Issue 8 / 9 March 2015

MESSAGES about cancer screening programs in Australia are biased towards the benefits and minimise the risks of overdetection, according to leading researchers.

Associate Professor Tammy Hoffmann, a clinical epidemiologist in the Centre for Research in Evidence-Based Practice at Bond University, told MJA InSight there had been a number of studies looking at the content of cancer screening letters and invitations, and all concluded that there was usually little to no information about harms.

Professor Hoffmann said multiple factors had caused the lack of information being provided on screening risks, including the objectives of cancer prevention organisations, which might view participation rates as a primary measure of success.

“Their representatives are often dismayed by attempts at getting a more balanced, informed approach”, because it was seen as counterproductive to increasing the number of people getting screened, she said.

Professor Hoffmann was responding to a UK study published in The BMJ that assessed the level of overdetection people would find acceptable in screening for breast, prostate and bowel cancer. (1)

Overdetection was defined as the diagnosis of a cancerous lesion through screening that would otherwise not have caused symptoms or early death. In the case of breast cancer screening, overdetection resulted in more breast surgery and deaths from cardiovascular disease, as well as secondary cancers after radiotherapy, the study authors wrote.

Their research was based on an online survey of 1000 adults who were presented with information about each cancer and two screening scenarios: one indicating a 10% reduction in cancer-specific deaths and the second indicating a 50% reduction.

The authors found a large variability in the level of overdetection that people would accept. Across all scenarios, 4%-7% of respondents indicated they would accept no overdetection, compared with 7%-14% who found it acceptable for overdetection in the entire screened population.

The authors said their results highlighted that people should be more informed about the risk of overdetection before deciding to participate in a screening program.

Professor Chris Del Mar, professor of public health at Bond University and a coordinating editor of the Cochrane Collaboration, said one reason the harms of screening were not well publicised and understood was the ongoing lack of consensus among researchers.

Professor Del Mar believed shared decision making, as outlined in an article he coauthored in the MJA last year, could be a useful tool for clinicians to help patients make decisions about screening. (2)

He said this approach would better enable doctors to clearly explain to patients the key numbers and facts underscoring the pros and cons of cancer screening.

The BMJ has also published an analysis by Professor Alexandra Barratt, a professor of public health at the University of Sydney, discussing the evolving debate on overdiagnosis in mammography screening. (3)

She said agreement between experts about overdiagnosis was urgently needed so that women could be better informed, and that mammographic technology should be restrained until incremental net improvements in health outcomes were demonstrated.

Future public communication initiatives must focus on raising awareness of overdiagnoses in relation to breast, prostate, lung and thyroid cancers, Professor Barratt stated in her analysis.

Professor Kirsten McCaffrey, a NHMRC research fellow at the University of Sydney’s School of Public Health, told MJA InSight Australia should follow the UK’s lead and develop standard guidelines to ensure data on screening were delivered consistently and objectively, “rather than using persuasive messaging to promote uninformed participation”. (4)

However, Sally Crossing, chair of Cancer Voices NSW, told MJA InSight she still believed the benefits of early detection outweighed the harms of screening, especially for breast cancer, and was concerned these studies would unnecessarily scare women away from mammograms.

Ms Crossing was diagnosed with breast cancer in 1995. She said surgery was considered a harm of screening, but “I’m still here 20 years later because my cancer was detected early and treated”.

She believed a problem with the current research into overdetection was that it focused too much on epidemiological data, rather than the experiences of individuals.  

“As a consumer, you’re far more worried about having a small lump that might turn into a big lump rather than risks of overdiagnosis”, she said.

Ms Crossing said the perspective of the consumer must feature in any future screening awareness initiatives.

1. BMJ 2015; Online 4 March
2. MJA 2014; 201: 35–39
3. BMJ 2015; Online 4 March
4. Public Health England ; NHS cancer screening programmes

(Photo: shutterstock)

3 thoughts on “Screening needs “balance”

  1. Randal Williams says:

    I certainly saw the downside of breast screening,  patients subjected to unnecessary (as it turned out ) worry and inrterventional procedures for benign lesions picked up on MMG or U/S.  Also prostate biopsies for ultimately benign lesions causing septicaemia.  Screening for cancer is the “darling’ of many charitable funds and is politically correct in our community, as a result I think the downsides are under emphasised.

  2. John Boxall says:

    It seems to me that advocates of screening tests will always quote statistics that screening for that particular disease results in reduced mortality from that condition. I am happy to accept that, but what they don’t quote is what difference does screening for a particular disease make to the overall mortality  It seems to me that the answer can be minimal suggesting if one does not die from the disease being screened for due to successful treatment, something else is likely to kill us in the same time frame.  This unfortunately is not always addressed by the advocates of screening programs.

  3. Debra Brown says:

    Screening should only be introduced after randomised controlled trials are completed, the results reviewed by an independent body, and the programs must change over time with the evidence. It must also focus on the interests of the target group and respect informed consent. I haven’t seen anything like that in women’s cancer screening. I get the impression women are just expected to screen when ordered to do so (and scolded if we don’t). The focus appears to be coverage and reaching targets.

    There is a higher ethical responsibility with screening to help as many as possible, but also to minimise the negative impact on the people who cannot benefit (almost all of us with cervical screening). I noted the recent visit by Peter Gotzsche, head of the Nordic Conchrane Institute, was described in our papers as a visiting “Danish professor” with “some controversial views on breast screening”. This discussion is advanced overseas, the first NCI report was released over 10 years ago. Here we have Breast Screen using Jo Hall to urge women to screen: “it takes 10 minutes, it’s with a woman and it’s free”, hardly respecting informed consent (what about choice, overdiagnosis, do the risks of screening exceed the benefit?).

    Fortunately, women can get real information from overseas sources. Evidence-based cervical screening is found in The Netherlands and Finland. Our program is excessive, we have huge over-treatment/excess biopsy rates as a result. Our proposed new program will continue to side with excess. We use scarce funding on these programs, they should operate as efficiently/effectively as possible, excess/non-evidence based screening is unhelpful and often, harmful.

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