Though most cases of prostate cancer have a good prognosis, the disease is the second leading cause of cancer deaths in American men, according to the Centers for Disease Control and Prevention (CDC). As with other cancers, early detection and treatment may be important for surviving prostate cancer, at least for advanced forms of the disease. Today, the most common screening test for prostate cancer is the prostate-specific antigen or PSA blood test, which measures the levels of the PSA enzyme in the blood.
Function of PSA
The prostate is a walnut-sized gland, situated between the bladder and penis, that’s part of the male reproductive system. Its main function is to produce fluid that partly makes up semen, which helps transport and protect sperm produced by the testicles. The prostatic fluid contains various substances that help sperm cells function and survive, one of which is PSA. This enzyme thins or loosens up semen, allowing sperm cells to swim freely while in the female body. Some of the PSA produced by prostate cells also makes its way into the blood. Both normal prostate cells and cancer cells make PSA. This suggests that elevated levels of the enzyme in the blood could signify prostate cancer, since prostate cancer is, after all, an out-of-control growth of abnormal prostate cells; more cells equal more PSA.
PSA Screening
In the United States, the PSA test was initially introduced in 1987 and quickly became a widespread early screening tool for prostate cancer, according to a 2014 report in the Journal of the American Medical Association (JAMA). Most healthy men have PSA levels in the blood less than 4 nanograms per milliliter (ng/mL), so the chance of having prostate cancer (or other prostate issues) increases as PSA concentrations increase. In the past, doctors would use a “cutoff” level of 4 ng/mL during PSA screening tests, though some doctors would use a cutoff point of 2.5 ng/mL — if their patient had higher levels, they would recommend a prostate biopsy to look for prostate cancer. However, men with low PSA levels can have prostate cancer, and men with high PSA levels may not have prostate cancer, because numerous factors can affect PSA production. Specifically, factors that can increase PSA levels include:
Prostatitis, or prostate inflammationEnlarged prostateCertain medicationsOlder age
Additionally, obesity and certain medications can cause low PSA levels.
PSA Recommendations
In recent years, the routine use of PSA screening tests in men without symptoms or in those who are high risk (with a family history of the disease, for example) has become controversial. The tests accurately detect prostate cancer 25 percent of the time, according to the U.S. Preventive Services Task Force (UPSTF), an independent panel of experts that makes evidence-based recommendations about clinical preventive services. Still, it may be difficult to tell if tumors found from follow-up biopsies will remain relatively benign or become lethal, potentially resulting in overtreatment and its associated harms. In 2012, the UPSTF found little benefit and significant harm to routine PSA-based screening for prostate cancer, and subsequently recommended against these tests. According to the UPSTF, studies suggest that PSA screening and early cancer treatment only prevents 0 to 1 death per 1,000 men screened. However, nearly 90 percent of men with PSA-detected prostate cancer in the U.S. undergo early, potentially harmful treatment, the UPSTF states. For instance, up to 5 in 1,000 men will die within one month of prostate cancer surgery. Additionally, radiotherapy and surgery can result in long-term health issues, including urinary incontinence and erectile dysfunction in up to 300 of every 1,000 men treated. Other advisory committees and authors of review articles, including the 2014 JAMA report, also recommend against routine PSA screening. No agency has recommended the use of the tests without considerable discussions of its pros and cons, according to the National Cancer Institute.
