Breast screening: More harm than good?

9th December 2011 - A new study by researchers at the University of Southampton supports the claim that the introduction of breast cancer screening in the UK may have caused more harm than good.

Harms included false positives (abnormal results that turn out to be normal) and overtreatment (treatment of harmless cancers that would never have caused symptoms or death during a patient's lifetime).
In the light of the findings study author, Professor James Raftery, told us by e-mail what he recommends for the NHS screening programme: "That it informs women more fully than present on the risk of harm due to breast cancer screening."

Catherine Priestley, Clinical Nurse Specialist at Breast Cancer Care told us by email: "We know that prompt detection of breast cancer can lead to more effective outcomes, so until it is possible to accurately determine the progression of cancers found through mammograms, screening remains an effective option for detecting breast cancer as soon as possible."  

An independent review of the NHS screening programme is currently underway.

Under the present system women in the UK aged between 50 and 70 are invited for screening. Although the process saves lives, it is not possible to say how many. According to Cancer Research UK, the figure is thought to be between 300 and 1,400 each year.

Updating original estimates

This latest study shows that the harms of screening largely offset the benefits up to a period of 10 years, after which the benefits accumulate, but by much less than predicted when screening was first started.

The Forrest report in 1986, which led to the introduction of breast cancer screening in the UK, estimated the number of screened and unscreened women surviving each year over a 15-year period.  Costs and benefits were measured but not harms.

Since the Forrest report, the harms of breast cancer screening have been acknowledged. So, researchers at the University of Southampton set out to update the report's survival estimates by combining the benefits and harms of screening in one single measure.

The results are based on 100,000 women aged 50 and over surviving by year up to 20 years after entry into the screening programme.

Inclusion of false positives and unnecessary surgery reduced the benefits of screening by about half. The best estimates generated negative net QALYs (quality adjusted life years-
a combined measure of quantity and quality of life) for up to eight years after screening and minimal gains after 10 years.

After 20 years, net QALYs accumulate, but by much less than predicted by the Forrest report.

The study from Southampton has been published on bmj.com

Explanation

The authors say the meaning and implications of over diagnosis and overtreatment need to be much better explained and communicated to any woman considering screening.