To Screen-or Not?
Questions to put to your physician before having a test
Once cancer cells break away from their original home and take up lodging elsewhere in the body, the disease can often be managed but is rarely curable-so finding cancers before they spread and symptoms appear makes sense. Hence the emphasis on timely screening to sniff out the very first signs of disease.
But any screening test is a balancing act. On one side is the obvious benefit of detecting cancer in time to save a life. On the other are less obvious risks. The medical community is in the midst of hotly debating which tests are right for which people-and whether ferreting out every last sign of cancer is always good. "The idea that a good screening test is the one that finds the most cancers is totally wrong," says H. Gilbert Welch, a physician researcher at the VA Outcomes Group in White River Junction, Vt., and author of Should I Be Tested for Cancer? Maybe Not and Here's Why. A good screening test, he says, is the one that saves the most lives and harms the fewest healthy people in the process.
Some tests, such as the Pap smear and those for colorectal cancer screening, have cleared that barrier with room to spare. Others, such as the PSA test for prostate cancer and CT screening for lung cancer, are murkier. Your comfort level depends on a talk with your doctor about whether a given test is right for you. Here are the key questions to ask when a test is proposed or when you want to discuss one you've heard about.
1. Why should I have this particular test?
With no symptoms as guidance, who should have a test comes down to the risk of getting the disease. Cancer is most often a disease of aging, so logically, screening for common cancers such as breast and prostate can wait until midlife. Other risks may depend on family history, specific genetic patterns (mutations in the BRCA genes dramatically increase the chance of getting breast cancer) or lifestyle factors such as smoking or exposure to carcinogens. If a doctor recommends a screening test, it's presumably because she thinks you are at some risk, however small.
Understanding the nature and degree of that risk is vital, says Dartmouth Medical School radiologist William Black, an expert in cancer screening. To bring it home, you can say you want to know your chances of getting the disease or dying from the cancer for which you would be screened within a year. How about 10 years? A lifetime? Out of 1,000 people with a risk profile like yours, how many will get the disease? And how does the physician know that? "If the doctor isn't well versed in that kind of information, a request should be made to be referred to one who is," says gastroenterologist Moshe Shike, who heads the screening recommendation committee at Memorial Sloan-Kettering Cancer Center in New York.
2. Will the test lower my chance of dying?
You'd think the answer would always be yes, but it's not that straightforward. The most reliable and definitive way to know is to take a number of healthy people in the population who might be candidates for screening and assign them randomly to a screened or an unscreened group, then follow them to see which group has fewer deaths. But such randomized controlled trials are expensive, and because most cancers develop slowly, conclusions can't be drawn for years. Meanwhile, people who might benefit are not getting the test. So other kinds of studies are often performed instead that use different effectiveness measures, such as whether use of the test raises the average survival rate over a certain period.
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