Participation in mammography screening substantially reduced rates of advanced and fatal breast cancers, according to results of a retrospective study conducted in Sweden.
Researchers observed the benefits of screening regardless of evolution in treatment regimens over time.
“Some may believe that recent improvements in breast cancer treatment make early detection less important,” László Tabár, MD, professor in the department of mammography at Falun Central Hospital in Sweden, said in a press release. “Our study shows that nothing can replace finding breast cancer early.”
A previous study of a defined population in one Swedish county evaluated the effect of mammography screening on breast cancer mortality by looking at incidence of the disease becoming fatal within 10 to 20 years after diagnosis. That analysis considered the determinants of death due to breast cancer, exposure to mammography screening and breast cancer treatment as part of the same time period.
Overall, researchers identified a 60% reduction in incidence of fatal breast cancer within 10 years of diagnosis among women who underwent screening compared with those who did not receive screening.
Tabár and colleagues expanded that study to include 549,091 women, which covered about 30% of the Swedish screening-eligible population.
Researchers calculated the incidence rates of 2,473 breast cancers that were fatal within 10 years after diagnosis, as well as incidence rates of 9,737 advanced breast cancers.
They gathered data from national Swedish registries on each breast cancer diagnosis and the date of death for each case, and collected tumor characteristics from regional cancer centers. Average time of observation was 13 years for occurrence of breast cancer that was fatal within 10 years of diagnosis and 22 years for incidence of advanced disease.
Results showed women who participated in mammography screening had a 41% reduction in risk for dying of breast cancer within 10 years (RR = 0.59; 95% CI, 0.51-0.68) and a 25% reduction in the rate of advanced breast cancers (RR = 0.75; 95% CI, 0.66-0.84).
A lack of data on the extent of mammography screening being offered by private facilities — which is restricted mostly to the Stockholm region — served as a limitation to the study.
“This study shows that participation in breast cancer screening substantially reduces the risk [for] a fatal breast cancer,” Stephen W. Duffy, MSc, professor of cancer screening at Queen Mary University of London, said in a press release. “Because the comparison of participating with nonparticipating persons was contemporaneous — with mammography screening and breast cancer treatment belonging to the same time period — it is not affected by potential changes in treatment of breast cancer over time.” – by John DeRosier
Disclosures: Tabár reports personal fees, travel expenses and honoraria from General Electric Healthcare, personal fees from Mammography Education Inc. in his capacity as president of the company, and personal fees from Three Palm Software. Please see the study for all other authors’ relevant financial disclosures.