Screening, adjuvant therapy combine for breast cancer mortality drop
Mammogram screening and adjuvant treatments have formed a two-pronged attack against US breast cancer mortality in the past 10 to 15 years, research published in the New England Journal of Medicine shows.
The study, conducted by the Cancer Intervention and Surveillance Modeling Network and sponsored by the National Cancer Institute, was designed to end controversy over whether screening programs or improved therapies have contributed most to the decrease in breast cancer deaths over recent years.
"Some people think the benefit of screening is huge, and others say that the reduction in death rates is due primarily to adjuvant therapy," lead author Donald Berry (University of Texas M D Anderson Cancer Center, Houston, USA) explained.
"No one has known for sure, and although we still don't know for sure, this is the best set of analyses that is possible given the available information."
The consortium of 43 investigators developed seven independent statistical models of breast cancer incidence and mortality using data regarding the use of screening and adjuvant treatments.
The seven teams differed in their conclusions, with a greater variability found in the absolute contribution of screening than for adjuvant treatments, reflecting the greater uncertainty associated with the former.
Adjuvant hormone treatment with chemotherapy was calculated to reduce patient mortality by between 12% and 21% (median 19%), while the reduction in mortality with screening mammography was thought to range from 7% to 23% (median 15%).
Overall, the combined efforts of screening mammography and adjuvant treatment were found to result in a 25% to 38% reduction in breast cancer deaths (median 30%).
"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," Berry emphasized.
"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."
The researchers hope that the models may "help determine what strategies for delivering medical care are best for patients," Berry added.
"And that is necessary, since our efforts, taken as a whole, haven't come close to eliminating breast cancer mortality."
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