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Brendon Nafziger, DOTmed News Associate Editor | August 01, 2011
The Netherlands started a national program in 1989, but reached full coverage in 1997, when about 70-79 percent of women aged 50-69 were screened. From 1989 to 2006, breast cancer rates there fell 25 percent. In Belgium, the national program began in 2001; by 2005, only 59 percent of women aged 50-69 were screened or had a diagnostic mammogram in the previous two years. Yet death rates fell 20 percent in Belgium, and 25 percent in Flanders, in the same 17-year period.
Looking over the data, researchers said they didn't find any difference in access to treatment or disease risk among the different groups that would have masked the beneficial effects of screening. But they cautioned because it's a population-level study, there could be an unknown confounding factor, as yet undiscovered.
Radiologists respond
In a joint statement, the American College of Radiology and the Society of Breast Imaging said the study had several flaws that could have prevented it from picking up on the benefits of mammography.
For instance, the groups said the authors did not control for differences in the cancer incidence rates between the country pairs. Even though countries are neighbors, ACR and SBI said, they could have very different cancer trends. Sweden, for example, had a 10 percent greater breast cancer rate than Norway during the study period. "That would influence mortality rates over time —- as mortality rates are a function of incidence rates over time and their corresponding survival," the groups said.
Also the radiology societies said the mortality data from 1986-1996 are "contaminated" with deaths attributable to breast cancer that occurred before screening was introduced -- about half of those deaths.
"That leaves insufficient time to measure a population-wide effect," they said.
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