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Finding More Cancer Isn't the Answer
The problem with over-diagnosis is that it leads to over-treatment. Unfortunately, at the time of diagnosis, we cannot tell who has non-progressive cancer. So we tend to treat everybody -- and that's the real problem. Treatment can only harm people whose cancer is non-progressive -- a disease that was never going to bother them.
All our cancer treatments have harms. Disfiguring surgery and the nausea, fatigue and hair loss associated with chemotherapy have real quality-of-life consequences for patients. And simply having the diagnosis of cancer can be terrifying.
Doctors and the public need to understand that finding more cancer is not the answer. You want to know whether a test saves lives or reduces the number of people with metastatic cancer. And you want to know about the downsides: how many people suffer needlessly in the process.
The best test needs to do three things. It needs to find the right cancers -- the ones that kill people. It should not find the wrong cancers -- the ones that never bother people. And it should not cause a lot of false alarms. In fact, the best test is almost certainly not the one that finds the most cancer. That one almost surely will lead to the most over-diagnosis and the most false alarms.
For breast cancer, MRI may (or may not) be the best test. We just don't know. The only way to know is to do a true experiment -- a randomized trial -- in which half the participants have MRI while half have mammograms, and determine how many die from breast cancer in each group. These experiments are a lot of work and they take a lot of time. But they are the only way out of what is beginning to appear to be a vicious cycle: more and more testing finding more and more cancer, with the assumption of benefit. Now is the time to study this breast cancer test the right way, before it is prematurely adopted. To encourage this, perhaps MRI should be covered only for participants in a randomized trial.
The time has come for a more balanced view of early detection. The prevailing view is that more diagnoses can only help. The reality is much more nuanced: Some people may be helped, while others will almost certainly be harmed. Early detection is a strategy that turns many more people into patients. Its effect on how many people die is relatively small, at best. People will die from cancer, whether or not they are tested.
So while it's tempting to think that had Elizabeth Edwards had mammograms before she felt her lump in 2004, she would not have metastatic cancer now, that's wishful thinking. Given what we know from the randomized trials of mammography, it is likely that she would be in the same situation now even if she had had regular mammography. Unfortunately, people who do everything right -- that is, get routinely screened -- still get bad cancer. Just ask Tony Snow, who was reportedly screened several times a year. ·
H. Gilbert Welch, Lisa Schwartz and Steven Woloshin are physician researchers at the VA Outcomes Group and faculty members at Dartmouth Medical School. Welch is the author of "Should I Be Tested for Cancer? Maybe Not and Here's Why." The views expressed here are their own. Comments:firstname.lastname@example.org.