Prostate cancer screening
Some healthcare professionals recommend that men be offered screenings after age 50, and even earlier for men at higher risk because of their race or family history. The term “offered” is used because not all medical exper ts agree that screening saves lives, and research into understanding the benefits of screening is ongoing.
Whether to be screened for prostate cancer is a decision to be made by you and your doctor after discussing the facts. Screening has a benefit when it detects cancer early and makes treatments more effective. It can provide peace of mind. But screening is not without a downside. It can lead to treatments of cancers that would never have posed a danger to a man’s health, sometimes with long-term side effects.
Two common ways to check for prostate cancer are the digital rectal exam, or DRE, and prostate-specific antigen, or PSA, test. During a DRE, your doctor will insert a gloved, lubricated finger into the rectum and check for any physical abnormalities of the gland, which sits next to the rectum. The PSA test analyzes the level of a protein made by the prostate gland that is in the blood. In general, the higher the number, the more likely it is to signal cancer.
PSA numbers are expressed as nanograms of PSA per milliliter of blood, or ng/mL. Doctors hope for a number lower than 4. But don’t get overly fixated on that number; unlike common tests, such as cholesterol or blood pressure, there is no consensus on the threshold for normal. A PSA level can be elevated for other reasons. For example, PSA levels increase when a man has an enlarged prostate, even though there is no evidence that BPH causes prostate cancer; in general, PSA levels slowly increase with age. And a number below 4 doesn’t mean you’re in the clear. In one study, for example, 15 percent of men with a PSA of 4 or below actually had cancer. Drugs to treat BPH can also affect PSA test results by lowering PSA levels.
No cancer screening is perfect, and the PSA test has attracted its share of controversy. In a small number of cases, the PSA can miss cancers, leaving men to falsely think they do not have cancer when they actually do. It can also lead to unnecessary tests in an effort to rule out cancer, causing additional anxiety and expense—and exposing men to possible side effects, such as bleeding and infection. And while it may detect cancers earlier, it may not lower the mortality rate. In the Prostate, Lung, Colorectal, and Ovarian (PLCO) trial, prostate cancer deaths were no different in the screened group (50 deaths out of 38,343) compared with the unscreened group (44 deaths out of 38,350) after seven years of follow-up. All of these are factors to consider before taking the test.
The U.S. Centers for Disease Control and Prevention (CDC) explains the numbers this way: If 100 men over the age of 50 take a PSA test, 85 will have a normal PSA level (though a few may have cancer that was missed by the test). Of the 15 who have a higher-than-expected level of PSA, 12 will be found on further testing to be free of cancer, while three will have prostate cancer. So out of ever y 100 PSA tests, three cancers are found that would likely have been missed without the test. And there’s no guarantee that those three cancers would be life-threatening.
If your PSA level arouses suspicion but you have no sign of cancer, your doctor may recommend waiting and repeating the PSA test and the DRE. If your PSA continues to rise or symptoms appear, you may undergo fur ther testing to determine whether the cause might be cancer or something benign. Ultimately, doctors cannot determine whether cancer is present until you have a biopsy. During a biopsy, doctors use a needle to remove a small amount of tissue from the prostate to view under a microscope.
In the future, scientists hope to improve the PSA test, and perhaps introduce other, more precise methods to screen for prostate cancer. One proposed variation for PSA is to follow the rate of change in the number—a figure that rises quickly over time may be a more worr ying signal. Another method of interpreting PSA might be to compare the PSA number to the size of the prostate. If a man has an enlarged prostate for benign reasons, a high PSA might not be concerning (though this idea is still unproven).
Researchers are also looking for ways that might detect prostate cancer through more precise methods. For example, doctors might one day be able to examine biomarkers, genetic changes in prostate cancer cells that appear in the urine. And new blood tests are being developed that look for other proteins, in addition to PSA, that might indicate the presence of cancer.