The screening mammo battle: No end in sight
The Sept. 23 NEJM included results of a Norwegian study in which Mette Kalager, MD, of Cancer Registry of Norway, Oslo, attributed a mere one-third of the 10 percent reduction in Norwegian breast cancer deaths to the country's screening mammography program.
The study adds to a massive pile of research.
“In the past 50 years, more than 600,000 women have participated in 10 randomized trials, each involving 10 years of follow-up,” writes H. Gilbert Welch, MD, MPH, of Dartmouth Institute for Health Policy and Clinical Practice in Lebanon. N.H., in an accompanying editorial comment.
Yet, the intense scrutiny goes on. Welch surmises that both the Norwegian study's finding of relative reduction in mortality due to screening as low as 2 percent and the 15 to 23 percent figure used by the U.S. Preventive Services Task Force may be correct.
Screening may have been more effective in the past than it is now, he argues. The observational Norwegian study applies to more recent data, whereas the Task Force data reflected earlier randomized trials.
Relatively recent data gathered over the last two decades may reflect earlier evaluation and better treatment. Specifically, when women with new breast lumps seek earlier evaluation, screening benefits fall. Improved treatment also reduces the benefit of screening.
According to Welch, “By highlighting that the mortality benefit is modest, Kalager et al help confirm that the decision about whether to undergo screening mammography is, in fact, a close call.”
Other experts disagree and argue that the new findings will confuse women and physicians. This "side," and it has morphed into a true battle, cites reams of additional data and a 30 percent drop in the breast cancer death rate since the 1990s.
Maybe it’s time for a truce. Kalager acknowledges the complex and systemic nature of the debate. “Most important, the apparent benefit conveyed by optimized patient care may be missed unless breast cancer screening is integrated into a well-functioning healthcare system that is available to the entire population.” Unfortunately, she seems to be describing another battlefield.