New research has indicated that the NHS breast screening programme has lower rates of overdiagnoses of cancer than originally thought.
The new study, funded by the National Institute for Health and Care Research and led by a team from Queen Mary University of London, analysed 57,493 cases of breast cancer diagnosed in 2010 or 2011, and matched them with 105,653 controls.
The researchers calculated how many cancers were diagnosed as a result of the breast screening programme in women aged between 50 and 77, and then compared this with the number of cancers diagnosed in women of the same age range, who were not part of the screening programme.
The extra cases in the women who participated in the screening programme were then used as an approximation for how many cancers are overdiagnosed.
The study team found that the estimated number of cases of overdiagnosis in women attending all appointments in the three-year screening programme was just under three in every 1000 – this translated to an estimated 3.7% of cancers detected by the programme being over overdiagnosed.
This is much lower than previous research has suggested, with other studies estimating that overdiagnosis ranges from just under 5% to more than 30%. Because of this, the researchers concluded that the breast screening programme has caused – at worst – a “modest” overdiagnosis of breast cancer in England.
Professor Stephen Duffy, joint lead investigator, said: “These results provide some reassurance that participation in the NHS breast screening programme confers only a low risk of an overdiagnosed breast cancer.
“Along with the results of our previous study of the effect of screening on breast cancer mortality, this indicates that the benefit of screening in preventing deaths from breast cancer outweighs the small risk of overdiagnosis.”
The intention behind the screening programme is to detect breast at the earliest possible stage, when they are easiest to treat. However, this carries the risk of potentially harming women who are treated unnecessarily for cancers that are extremely slow-growing and would never have caused any problems during a woman’s lifetime.
It is impossible to tell how fast a cancer will grow when it has been diagnosed, meaning they must all be treated, but treatments like radiotherapy or surgery can have serious side-effects.
More information on the results of the study can be found here.
