US Pharm. 2019;44(8):13-14

Measures Prostate-Specific Antigen in Blood

PSA (prostate-specific antigen) is a protein produced by the male prostate and is typically found in semen. Under normal conditions, a very small amount of PSA is released into the bloodstream by the prostate. In cases of prostate abnormalities, such as enlargement, infection, or cancer, more PSA is released into the circulation. For this reason, doctors have used the PSA test to detect higher than normal levels of PSA in the blood as a screening tool for prostate cancer. An increase in PSA in the blood does not, by itself, give the doctor a definitive diagnosis of prostate cancer.

High PSA May Call for More Testing

All men are at risk for prostate cancer. Out of every 100 American men, about 10 will get prostate cancer during their lifetime, and two to three men will die from prostate cancer. Almost all prostate cancers occur in men older than age 55 years, and half of the men who die from prostate cancer are over age 80 years. African-American men and men with a family history of prostate cancer have the highest risk.

Testing for prostate cancer includes both a PSA blood test and a digital rectal exam (DRE). A DRE allows the doctor to manually inspect the prostate for size and condition. In up to one-half of patients with an enlarged prostate found on DRE, the PSA level is above normal.

Interpreting Results

A normal PSA level is usually less than 4 nanograms per milliliter (ng/mL). A PSA between 4 and 10 ng/mL signals a 25% chance of prostate cancer, and a PSA above 10 ng/mL signals an even higher chance of prostate cancer. An elevated PSA level can also mean a noncancerous condition is present, such as an enlarged prostate gland (benign prostatic hypertrophy, or BPH), an inflamed prostate gland (prostatitis), or an infection.

If the PSA level is elevated and other findings are present, such as symptoms of urinary tract problems, blood in the urine, or a lump found during the DRE, the doctor may order further testing or a biopsy. During the biopsy, a sample of prostate gland tissue is taken through a tiny needle guided by ultrasound. The cells are examined by the pathologist to look for cancer. The results of the PSA and biopsy together are used to “score” the cancer, which helps the doctor determine the best treatment in each case. The PSA test is used to assess the efficacy of prostate cancer treatment. 

Changes to PSA Screening Recommendations

In many cases, men with increased PSA levels do not have cancer, and these men suffer a great deal of anxiety and financial cost as a result of unnecessary biopsies. Additionally, the biopsy itself is associated with a small risk of bleeding and infection. Also, low PSA levels do not necessarily indicate the absence of cancer.

In May 2018, the U.S. Preventive Services Task Force (USPSTF) updated its recommendation for PSA testing to screen for prostate cancer. Both the USPSTF and the American Academy of Family Physicians (AAFP) recommend that men between the ages of 55 and 69 years should make individual decisions about screening only after a discussion with their physician about the risks and benefits of screening. For men over age 70 years, PSA tests are not recommended, as the risk of the disease itself does not outweigh the risks of testing. There are no specific screening recommendations for men at higher risk of prostate cancer since there is insufficient evidence of the mortality benefits of screening. Many physicians will recommend regular testing in high-risk men only after discussing the associated risks and benefits. For those who decide to undergo screening, they should not be screened more frequently than every 2 years.

If you have questions about prostate cancer, risk factors, and screening recommendations, consult a trusted healthcare provider. Pharmacists can consult on the treatment of prostate cancer and the associated side effects.