The ongoing and often nasty fight over the merits of annual mammography screening for all women aged 40 and older has just heated up again.
Findings from a new study, published online Thursday in the British Medical Journal (BMJ), suggest that the decline in the number of breast cancer deaths that has occurred in developed countries over the past two decades is due more to better treatment and improvements in the efficiency of health-care systems than to breast cancer screening.
Advocates for annual mammography often point to the falling rate of breast cancer deaths as evidence that universal screening saves lives. Others, though, have questioned that connection, pointing to research that suggests better treatments, not mammography screening, is what’s improving the survival odds for women with breast cancer. They have also questioned whether the benefits of screening all women annually, particularly those aged 40 to 49, outweigh the risks, which include unnecessary biopsies and other treatments.
The new BMJ study, which was led by an international team of researchers, compared breast cancer mortality data from three pairs of countries with similar health-care services and levels of risk for breast cancer mortality. Northern Ireland was compared with the Republic of Ireland, the Netherlands with Belgium and Flanders, and Sweden with Norway.
The first country in each of those pairs introduced screening mammography 10 to 15 years earlier than the second.
The researchers chose this methodology because it had been used successfully before to show a clear link between the introduction of cervical cancer screening in Nordic countries and a drop in the death rate from that cancer.
After crunching the breast cancer data, the BMJ researchers found no statistically significant differences in the breast cancer death rates between those countries with long-standing screening programs and those that had introduced universal screening more recently.
Specifically, they found that between 1980 and 2006, deaths from breast cancer fell by 29 percent in Northern Ireland versus 26 percent in the Republic of Ireland; by 25 percent in the Netherlands versus 20 percent in Belgium and 25 percent in Flanders; and by 16 percent in Sweden versus 24 percent in Norway.
Interestingly, the study also found that the greatest drop in the breast cancer death rate was among women aged 40 to 49 — regardless of whether or not screening was available to them.
These findings suggest, said the study’s authors, that improvements in treatment and health-care systems “may be more plausible explanations” for the falling rates in breast cancer deaths that have been observed around the world in recent decades.
“Trends in breast cancer mortality rates varied little between countries where women had been screened by mammography for a considerable time compared with those where women were largely unscreened during that same period,” the study’s authors concluded. “… Our study adds further population data to the evidence of studies that have used various designs and found that mammography screening by itself has little detectable impact on mortality due to breast cancer.”
The study is available in full at the BMJ website.