A new UK study suggests screening for breast cancer does not reduce deaths from the disease. The study, which looked at nearly 40 years of breast screening, adds to the controversy surrounding whether it is screening or improvement in treatment that accounts for the fall in rates of death from breast cancer.
The researchers from the Department of Public Health at the University of Oxford, report their findings online in the June issue of the Journal of the Royal Society of Medicine.
For their study, lead author Toqir Mukhtar and colleagues analyzed mortality statistics recorded before and after 1988, the year that the National Health Service Breast Screening Programme began.
They could only include breast cancer deaths in the Oxford region because this was the only part of England where death certificates recorded all causes of death, and not just underlying cause, before the introduction of the screening programme.
Comparing the results with death rates for England as a whole, the researchers found no evidence, in nearly 40 years of the data, of a greater fall in deaths among women who underwent breast screening.
The findings contrast with a study reported in The Lancet in 2012 by an independent expert panel set up by the Department of Health that concluded patients who are invited for mammogram screening have a 20% lower relative risk of breast cancer death than those who are not invited.
However, that review also found that for every death prevented by breast cancer screening, three patients will be over-diagnosed and treated for the disease.
Mukhtar points out their study does not rule out that breast screening may benefit individual women, but any such effect is not big enough to show at the population level.
She also highlights the problems of trying to evaluate the effectiveness of mammogram screening when the last 20 years have seen enormous improvements in treatments and also in the technology used to do the screening. The effects of these changes should also be considered, she argues, adding that:
“Measuring the effectiveness of mammography screening is a fundamental area of concern in countries which have established mammography screening programmes.”
Mukhtar says clinical trials show that you have to wait several years after starting a screening programme before you see any reductions in deaths.
Nonetheless, she concludes:
“Yet our data shows that there is no evidence of an effect of mammographic screening on breast cancer mortality at the population level over an observation period of almost 40 years.”
In 2012, a Dutch study concluded that although treatments have improved, population-based mammography initiatives still save lives.