A breast cancer screening program in Norway—which made mammographic screening available to women between the ages of 50 and 69—led to a smaller decrease in deaths by breast cancer than anticipated, according to a study led by Harvard School of Public Health (HSPH) researchers in the latest New England Journal of Medicine.
"The observed reduction in death from breast cancer after introduction of the mammography screening program was far less than we expected," said lead author Mette Kalager, a visiting scientist at HSPH and a surgeon at Oslo University Hospital in Norway. "The results showed that other factors—such as enhanced breast cancer awareness and improved treatment—actually had a greater effect on reducing mortality from breast cancer."
In Norway, each county is required to establish multidisciplinary breast cancer management teams—made up of specialized radiologists, radiologic technologists, pathologists, surgeons, oncologists and nurses—that women enroll in before entering the national screening program.
Among women older than 70 years—who were treated by multidisciplinary teams alone and not invited to undergo mammography screening—the study found an 8% reduction in death from breast cancer. Among women ages 50 to 69 who did undergo mammography screening, a 10% decrease in breast cancer deaths was reported.
"This can be explained by treatment of multidisciplinary teams...that manage the care of the patients," the authors said. "The 10% reduction we found among women aged 50 to 69 years old being invited to mammography screening can be attributed to both the mammograms and management by multidisciplinary teams."
The authors analyzed data from 40,075 women diagnosed with breast cancer who participated in the Norwegian breast cancer screening program. With the program, which began in 1996, the researchers compared the rates of death from breast cancer among four groups of women.