'No Evidence' That Breast Cancer Screening Affects Death Rates Amongst Women

Breast cancer screening programmes have yet to show a reduction in the number of women who die from the disease, researchers said.

A new study suggests that there is "no evidence" that screening women for breast cancer has an effect on mortality.

The Breast Cancer Campaign said that 'conflicting findings from different studies can be confusing for women'

There has been fierce debate about the value of such screening programmes.

While mortality rates for breast cancer have significantly declined since the 1980s, some critics have said that breast cancer screening programmes do more harm than good and lead to many women undergoing unnecessary surgery.

In response to the controversy, the Department of Health commissioned an review into the risks and benefits in 2011. The independent panel concluded that there was a 20% relative reduction in mortality from breast cancer in women invited to screening.

But the latest research, published in the Journal of the Royal Society of Medicine, contests the findings.

The authors wrote: "We permuted the data in a number of different ways, over an observation period of 39 years, but the data show that, at least as yet, there is no evidence of an effect of mammographic screening on population-level breast cancer mortality."

The research analysed mortality trends across England before and after the introduction of the NHS Breast Screening Programme in 1988.

Researchers from the department of public health at the University of Oxford also specifically looked at mortality statistics from the Oxford region because it was the only area in the country which recorded all causes of death on the death certificate, not just the underlying cause, prior to the commencement of the programme.

They concluded that population-based mortality statistics for England do not show a past benefit of breast cancer screening.

Lead researcher Toqir Mukhtar said that while the new results do not rule out a benefit of breast cancer screening at the level of individual women, "the effects are not large enough to be detected at the population level".

"Measuring the effectiveness of mammography screening is a fundamental area of concern in countries which have established mammography screening programmes," she said.

"Clinical trials have indicated that several years have to elapse between the start of screening and the emergence of a reduction in mortality. 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."

Baroness Delyth Morgan, chief executive of the charity Breast Cancer Campaign, said: "While research into breast screening is welcomed, conflicting findings from different studies can be confusing for women.

"The most in-depth study of breast screening to date remains the recent independent breast screening review, which comprehensively looked at all available evidence. It concluded that screening does save lives by helping to detect breast cancers earlier.

"The quicker women are diagnosed the better their treatment options so we encourage all women to continue to attend screening when invited to do so."

Eluned Hughes, head of public health at Breakthrough Breast Cancer, added: "It's hard to unpick the individual factors that are helping us in the fight against breast cancer; declining death rates from the disease are likely due to a combination of better diagnosis, improved treatments, and - thanks to screening - earlier detection.

"There are clear limitations to this study, one of the most significant being it didn't compare mortality rates for women who chose to attend with those that did not, making the benefit of screening on mortality difficult to determine."

Professor Julietta Patnick, director of the NHS Cancer Screening Programmes, said: "The NHS Breast Screening Programme plays a key role in detecting breast cancer at an early stage, which gives women the best chance of successful treatment.

"The Department of Health recently commissioned an independent review, which evaluated the evidence for the benefits and harms of breast screening in an open and transparent way. The review panel concluded that the programme saves around 1,300 lives each year in the UK.

"All new evidence about the benefits and harms of breast cancer screening is kept under review to ensure that the breast screening programmes are based on the latest available evidence."

Professor Sir Michael Marmot, who led the independent review on behalf of the Department of Health, added:"The two biggest influences in trends on breast cancer mortality rates are changes in incidence - the causes of onset of new cases - and improvements in treatment. Against this background, it is difficult to estimate the effects of screening on breast cancer mortality from observational data such as these.

"In addition, comparing trends in mortality data, for example before and after the introduction of screening, or across different age groups or socioeconomic settings, is difficult due to inherent differences between these groups.

"It is for these reasons that we, as the panel of the independent review, relied on randomised controlled trials for the best estimate of the benefits of screening, over observational data like the kind reported here. After reviewing the available evidence, we concluded that the NHS breast screening programme confers significant benefit to women and should continue.

"Evidence suggested it offers a 20% relative risk reduction in mortality to women who were invited to participate in a 20-year screening programme. This equates to the prevention of around 1,300 deaths from the disease every year in the UK. "