Rather, women in their forties and fifties need not worry about annual mammography, investigators from the University of Toronto say. Some 22 percent of breast cancer diagnoses from screenings turn out to be false alarms.
Investigator Mette Kalager and his colleagues followed more than 89,000 middle-aged women over a quarter-century, including many who did not undergo annual breast cancer screenings. Past research had shown that women diagnosed from screenings with small (non-palpable) breast cancer lived longer than those with palpable breast cancer. But medical investigators questioned whether increased screenings helped save lives or was merely an illusion conjured from misperceived data.
In the study, women who received mammography underwent a total of five annual screenings over five years, while others in the control group did not receive screenings. However, most of the women also received annual physical breast exams, with the exception of the forty-something women not receiving annual breast exams. Those women were given only one examination as part of the study, maintaining their usual regimen of care.
The score? More than 3,200 of the women in the mammography group were diagnosed with breast cancer, along with some 3,100 among those who received no screenings. In both groups, approximately 500 women had died by the end of the study.
"Thus, the cumulative mortality from breast cancer was similar between women in the mammography arm and in the control arm," Kalager said Tuesday in a statement.
Over the course of the past quarter-century, investigators looked at diagnoses at regular intervals. By the five-year mark, 142 breast cancers had been over-diagnosed among women receiving mammography screenings. By year 15, that number of over-diagnosed cancers remained at 106, implying a high degree of false-positives in the breast cancer screening game.
Kalager warned that the findings might not apply to the developing world but have meaning for technically advanced nations. “Our results support the views of some commentators that the rationale for screenings by mammography should be urgently reassessed by policymakers.”
Although women should continue to visit the doctor regularly and administer self-exams, annual mammography “does not result in a reduction in a breast cancer specific mortality for women ages 40-59 beyond that of physical examination alone or usual care in the community.”
Source: Annual screening does not cut breast cancer deaths, suggests Canadian study. BMJ. 2014.