The American College of Radiology (ACR) and the Society of Breast Imaging (SBI) have issued a statement claiming that the results of a British study have little bearing on, or resemblance to, screening in the U.S.
Published in the July 28 issue of the British Medical Journal, the study says there exists no evidence that mammography screening served a direct role in reducing breast cancer deaths in European countries where screening has been implemented. The authors compared breast cancer mortality trends in three pairs of adjacent countries. Each comparison included a country that introduced mammography screening some years earlier than the other.
Comparing breast cancer death rates from 1989 through 2006, the authors observed similar trends in breast cancer death reduction in each pair. They claim mortality trends are more likely influenced by therapy improvements than mammography screening.
“Improvements in therapy have likely played a role in the decrease in breast cancer deaths, but therapy cannot cure advanced cancers,” counter the ACR and the SBI. “Early detection via mammography is clearly the major reason for the decrease in deaths in the U.S.”
Moreover, the societies cite several reasons why the analysis published in the British Medical Journal fails to demonstrate more dramatic differences in breast cancer death rate declines based on timing of mammography introduction in Europe. Notably, they claim, the mortality data are contaminated with deaths attributable to breast cancer diagnoses that occurred before screening was introduced. They also point out that just because two nations share similar geography, does not mean their breast cancer mortality trends are easily compared, and that the authors did not adjust for incidence rate differences between comparison nations.
The study also does not account for the fact that not all women who develop breast cancer have been invited to screening, and that not all those invited for screening are subsequently screened. Finally, the societies assert, the study did not demonstrate how effectively mammography is functioning in comparison countries. The effectiveness of mammography on a population-wide basis is influenced by the attendance rate and the accuracy of the screening, they conclude.
To read the abstract, click here: http://www.bmj.com/content/343/bmj.d4411