To Screen-or Not?
Questions to put to your physician before having a test
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.
What you really want to know, though, is whether a test saves lives by catching and permitting the treatment of cancers that would be deadly when detected months or years later. Take a tumor of the neuroendocrine system called neuroblastoma. It is the most common malignant tumor in children, so any and all efforts to find it early would seem to be worthwhile. A screening test was developed that examined infants' urine for certain chemicals produced by this cancer. The test was used in Japan for 20 years starting in the mid-1980s, but it was abandoned after researchers surveyed the accumulated data. Many more infants had been diagnosed with early-stage disease-but those same cases almost always had the biological hallmarks of the kind of neuroblastoma that has a high survival rate after it's detected because of symptoms. Many of the infants had had tumors that never would have caused a problem later. That means they were unnecessarily treated with surgery, radiation, or chemotherapy, all of which carry the risk of harm or even death. There was no drop in the incidence of the most dangerous cases. And using the test had no effect on mortality.
For some tests, no one knows whether having them will reduce deaths from the disease. The U.S. Preventive Services Task Force, an independent advisory panel that issues recommendations on preventive care, puts screening for lung, prostate, oral, and skin cancer in this category (box). For example, the task force says the PSA test for prostate cancer can definitely find early cancers, but whether that actually saves lives is unclear.
"Some people will say, gee, if you don't know the answers, maybe I shouldn't get [the test], while others will think they still may want it," says Russell Harris, a member of the task force and professor of medicine at the University of North Carolina. Laurie Fenton, president of the Lung Cancer Alliance, an advocacy group, is in the latter camp. The results of randomized trials of CT screening for people at high risk for lung cancer aren't due out for a few years, but she says people have the right to get the test if they understand the possible harm as well as the potential benefits. A possible factor: Your insurance may not cover the cost of tests that aren't recommended by government groups or the American Cancer Society.
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