Issue 41 / 28 October 2013

SHARED decision making between doctors and patients is the best approach to deciding if the benefits of undergoing cancer screening outweigh the risks of overdiagnosis for any particular patient, says a leading public health expert.

Professor Chris Del Mar, professor of public health at Bond University and a member of the Royal Australian College of General Practitioner’s Red Book preventive guidelines committee, said there were “a lot of raging controversies within the profession” about cancer screening, making it “a very confusing and disputed area”.

Professor Del Mar said one answer was for clinicians to engage in shared decision making with their patients.

“You need to put all those things on the scales to decide which way the scales are going to swing with each patient and for each screening intervention”, he said.

It was also crucial for clinicians to seek patient permission before doing a screening test. Professor Del Mar said data had shown that some doctors were adding prostate-specific antigen screening tests to a battery of other tests without advising their patients.

“This is bordering on medical negligence, particularly in light of information about potential harms”, he said.

Professor Del Mar was commenting on a US survey that found that few clinicians advised patients of the potential for harm with cancer screening.

The research letter, published in JAMA Internal Medicine, found that of 317 US patients aged 50–69 years only 9.5% said their physician had told them about the risks of overdiagnosis and overtreatment in cancer screening. (1)

About half of all survey participants (51%) told the researchers that they would not undergo screening that resulted in more than one overtreated person per one life saved from death due to cancer.

The researchers said the results indicated that clinicians’ counselling on screening fell short of patient expectations and called for improved education for health professionals about screening risks, and more detailed reporting of overtreatment risks in medical journals.

Professor Paul Glasziou, professor of evidence-based medicine at Bond University, said that in the absence of an agreed methodology to quantify the risks of harm from cancer screening, it would remain difficult for clinicians to effectively provide this information to patients. (2)

“Surveys suggest that patients want more detail, more quantification of the chances of being [overdiagnosed]. Doctors misread that, but they also have difficulty getting the numbers”, he said.

Professor Glasziou said he was not surprised that participants in the JAMA Internal Medicine study reported a lack of discussion about overdiagnosis, but suggested that 9.5% may be an underestimate.

“Given that the rates of overdetection and overdiagnosis in screening have only been quantified in the last decade, the 9.5% of patients reporting it was discussed with their doctor is not unexpected. This is likely to be an underestimate as patients may not recall that it was discussed, particularly if the last consultation was some time ago,” he said.

Professor Del Mar said clinicians had only recently come to realise the “quite significant threat” that came with cancer screening.

“It’s only recently that epidemiologists have been able to calculate the numbers and show that overdiagnosis is a problem and that the downstream consequences of overtreatment are likely to be happening as well”, Professor Del Mar said.

Improved medical education about the potential for overdiagnosis with cancer screening was needed, he said. However, he agreed that there were difficulties in communicating these risks to doctors.

Professor Glasziou said the responsibility for delivering better information to patients rests not only with clinicians but also with the media.

“We do need to have a higher awareness of this in the community and I would see it as not just as a doctor–clinician responsibility. It also needs to be a media responsibility,” he said.

“Patients expect that all cancers detected are consequential cancers. The idea of overdiagnosis is not on the media and public radar.”


1. JAMA Intern Med 2013; Online 21 October
2. Lancet Oncol 2013; 8: 1129-1138


Do doctors have access to enough information to discuss the pros and cons of cancer screening with patients?
  • No - but should be raised (45%, 30 Votes)
  • Yes (39%, 26 Votes)
  • No - too uncertain (15%, 10 Votes)

Total Voters: 66

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3 thoughts on “Cancer screening a shared decision

  1. Dee Brown says:

    Informed consent and even consent itself is largely academic in women’s cancer screening, there is a LOT of pressure to screen and the only information provided is one-sided and paternaltistic..scare campaigns, slogans and celebrity endorsement. It’s impossible for a woman to make an informed decision about pap tests and mammograms unless she does her own research, and if she chooses to decline, must defend her decision in the consult room. 

    The fact is our cervical screening program is outdated, has not followed the evidence and seriously over-screens, this greatly increases the risk of a false positive/over- treatment/biopsies for no additional benefit. (to women) Women who wish to test should watch the Finns and Dutch, they follow the evidence, putting women first. The Dutch will scrap their 7 pap test program and offer instead 5 HPV primary tests (or women can use a self test device) at ages 30,35,40,50 and 60 and only the roughly 5% who are HPV+ will be offered a 5 yearly pap test. (until they clear the virus) This will save more lives and take most women out of unnecessary pap testing and harms way. We spend millions pap testing and “treating” when MOST women are not even at risk, why? 

    Over-diagnoss in breast screening and uncertainty of benefit has been kept from women too. Screening programs should be monitored by an independent group like the Nordic Cochrane Institute, and should follow the evidence and respect informed consent, screening targets and target payments to GPs are inappropriate. Our programs and the way they treat women reflects poorly on our medical profession, we should start respecting women as independent and competent individuals, as we do with men and prostate screening.


  2. John Moore says:

    The ultimate crime in medicine is to turn well people into sick people.

  3. Nicole payne says:

    I don’t know  if doctors still hold the pill hostage until they submit to a pap smear but this practice was rampant. Not only do doctors not give give out any information on the pros and cons of screening but if a patient tries to refuse, they can be actually ridiculed. A friend of mine was called  a “silly girl” for refusing a pap smear just recently. A lot of retraining of doctors and their attitiude needs to be implemented including advising the doctors they they may be at risk of litigation if they take it upon themselves to decide on the patients behalf which screening tests they should have. Perhaps only that will stop this unethical practice.

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