The UK surgeon whose work led to the introduction of bowel cancer screening tests has warned the practice has potential to be a “dangerous tool”.
In his keynote address to the Public Health Association of Australia’s Cancer Screening Symposium, Prof Robert Steele called for greater public awareness that screening is a “double-edged sword”.
While national screening programs for bowel, breast and cervical cancer have saved lives due to early detection, and have helped to reduce disease rates, Steele said the harms of screening were seldom addressed with patients.
“They [patients] can be harmed by false reassurance, they can be harmed by investigations or treatment that go wrong, or indeed they can be harmed by treatment that was unnecessary because of overdiagnosis,” he told the conference in Melbourne on Tuesday.
Australia’s peak independent cancer authority, the Cancer Council, is among the organisations to recognise overtreatment and overdiagnosis is occurring due to expanding disease definitions and lower diagnostic thresholds. It occurs when benign abnormalities are detected due to screening and tests becoming more sophisticated, leading to patients sometimes getting major treatment for conditions that may never have gone on to cause symptoms.
“It’s crucially important that we are absolutely clear that the benefit provided by screening program is not outweighed by the harm,” Steele said. “And the problem is, it’s not always absolutely obvious when harm outweighs benefit, which makes screening a really dangerous tool and something that we have to handle very carefully indeed.”
Research quantifying the harms of screening programs should be a priority to ensure net benefit for patients, he said.
Steele, who stepped down as the chair of UK National Screening Committee in 2022 after a six-year tenure, said it was important to note the implications and potential harms of overdiagnosis differ between cancers. For example, prostate cancer is more prone to overdiagnosis, with some men diagnosed with and undergoing unnecessary treatment for cancers that may not go on to cause symptoms or threaten their life. But for cervical cancer, early detection is crucial.
Steele said while some overdiagnosis in cancer screening was “inevitable,” patients deserve to know the full range of risks and benefits so they can make informed choices about their treatments.
“It’s a difficult balance. What you don’t want to do is frighten people off so they don’t participate in screening, but they also need to know what the downsides to screening are,” he said.
“If it’s presented in a balanced fashion, it should be possible to maintain good uptake of screening with informed choice.”
The conference also heard about advances in screening, with lung cancer screening for high-risk individuals to be introduced in Australia in 2025.
And preliminary results from the largest randomised control trial conducted in Australia, presented at the conference, suggest that human papillomavirus (HPV) test-based screening is more effective at detecting pre-cancerous changes than the pap smear program it replaced in 2017 as part of the National Cervical Screening Program.
The HPV test is generally conducted every five years to detect the virus, which can lead to cell changes in the cervix that can cause cancer. The old pap smear test needed to be conducted every two years and looked for abnormal cell changes.
Cervical cancer is one of the most preventable cancers and most women diagnosed are those who have missed screening.
The conference heard that the Compass Trial, led by the Daffodil Centre and the Australian Centre for Prevention of Cervical Cancer, recruited 76,000 women and found the increased effectiveness of HPV screening applied regardless of vaccination against the virus.
It means more women are being treated before abnormalities can develop into cancer, which requires more invasive treatments.
