Doc: How can screening be harmful?
Dear Dr. Roach: Every article I have read about prostate screening fails to define “screening.” I had thought of screening as the PSA blood test and/or the digital exam. But since you and everyone else describe the screening itself as possibly harmful, it must consist of more than I had in mind. I would appreciate an explanation.
Dear R..G.: A screening test is one that is done to diagnose a condition in someone who has no symptoms of the condition. Strictly speaking, much of gathering your medical history involves asking screening questions (such as, “Do you have any shortness of breath?”); the physical exam often qualifies as a screening test; and there are many blood and radiology tests that are used to screen.
A good screening test is safe and inexpensive. A condition appropriate for screening is one that is common enough to make screening worthwhile, serious enough to matter and has better outcomes if treated early, compared with treating after symptoms develop.
For prostate cancer in particular, the screening tests themselves aren’t the problem: A tube of blood or a physical exam may be unpleasant, but not really harmful. The harm can come when the screening test turns positive. An abnormal PSA test often leads to a biopsy, which itself can occasionally cause harm. Then again, the real harm comes after the biopsy, when cancer can be diagnosed. Some cancers are very indolent, meaning they grow slowly and are unlikely to cause problems in the foreseeable future. Some men wish to remove any type of cancer, no matter how small the risk of growth, and instead will choose to undergo treatment rather than take a wait-and-see approach. It is these treatments — usually surgery or radiation — that have the potential for harm, as many men develop side effects that impair their quality of life, especially sexual side effects and incontinence of urine.
There are two ways to avoid possible harm from a screening test: Don’t do one (which some groups recommend when it comes to prostate cancer screening), or do the test only if you are prepared to be rational about the findings. That means you can get the benefit of possibly finding and treating an aggressive cancer early, but can avoid unnecessary treatment for a low-risk or very-low-risk tumor. It isn’t always easy to be rational about these choices, so it’s important to know ahead of time what the possibilities are.
Dear Dr. Roach: Over two decades ago, my primary physician put me on plain niacin tablets each morning and each evening when he discovered that I had a cholesterol of 382. In the time since and after that doc retired, new docs have put me on better and better cholesterol medicine, the latest being 40-mg tabs of rosuvastatin (Crestor) every evening. The result has been excellent: My cholesterol reading was last at 170 and had been as low as 130. None of my docs nor I have noticed any bad reactions from the niacin. My docs, though they often wonder about it, assume it apparently has positive effects.
Dear G.R.: I wrote recently about the fact that niacin can raise blood sugar, but I’m afraid I didn’t get across my main point: We lower cholesterol not because we like seeing a good number, but because we want to lower the risk of heart disease. Unfortunately, the most recent studies show that although niacin makes the numbers better, it probably does not reduce the risk of heart disease more than taking rosuvastatin (or a similar statin drug) by itself. The niacin may not be causing you side effects, but I’m not at all sure that it’s really helping you.
Email questions to ToYourGoodHealth@med.cornell.edu.