Today’s issue of the highly respected Cochrane Library collection of systematic evidence reviews estimates that women who are screened for breast cancer are 15 percent less likely to die from the disease than those who are not screened. But there is a cost, because those who are screened are 30 percent more likely to be diagnosed and treated for a cancer that never would have threatened their health.
Put another way, for every 2,000 women who are screened for 10 years, one will have her life prolonged as a result. But 10 will become cancer patients and be treated unnecessarily. Another 200 will be told the X-ray has found something suspicious, only to undergo untold anxiety and further testing before finding out it was a false reading.
The dilemma here is not whether to have a mammogram, but how to improve the diagnostic process and how to proceed once a diagnosis is made.
For those questions and so many others, evidence can help inform a decision, but the final answer – for patients, for doctors and for insurers — still depends on a good guess.