to opt for other tests like a biopsy to get a definitive answer.

Also Read: Prostate Cancer Awareness

PSA and blood tests

The blood tests rely on the PSA level in the body to suggest prostate cancer. PSA or Prostate-specific antigen is a type of protein. Both healthy and cancer cells in the prostate are responsible for producing this protein. Usually, semen has PSA, but blood also contains a small amount of PSA. The unit to measure PSA is nanogram per millilitre (ng/mL). The level of PSA may change in the case of prostate cancer. For example, an increase in PSA levels indicates prostate cancer. But there is no surety that the rise in PSA is a sign of prostate cancer.

Most doctors consider the level of PSA as 4 ng/mL or higher while choosing the other tests. While others may believe the PSA level of 2.5 or 3 may hint at prostate cancer. The level of PSA in most men is under 4 ng/mL of blood. Very often, this level goes above 4 when prostate cancer affects any man. However, some men with PSA levels under 4 ng/mL might have prostate cancer. It occurs in about 15 per cent of men.

If the PSA level is between 4 and 10, the chances of prostate cancer are around 25 per cent. While a PSA level above 10 means the chances of having cancer are more than 50 per cent. High PSA levels imply that you may undergo other tests to check for prostate cancer.

What are the factors affecting PSA levels?

Prostate cancer is not the only reason for an increase in PSA levels. Other factors can also affect the PSA levels, these are:

Enlarged prostate gland: Any benign growth or conditions like benign prostatic hyperplasia can cause PSA levels to increase. It may occur in older men.

Your age: PSA levels usually rise slowly with age, even if the prostate is normal.

Prostatitis: This is an infection or inflammation of the prostate that can increase PSA levels.

Ejaculation: This can cause a temporary increase in PSA levels. For this reason, some doctors suggest that men refrain from ejaculation 1-2 days before the test.

Biking: Some studies suggest that biking can increase PSA levels in the short term (probably because the seat puts pressure on the prostate), but all studies have found this.

Specific urological procedures: Some procedures performed in the clinic that affect the prostate, etc. Prostate biopsy or cystoscopy may increase PSA levels for a short time. Some studies suggest that rectal examination (DRE) may slightly increase PSA levels, but other studies have not found this. However, if you perform both the PSA test and the DRE during your visit, some doctors recommend that you take a blood sample for the PSA before the DRE, just in case.

Certain medications: Taking male hormones such as testosterone (or other medications that increase testosterone levels) can increase PSA levels. Some things can lower PSA levels (even if a man has prostate cancer):

• 5-?-reductase inhibitor: BPH or urine, such as finasteride (Proscar or Propecia) or dutasteride (Avodart) Certain medications used to treat problems with PSA levels can be reduced.
• Herbal Blends: Some blends sold as dietary supplements can hide high PSA levels. For this reason, it is important to let your doctor know if you are taking dietary supplements, even if they are not strictly aimed at prostate health.
• Other Specific Drugs: In some studies, long-term use of certain drugs such as aspirin, statins (cholesterol-lowering drugs), and thiazide diuretics (such as hydrochlorothiazide) may reduce PSA levels.

Also Read: What are the causes of prostate cancer?

Special PSA test

The PSA level of a screening test is sometimes referred to as total PSA because it contains different forms of PSA (discussed below). If you decide to have a PSA screening test and the results are not normal, some doctors may consider using different types of PSA tests to determine if you may need a prostate biopsy.

Percent-free PSA: PSA occurs in two major forms in the blood. One form binds to blood proteins and the other form circulates freely (unbound). Percent Free PSA (% fPSA) is the ratio of the amount of PSA that is freely circulating compared to the total level of PSA. Free PSA levels are lower in men with prostate cancer than in men without prostate cancer. If the PSA test result is borderline (4-10), the percentage of free PSA can be used to determine if a prostate biopsy should be done. A low percentage of free PSA means that you are more likely to develop prostate cancer and you probably need to have a biopsy.

Many doctors recommend prostate biopsy for men with a free PSA rate of 10% or less and advise men to consider a biopsy if it is between 10% and 25%. Using these cutoffs detects most cancers and helps some men avoid unnecessary biopsies. This test is widely used, but not all doctors agree that 25% is the best cutoff point to decide on a biopsy, and the cutoff may change depending on the overall PSA level.

Complexed PSA: This test directly measures the amount of PSA that is attached to other proteins (the portion of PSA that is not free). This test could be done instead of checking the total and free PSA, and it could give the same amount of information, but it is not widely used.

Tests that combine different types of PSA: Some newer tests combine the results of different types of PSA to get an overall score that reflects the chance a man has prostate cancer (particularly cancer that might need treatment).

These tests include:

• Prostate Health Index (PHI), combines the results of total PSA, free PSA, and pro-PSA
• The 4Kscore test, which combines the results of total PSA, free PSA, intact PSA, and human kallikrein 2 (hK2), along with some other factors

PSA velocity: PSA speed is not an individual test. This is a measure of how fast PSA increases over time. PSA levels usually increase slowly with age. Some studies have shown that these levels rise faster when men have cancer, but studies have shown that it is more reliable than the PSA level itself.

PSA Density: PSA levels are higher in men with large prostates. Doctors use transrectal ultrasound to measure the volume (size) of the prostate (see Prostate Cancer Diagnosis and Staging Tests) and divide the PSA level by the prostate volume. The higher the PSA density, the higher the likelihood of cancer. PSA density is less useful than the percent-free PSA test.

Age-specific PSA range: PSA levels are usually higher in older men than in younger men, even in the absence of cancer. The results of borderline PSA may be of concern to 50-year-old men, but not for 80-year-old men. For this reason, some doctors suggest comparing PSA results with those of other men of the same age. But doctors rarely use this test.

If your screening levels are not okay

In this case, your doctor might suggest other tests to look for prostate cancer. You might undergo tests like imaging tests or rectal examinations. Further testing can only reveal anything further. So, you should talk to your doctor and follow the instructions to carry out the tests.

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Reference:

1. Ilic D, Djulbegovic M, Jung JH, Hwang EC, Zhou Q, Cleves A, Agoritsas T, Dahm P. Prostate cancer screening with prostate-specific antigen (PSA) test: a systematic review and meta-analysis. BMJ. 2018 Sep 5;362:k3519. doi: 10.1136/bmj.k3519. PMID: 30185521; PMCID: PMC6283370.
2. Catalona WJ. Prostate Cancer Screening. Med Clin North Am. 2018 Mar;102(2):199-214. doi: 10.1016/j.mcna.2017.11.001. PMID: 29406053; PMCID: PMC5935113.