Routine mammography programs that screen women for breast cancer have virtually no effect on death rates, concludes a new study that will likely add to the contentious debate about the benefits of such screening programs.
In a study published this week in the British Medical Journal, researchers from Denmark and Norway said they had found no evidence that screening women for breast cancer reduces deaths.
They say their study found that reductions in breast cancer death rates were about the same in regions that had screening programs and in areas without such programs.
Leader researchers Karsten Jorgensen of the Nordic Cochrane Center in Copenhagen said she wasn't particularly surprised by her findings.
"Our results are similar to what has been observed in other countries with nationally organized programs," she said.
"It is time to question whether screening has delivered the promised effect on breast cancer mortality."
It is important to note that the study looked at mammography screening programs -- not diagnostic mammography, which is used to investigate a breast lump or other abnormality.
Mammography screening programs screen otherwise healthy women for tumours. In Canada, it is recommended that all women aged 50 to 69 have a screening mammogram every two years.
Critics of screening programs often contend the programs can be more harmful than helpful, in part because of false positive test results, which can lead to worry and unnecessary further testing. Critics insist the risks of such screenings are not outweighed by the benefit of preventing more deaths.
This new study was undertaken by researchers who wanted to know whether a 2005 study that found a 25 per cent reduction in breast cancer deaths in parts of Denmark after the introduction of mammography really was due to the screening.
They looked at data on all Danish women recorded in the Cause of Death Register and Statistics Denmark database between 1971 and 2006. It included 17 years in which there were universal breast-cancer screening programs for women aged 55 to 74 in only two areas: Copenhagen and Funen County. In the rest of the country there was no organized screening.
They found that in older women -- those aged 55 to 74, who are considered most likely to benefit from screening -- breast cancer deaths fell by 1 per cent a year in screened areas and by 2 per cent a year in non-screened areas, a difference not considered significant.
In younger women -- those aged 35 to 54, who are considered too young to benefit from screening -- breast cancer mortality declined by five per cent a year in screened areas and by 6 per cent a year in non-screened areas during the same period.
In the 75-and-over age group, there was no change in mortality in any area.
The researchers also found that breast-cancer deaths dropped steadily in the 10 years before screening programs began, likely because of better treatment as well as changes in breast cancer risk factors among the women.
The Canadian Cancer Society recommends that all women aged 50 to 69 should have a breast exam by a doctor at least every two years and a screening mammogram every two years.
It says women aged 40 to 49 should undergo a clinical breast exam, but should also be able to have mammogram screenings if they are referred by a doctor or a nurse practitioner.
"There is some suggestion that women aged 40¬49 could benefit from regular mammography, but the issue is confusing because there are conflicting results in the research and conflicting messages from various health and advocacy groups," the Cancer Society notes on its website.
