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Calls to reduce breast cancer screening age spark overdiagnosis fears


Anastasia Tsirtsakis


24/02/2021 5:01:59 PM

New research suggests screening from age 40 has better outcomes for reducing breast cancer mortality. But is that really the case?

Breast cancer screening test.
GPs have a critical role to play in timely investigation and diagnosis of breast cancer, says Dr Alia Kaderbhai.

Breast cancer is the most commonly diagnosed cancer among women around the world, with Australia ranked among the top 10 countries with the highest rates.
 
Now new research suggests developing a breast screening strategy targeting women from age 40, based on a baseline breast density measure, could be the most effective way to reduce breast cancer mortality.
 
Using a microsimulation model, researchers from the University of Texas MD Anderson Cancer Center and Fred Hutch Cancer Center, compared the health outcomes and cost-effectiveness of seven breast cancer screening strategies:

  • no screening
  • biennial screening for women aged 50–75 (without dense breasts)
  • triennial screening for women aged 50–75 (without dense breasts)
  • four density-stratified strategies (two with baseline mammogram at age 40 and the other two at age 50 – both cohorts with dense breasts)
The findings suggest screening women at age 40 with a baseline breast density assessment, followed by annual screening for women with dense breasts aged 40–75, has the greatest reduction in breast cancer mortality.
 
While the best strategy for women aged 50–75, without dense breasts, is screening every two years.
 
In Australia, women receive an invitation to take part in the Federal Government’s BreastScreen Australia Program from age 50 every two years, free of charge. However, women can access free screening from age 40 on a case-by-case basis.
 
Dr Alia Kaderbhai, Chair of the RACGP Specific Interests Breast Medicine network, told newsGP when weighing up the risk versus benefit for starting screening at age 40, the rationale is unjustified.
 
‘Starting screening from age 40 onwards is unlikely to significantly reduce the number of late stage tumours [those bigger than 2 cm],’ she said.
 
‘[That] means that breast screening in this way is unlikely to reduce breast cancer mortality or lead to less invasive treatment.’
 
In addition to considering health outcomes, the study suggests a density-stratified strategy is also cost-effective, yielding an incremental cost-effectiveness ratio of US$36,200 (AU$45,400) per quality-adjusted life year (QALY) when compared to non-density-stratified biennial screening at age 50–75.
 
While that may be the case, Dr Kaderbhai says the association of more frequent screening with false positives and overdiagnosis is cause for concern.
 
‘We know that with increased screening we can “over-diagnose” patients – [this] refers to detection of cancers that might never have progressed or become symptomatic in a patient’s lifetime,’ she said.
 
‘Already about one in three breast cancers detected in women offered screening are likely over-diagnosed.
 
‘There is also a risk of about 10% for false positive results. This leads to unnecessary investigations that are sometimes invasive, as well as increased anxiety for men and women.’
 
Dr Kaderbhai’s concerns are in line with those expressed by experts from the University of California, who penned an editorial to accompany the research.
 
They argue that while breast density is an important risk factor to include in risk-based screening strategies, that it should be combined with age and other risk factors that optimise benefits and minimise harms.
 
Until a more robust risk-based strategy is identified, they say data supports screening from age 50–74, every two years.
 
Dr Kaderbhai says the main issue is to ensure that the health practitioner, often the patient’s GP, is trained in being able to accurately interpret and communicate breast density classification.
 
‘Presumably, the report is sent back to the GP and patients will be seeking advice about what the breast density information means for them in terms of risk,’ she said.
 
‘So we need to ensure that the person receiving the information knows how to interpret this information and what they should be telling their patients.’
 
When it comes to women participating in the screening program, Dr Kaderbhai says GPs ‘play a crucial role’ to ensure timely investigation and diagnosis of breast cancer.
 
A consequence of the coronavirus pandemic was a disruption to all cancer screening, with data from the Victorian Cancer Registry showing that cancer pathology notifications declined for all tumour streams by up to 27% from 1 April to 30 June.

‘This is partly due to the recent temporary suspension of activity of BreastScreen Australia, coupled with symptomatic women delaying presentation or not responding to routine screening invitations,’ Dr Kaderbhai said.
 
‘BreastScreen has now reopened, [but] with reduced screening capacity, which has been necessary in order to implement COVID-19 safety measures.’
 
She says GPs should be encouraging all eligible women to take part in screening, but to assess all patients for risk factors – including age, family history, obesity, smoking, alcohol intake and physical activity levels.
 
‘It is pertinent to remind health professionals that a screening mammogram is used to check for breast cancer in women who have no signs or symptoms,’ Dr Kaderbhai said.
 
‘[But] we are often the first port of call for women who present with a new breast symptom – such as a lump or nipple discharge,
 
‘It is the responsibility of the GP to then ensure timely investigation, diagnosis and appropriate referrals are carried out to optimise treatment outcomes for patients.’
 
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