TUESDAY, July 17 (HealthDay News) — Regular mammography
screening has limited — if any — impact on breast cancer deaths, a new
evaluation of Swedish women contends.
“Our analysis found no or limited influence of mammography screening on
breast cancer mortality,” said Dr. Philippe Autier, at the International
Prevention Research Institute in Lyon, France. The report is published
July 17 in the Journal of The National Cancer Institute.
Finding no or limited impact in Sweden, he said, suggests that the same
might be true in other countries, including the United States.
However, the report has some built-in limitations, said Dr. Michael
Vannier, a professor of radiology and medicine at the University of
Chicago Pritzker School of Medicine, who wrote one of two editorials that
accompany the study.
“Measuring the way they did,” Vannier said, “it was almost impossible
to find an impact [of screening] on an individual basis.” Rather, as
nationwide screening was rolled out in Sweden by counties, the study
looked at screening in different counties over different time periods.
In Swedish counties in which screening began in 1974 to 1978, for
instance, death rate trends during the next 18 years were similar to those
before screening started. In other counties, studied in other time periods
when screening started there, death rates sometimes increased and in other
counties decreased.
Death rates from breast cancer in Swedish women, overall, started to
decline in 1972, Autier found, before screening was introduced.
The overall net effect, however, was limited or no impact from
screening on the death rates.
Even so, Vannier said that the report should not be a reason for women
aged 40 and older to stop regular routine mammography screening. In the
second editorial, Nereo Segnan of ASO S Giovanni Battista University
Hospital in Turin, Italy, and his colleagues write 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 health
care.”
According to study author Autier, randomized trials conducted early on
found that screening did reduce the breast cancer death rates. His new
study, he said, along with others reinforce the idea that the trials were
biased.
“This is a study that is looking at the past,” Vannier countered.
Screening and treatment are better now, he said.
The study looks at the impact of screening on a population, not an
individual basis, Vannier said. “They basically followed the population,
counted the number of individuals who were invited to screening, [and]
counted the number who died,” he said. “Death records are notoriously
unreliable [as to cause of death],” he said.
Sweden now has a system “that is a kind of model for the world,”
Vannier said. Putting the nationwide screening into practice took a number
of years. “This is a test of it in the early days, and only has limited
follow up,” Vannier said. “The benefits of screening are cumulative.”
Autier said the findings should motivate health care providers to
present mammography in a different light. “Information to women on
mammography screening should better reflect uncertainty on the
effectiveness of that test, and underline the risk of overdiagnosis and
overtreatment,” Autier said.
Vannier said mammography screening is not perfect, of course. “The
alternative to not having a screening program is having the disease and
not knowing it,” he said.
More information
To learn more about mammograms visit the U.S. National Cancer Institute.
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