New Swedish Mammography Research Finds No Survival Benefit

Emma Hitt, PhD

July 17, 2012

July 17, 2012 — New research evaluating the timeline of mammography introduction and its effect on death from breast cancer in Sweden indicates no benefit of screening mammography on overall survival. The results are bound to stir up the ongoing debates about this issue.

The findings, from a study conducted by Philippe Autier, MD, from the International Prevention Research Institute in Lyon, France, and colleagues, were published online July 17 in the Journal of the National Cancer Institute.

However, 2 accompanying editorials question the methodology used in this study, and call for an end to the ongoing debate on this issue.

In addition, Robert Smith, PhD, senior director for cancer screening at the American Cancer Society, told Medscape Medical News that the overwhelming weight of the evidence, including randomized trials, has shown reductions in mortality with screening.

"Although there have been a number of recent publications questioning the value of mammography screening, these studies suffer from a lack of adequate data and unsophisticated methodology," Dr. Smith explained.

"The key clinical take-home message is that early detection combined with state-of-the-art treatment can significantly reduce the mortality rate from breast cancer," he said.

According to Dr. Smith, "both early detection and improvements in therapy contribute to improved prognosis and reductions in breast cancer deaths. Regular breast cancer screening is an important part of a woman's preventive healthcare plan."

Screening Had No Impact in Sweden

Dr. Autier and colleagues evaluated data from the Swedish Board of Health and Welfare from 1960 to 2009 in women who were 40 years and older. They found that from 1972 to 2009, breast cancer mortality rates decreased by just under 1% per year, declining from 68.4 to 42.8 per 100,000 population, which is similar to the rate in the prescreening period.

In 14 of 21 counties, breast cancer mortality rates declined continuously from 1960 to 2009; in 3 counties, rates dropped steeply after the introduction of screening; in 1 county, rates declined 5 years after the introduction of screening; in 1 county, rates declined 11 years after the introduction of screening; and in 2 counties, breast cancer mortality increased after the introduction of screening.

In counties in which screening was introduced from 1974 to 1978, mortality trends during the next 18 years were similar to prescreening levels; in counties in which screening was introduced from 1986 to 1987, mortality increased by approximately 12% (P = .007) after the introduction of screening, compared with previous trends.

In contrast, in counties in which screening was introduced in 1987/88 and in 1989/90, mortality declined by approximately 5% (P = .001) and 8% (P < .001), respectively, after the introduction.

"We expected that the gradual implementation of screening in different counties would be associated with a gradual reduction in mortality that would culminate in the reductions predicted by previous randomized trials and observational studies," Dr. Autier and colleagues note.

They add that "it seems paradoxical that the downward trends in breast cancer mortality in Sweden have evolved practically as if screening had never existed."

In an interview with Medscape Medical News, Dr. Autier said that these "results reinforce the growing body of data showing that randomized trials on mammography screening were biased and ended up with results that suggest that reductions in breast cancer mortality are associated with screening."

He added that mammography screening increases the diagnosis of indolent cancers that are not life-threatening (overdiagnosis). "One should think about alternatives to mammography screening and provide women with information more in line with questions about the effectiveness of that screening test."

Methods May Be Unreliable

However, one of the accompanying editorials questions the method used in this study. "The analysis of time trends of breast cancer mortality rates following the introduction of screening is definitely not the most reliable method to assess its effectiveness," write Nereo Segnan, MD, from the Battista University Hospital, in Turin, Italy, and colleagues.

They also point out that the conclusion of the study is "also partially unsupported by the data; 2 of the 4 groups of counties do show a mortality decrease."

They suggest that "it is time to move beyond an apparently never-ending debate about the extent to which screening for breast cancer in the 1970s to 1990s has reduced mortality from breast cancer — as if it was isolated from the rest of healthcare."

Screening Not Easily Linked to Mortality

In another accompanying editorial, Michael W. Vannier, MD, from the University of Chicago Medical Center in Illinois, questions the use of death as a metric for measuring the effectiveness of screening. "Even if screening were 100% successful, if diagnosis and treatment were delayed or ineffective, the number of deaths might not be affected," he points out.

"It is not simple to understand what benefits screening provides, and we should regard any generalizations with skepticism," Dr. Vannier added.

J Natl Cancer Inst. Published online July 17, 2012. Abstract, Segnan et al Editorial, Vannier Editorial

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