Cancer screening largely fails to extend lifetime, finds major study

The belief that cancer screening saves lives by extending lifetime is not substantiated by evidence, except when it comes to one type of lower bowel cancer test, researchers have found.

Researchers found that only colorectal cancer screening with sigmoidoscopy may extend a person’s lifetime, with approximately three months gained. 

The study, published yesterday, was based on a meta-analysis of 18 long-term randomised clinical trials which involved over 2.1 million people.

The all-cause mortality, which is death due to any cause, and estimated lifetime gained was analysed for six commonly used screening tests for breast, colorectal, lung, and prostate cancers. 

These included mammography, colonoscopy, sigmoidoscopy, faecal occult blood testing (FOBT), computed tomography, and prostate-specific antigen testing. 

The study found that sigmoidoscopy prolonged lifetime by 110 days, but faecal testing and mammography did not prolong life. 

Prostate cancer screening also prolonged life by 37 days and lung cancer screening by 107 days, however these results were ‘uncertain estimates’. 

The authors said: ‘Although our meta-analysis suggests that claims that screening saves lives are not substantiated by the current best available evidence, we do not advocate that all screening should be abandoned. 

‘Screening tests with a positive benefit-harm balance measured in incidence and mortality of the target cancer compared with harms and burden may well be worthwhile.

‘However, organisations, institutions, and policymakers who promote cancer screening tests by their effect to save lives may find other ways of encouraging screening. 

‘It might be wise to reconsider priorities and dispassionately inform interested people about the absolute benefits, harms, and burden of screening tests that they consider undertaking. Our estimates may serve that purpose.’

They also highlighted that without screening some patients may have died of cancer because it would have been detected at a ‘later, incurable stage’, and as such these people ‘experience a gain in lifetime’. 

However, they warned that there are potential harms linked to screening, citing the example of colon perforation during a colonoscopy.

Professor of cancer epidemiology at the Cedars-Sinai Medical Center Professor Paul Pharoah said in response to the study that the ‘common claim that screening saves lives is not justified by the available data’. 

He said: ‘There is nothing fundamentally new about their findings: previous publications have provided estimates of the relative risk of all-cause mortality associated with screening.  The authors of this paper have simply converted these relative risks into absolute risks.

‘It has been described many times before that the reduction in all-cause mortality from different cancer screening tests is very small.  

‘However, screening for any one cancer would only be expected to reduce mortality from the cancer being screened for and any all-cause mortality reduction would be small at best. 

‘Demonstrating a small reduction in all-cause mortality is very difficult from a statistical standpoint.’

In the UK, the NHS offers free screening to certain patient groups for bowel cancer, breast cancer, and cervical cancer.

Last week, Pulse reported that the UK National Screening Committee will soon consider six different proposals for future prostate cancer screening, which is not currently administered under a national programme.

Earlier in the month, GPs – including one of NHS England’s medical directors – raised concerns about communication from the Government encouraging men over 50 to check their risk of prostate cancer, saying it was ‘promoting’ unofficial prostate cancer screening.

 A study by University of Bristol researchers recently found that NHS screening has reduced the incidence of cancer in the lower bowel in England by roughly 15%.