As of Thursday, October 16, 2014
DEAR DOCTOR K: I’ve heard so many conflicting opinions about whether or not to get screened for prostate cancer. Are there official guidelines? What do they recommend?
DEAR READER: To say that prostate cancer screening has been controversial is an understatement. I spoke to my colleague Dr. Marc Garnick, clinical professor of medicine at Harvard Medical School, to hear his thoughts.
The two ways to screen for prostate cancer are the digital rectal exam (DRE) and the prostate-specific antigen (PSA) blood test. PSA levels rise when the prostate has turned cancerous, but they also rise when the prostate is just irritated or damaged. Together, PSA testing and DRE may nearly double the detection rate for early-stage prostate cancer.
But there’s a catch. Because other prostate conditions besides cancer can raise the blood levels of PSA, an elevated PSA does not always mean a man has cancer. We call a high blood level of PSA in a man without prostate cancer a “false positive” result.
False positive results can cause needless worry. And they may lead to invasive procedures, such as biopsies, to determine if cancer is present. No test is perfect: There is always the chance of a false positive result. But it happens pretty often with the PSA test.
The bigger problem, however, is this: As strange as this may sound, not all cancers are bad for your health. Some prostate cancers are so small and slow-growing that they will never spread and cause problems: You’ll die of something else. You’ll die with prostate cancer, but not from prostate cancer.
Of course, some prostate cancers are aggressive and very definitely a threat to a man’s health. So what we really want to have is a screening test that detects these aggressive prostate cancers.
Unfortunately, the PSA test cannot distinguish well between aggressive and slow-growing tumors. The former may require immediate treatment, while the latter may need no active treatment at all.
A final weakness of the PSA test is that it does not detect all cancers. In other words, just as the test can be falsely positive, it can also be falsely negative: It comes back normal (“negative”), but you really do have prostate cancer. In such cases, a PSA test offers a false sense of security.
In 2013, the American Urological Association came out with new guidelines that are more or less in line with those of other groups. These guidelines advise against routine screening for men at average risk who are under age 55 or over age 70. For men aged 55 to 69, the guidelines advise that doctor and patient make the decision together, based on a man’s individual risks, preferences and values. (I’ve put a more detailed summary of the guidelines on my website, AskDoctorK.com.)
I order PSA tests in many men aged 55 to 70. But like many doctors, what I’m waiting for is a better test that detects aggressive prostate cancers accurately and ignores the slow-growing ones.
Dr. Komaroff is a physician and professor at Harvard Medical School. To send questions, go to AskDoctorK.com, or write: Ask Doctor K, 10 Shattuck St., Second Floor, Boston, MA 02115.