Debating the benefits of mammography

A pair of this week’s top stories were studies demonstrating the benefits of mammography screening, but the authors of an editorial response to one of the studies seem to remain unimpressed.

The first study, published online in Cancer, looked at the incidence of late-stage breast cancers in the mammography era. Researchers from the University of Michigan Comprehensive Cancer Center in Ann Arbor, led by Mark Helvie, MD, aimed to see if the rates of early- and late-stage breast cancers had changed between the late 1970s, before mammography was popularized, and the late 2000s.

Based on breast cancer trends in the pre-mammography era, Helvie and colleagues calculated the expected annual percentage change in breast cancer incidence to be 1.3 percent per year. Using this figure, they determined that the incidence of late-stage breast cancer decreased by 37 percent compared with projections, while the incidence of early-stage cancer increased 48 percent, indicating a shift toward earlier detection since the advent of mammography.

The big headline study of the week, however, was the analysis of a Norwegian breast cancer screening program published online in BMJ. Harald Weedon-Fekjær, PhD, of the Department of Public Health at the Norwegian University of Science and Technology and the Oslo Center for Biostatistics and Epidemiology at the University of Oslo, and colleagues analyzed data from all Norwegian women aged 50 to 79 from 1986 to 2009, a total of more than 15 million person years of observation. Within the time period analyzed, a mammography screening program was gradually implemented that invited women aged 50 to 69 to undergo screening. Results showed that invitation to mammography screening was associated with a 28 percent reduction in the risk of death from breast cancer.

Weedon-Fekjær and colleagues also estimated that 368 women would need to be invited to screening to prevent one death from breast cancer, though they noted that improvements in treatment will actually increase the number of women needed to be invited to mammography to prevent one death.

Even with that caveat, the results of the study demonstrate the benefits of screening programs, but an accompanying editorial, co-authored by Joann G. ElmoreMD, of the University of Washington School of Medicine in Seattle, and Russell P. Harris, MD, of the University of North Carolina, Chapel Hill, was less enthusiastic.

“While the benefits are small, the harms of screening are real and include overdiagnosis, psychological stress and exorbitant healthcare costs,” wrote Elmore and Harris. They added that the Norwegian study merely confirmed that the benefits of screening mammography are “modest at best.”

We’d love to hear your take on the debate. Do you believe the benefits of mammography screening are substantial enough to balance out the harms noted by Elmore and Harris?

-Evan Godt
Editor – Health Imaging