Annual Mammography from Age 45 Onward Verified to Reduce Death From Breast Cancer
Dec. 17, 1999 (Atlanta) -- Annual breast cancer screening beginning at age 45 can dramatically curtail deaths due to breast cancer, according to an abstract presented at the 22nd Annual San Antonio Breast Cancer Symposium. The finding upholds the current screening recommendations of the National Cancer Institute. Additionally, screening twice-yearly from age 40 onward may yield an even greater reduction in such deaths.
In the U.S., breast cancer ranks as the most frequently diagnosed non-skin cancer among women, and associated risk rises as women age. Currently, the National Cancer Institute recommends that women age 40 and up receive mammograms every one to two years. Although many women also perform breast self-exams, this is not considered a substitute for clinical breast exams or mammography.
"We were surprised to see how effective mammography is at reducing breast cancer death if used frequently enough," lead author James Michaelson, PhD, tells WebMD. "[And,] we were surprised to see how much life is lost if mammography is not used frequently enough. ... The most important, immediate finding is that women should attend [breast cancer] screening promptly at 12-month intervals. That can lead to a great reduction in breast cancer death." Michaelson is an assistant professor at Harvard Medical School and is on staff at Massachusetts General Hospital in Boston.
In this study, a computer simulation model was developed based on estimates of the size of the smallest breast cancer tumors detectable on mammography and palpation, rates of growth, and rates of spread. Using a database, the model forecasted the number of deaths prevented due to breast cancer screening.
The findings agree with the 30% reduction in breast cancer deaths found in studies. The investigators found a 45% lifetime reduction in breast cancer death by annual screening from age 45 onward and a 60% lifetime reduction in breast cancer death by twice-yearly screening from age 40 onward. "The risk of death from breast cancer increases much more than linearly with time at 12-month intervals," says Michaelson. "It's based upon the underlying mathematical model of breast cancer growth and spread. We have learned that the probability of spread from the initial site occurs as a function of the number of cells in the tumor. As the tumor gets larger, the probability of potentially lethal spread increases."
Cost was determined most likely not to be a barrier to screening more often, according to cost-benefit analyses.
Future studies should further investigate whether twice-yearly screening is more beneficial than annual screening, says Michaelson.