ACR and SBI Statement on BMJ Article Regarding Effect of Mammography on Breast Cancer
Death Rates
There is a large body of evidence that mammography screening saves lives. In the mid 1980’s there was
a dramatic increase in the number of American women screened. The sudden increase in breast cancer
incidence seen in national statistics was followed by an abrupt decrease in deaths that began five to
seven years later. This decrease in deaths in conjunction with the onset of screening confirms the
favorable results of randomized trials, case-control studies and large population-based evaluations of
mammography screening.
Yet, a report in the July 28 British Medical Journal claims there is no evidence that mammography
screening served a direct role in reducing breast cancer deaths in European countries where screening
has been implemented. The authors compared breast cancer mortality trends in three pairs of adjacent
countries (Sweden vs. Norway; Northern Ireland vs. Republic of Ireland; and Belgium vs. Netherlands).
Each comparison included a country that introduced mammography screening some years earlier than
the other. Comparing breast cancer death rates from 1989-2006, the authors observed similar trends in
breast cancer death reduction in each pair. They claim mortality trends are more likely influenced by
therapy improvements than mammography screening.
The conclusions of the BMJ study authors have little bearing on, or resemblance to, screening in the
United States. Improvements in therapy have, likely, played a role in the decrease in breast cancer
deaths, but therapy cannot cure advanced cancers. Early detection via mammography is clearly the major
reason for the decrease in deaths in the U.S. This is the life-saving effect that the authors of the BMJ
study expected to see in Europe (as was seen in cervical cancer screening).
While one may intuitively expect to see more dramatic differences in breast cancer death rate declines —
based on timing of mammography introduction in Europe — there are several reasons why the analysis
published in BMJ failed to do so:
1. The mortality data are contaminated with deaths attributable to breast cancer diagnoses that
occurred before screening was introduced. During the period 1986-1996 (and thus, also 19932003) half of the breast cancer deaths are attributable to a diagnosis before screening was even
offered, much less fully implemented. That leaves insufficient time to measure a population wide
effect.
2. Just because two nations share similar geography, does not mean their breast cancer mortality
trends are easily compared. Compared with Norway, Sweden had roughly 10 percent greater
breast cancer incidence during the study period. It was even greater before the study period
began. That would influence mortality rates over time — as mortality rates are a function of
incidence rates over time and their corresponding survival. The authors did not adjust for
incidence rate differences between comparison nations.
3. While Sweden began introducing screening in 1986, not all counties did so that year. Not all
women received a mammogram in 1986. It takes time to invite the population to screening. Full
implementation didn't occur until 1992-1993.
4. Not all women who develop breast cancer have been invited to screening. Not all those invited to
screening attend screening.
5. The study did not demonstrate how effectively mammography is functioning in comparison
countries. The effectiveness of mammography on a population-wide basis is influenced by the
attendance rate and the accuracy of the screening.
Women 40 or over increase their risk of dying from breast cancer by not getting annual mammograms.
Mammography also provides opportunity for a wider range of treatment options, and increases odds that
less aggressive treatment can be successful. This not only save lives, but quality of life as well.
The American College of Radiology and Society of Breast Imaging continue to recommend that women
get annual mammograms starting at age 40. Those with a family history of breast cancer (or other factors
that place them at elevated risk for the disease) should speak with their doctor about being screened
even earlier.
For more information regarding the importance of annual mammograms, to receive an annual reminder to
get a mammogram or to find an accredited mammography facility, visit
www.MammographySavesLives.org.
To speak with a mammography expert, please contact Shawn Farley at 1-703-6488936 or PR@acr.org.