Early detection through screening mammography and improved adjuvant treatment have contributed almost equally to the substantial decrease in breast cancer death rates over the past 10 to 15 years, researchers conclude in an unprecedented effort to parse out the factors that have led to the decline.

The study, published in the New England Journal of Medicine, was supported by the National Cancer Institute (NCI) and conducted by seven research groups, including The University of Texas M. D. Anderson Cancer Center.

Researchers sought to end the longstanding controversy of whether screening mammography, better treatment or a combination of the two is responsible for improved breast cancer survival. The seven teams consisting of 43 investigators designed their own statistical models to determine the contribution of each method. These independent models used the same sources of data, some of which had not been mined before, but their approaches and assumptions differed.