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.
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.
The teams reached somewhat different conclusions, but were closest to each other in estimating how much the adjuvant therapies tamoxifen and chemotherapy reduced mortality in patients (12 percent to 21 percent, with a median of 19 percent). The range for screening mammography, however, was 7 percent to 23 percent (with a median of 15 percent), reflecting the greater uncertainty associated with estimating the benefit of screening.
"While we didn't agree with each other as to the percentages of benefit, all seven groups concluded that the decline in the rate of death from breast cancer is a combination of screening and therapy and not restricted to one or the other," he says. "Screening would have no benefit if not followed by treatment, including surgery, and treatment has the potential to be more effective if cancer is detected at earlier stages by screening."
