(HealthDay News) — Annual mammography does not reduce mortality from breast cancer among 40- to 59-year-old women, according to research published Feb. 11 in BMJ.
Anthony B. Miller, MD, from the University of Toronto, and colleagues conducted follow-up analyses of a randomized screening trial involving 89,835 women aged 40 to 59 years. The women were assigned to mammography (five annual mammography screens; 44,925 women) or control (no mammography; 44,910 women) from 1980 to 1985. Participants were followed for up to 25 years.
The researchers found that, during the screening period, 666 invasive breast cancers were diagnosed in the mammography arm and 524 were diagnosed in the control arm. And, 180 and 171 of these women, respectively, died of breast cancer during follow-up (hazard ratio [HR] for death from breast cancer diagnosed during the screening period associated with mammography, 1.05; 95% confidence interval [CI], 0.85 to 1.30).
During the entire study period, 3,250 women in the mammography arm and 3,133 in the control arm had a diagnosis of breast cancer, and 500 and 505, respectively, died of breast cancer. Cumulative mortality from breast cancer was similar between the two groups (HR, 0.99; 95% CI, 0.88 to 1.12). In the mammography arm, there was a residual excess of 106 cancers after 15 years of follow-up, due to over-diagnosis.
The researchers emphasized that the study results may not be generalizable to all countries, noting that early detection “could be of greater benefit in communities where most cancers that present clinically are larger and a higher proportion are node positive.”
“However, in technically advanced countries, our results support the views of some commentators that the rationale for screening by mammography should be urgently reassessed by policymakers,” they wrote. “Nevertheless, education, early diagnosis, and excellent clinical care should continue to be provided to women to ensure that as many breast tumors as possible are diagnosed at less than 2 cm.”
In an accompanying editorial, Mette Kalager, MD, PhD, of the University of Oslo in Norway, the Harvard School of Public Health in Boston, and Telemark Hospital in Skien, Norway, and colleagues supported the researchers’ conclusion that the notion of screening mammography requires another look.
“As time goes by we do indeed need more efficient mechanisms to reconsider priorities and recommendations for mammography screening and other medical interventions,” they wrote. “This is not an easy task, because governments, research funders, scientists, and medical practitioners may have vested interests in continuing activities that are well established.”
- Miller AB, Wall C, Baines CJ, et al. Twenty five year follow-up for breast cancer incidence and mortality of the Canadian National Breast Screening Study: randomised screening trial. BMJ. 2014;doi:10.1136/bmj.g366.
- Kalager M, Adami HO, Bretthauer M. Too much mammography. BMJ. 2014;doi:10.1136/bmj.g1403.