Cancer screening has never been shown to save lives, experts claim as false results causing deaths from needless treatments, along with suicides or heart attacks, are not being taken into account.
Researchers say that, whereas the harms of screening are certain, the benefits in overall mortality are unclear. The belief screening prevents early deaths is based on reductions in disease-specific mortality rather than overall mortality, which should be the benchmark against which screening is judged, they argue. Support for programmes that borders on fear-mongering has led to the public having an inflated sense of the benefits and discounted sense of the harms of screening, scientists from the Oregon Health and Science University write in a BMJ article.
The authors cite screenings of prostate and breast cancer as particular examples where further testing, overdiagnosis and overtreatment can cause more harm than good. Realisation of this in other areas has led to reversal or abandonment of a number of screening campaigns, including chest radiography screening for lung cancer and urine testing for neuroblastoma, they write.
The scientists say prostate-cancer testing yields numerous false positive results, which contribute to over one million prostate biopsies a year. These, in turn, are linked to serious harms, including admission to hospital and death as men diagnosed with prostate cancer are more likely to have a heart attack or take their own lives in the year after diagnosis.
Although studies regularly show women think that breast screening lowers their risk of getting breast cancer, a recent mammography review in the United State “did not show reduced breast cancer deaths when adequately randomised trials were analysed”, the scientists write.
Consideration of harms also becomes more important in the absence of clear overall mortality benefit, they add. To find out whether screening saves lives, they say investing in large trials that can determine overall mortality is “worth the expense compared with the continued cost of supporting widespread screening campaigns without knowing whether they truly benefit society”.
The team calls for “higher standards of evidence”.
However, the scientists said political will, financial resources, and public perception are “common hurdles” in building support for measures likely to be costly and take time and effort. They conclude: “We encourage healthcare providers to be frank about the limitations of screening – the harms of screening are certain, but the benefits in overall mortality are not. Declining screening may be a reasonable and prudent choice for many people.”
An accompanying BMJ editorial calls for more “transparent information” on cancer screening.
Samia al-Qadhi, chief executive at Breast Cancer Care, said the study added to the “mountain of conflicting evidence” on screening.
She added: “This ongoing confusion about the benefits and risks of screening means that women are unsure about whether to attend. It’s one of the reasons why the number of women going is declining.”
Dr Anne Mackie, director of screening at Public Health England, said: “NHS cancer screening and follow-up treatment does prevent or can at least delay some people dying from cancer.”
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