Blog
To screen or not to screen? Breast cancer screening in women 70-74 years
Tuesday May 1, 2018
SCENARIO: Mrs Smith is a 73-year-old widow. She has diabetes and osteoarthritis. Mrs Smith attends water aerobics twice a week. She asks her GP if she should have a screening mammogram.
The answer is probably yes, but let us consider.
Fact 1: Australian women are living longer with an average life expectancy of about 84 years.
Fact 2: Breast cancer is the most common cancer affecting Australian women and increasing age is one of the strongest risk factors.
Fact 3: Detection of breast cancers at an early stage by screening mammography provides the best chance of effective treatment.
Is this enough information to recommend screening mammography to all women aged 70-74 years?
What if Mrs Smith is 74 years and 10 days? What if Mrs Smith is 80 years?
BreastScreen Australia, the national population-based breast cancer screening program, recommends that women aged 50-74 years without any breast problems attend for free two-yearly screening mammograms.
The extension of the screening age from 69 to 74 years occurred in 2014 after a review of the program.
Women aged 40-49 years and 75 years and over are also eligible, but do not receive an invitation to attend.
Whilst screening mammography has been shown to be effective in reducing breast cancer mortality in women aged 50-74 years, there is little evidence of benefit in women 74 years and older. So, yes based on her age alone, Mrs Smith is recommended to have a screening mammogram at 73 years.
As Mrs Smith and other women in her cohort grow older, the decision whether to continue screening depends on a number of factors.
There is variability in the comorbidity status and life expectancy among older women. Some women will be healthy and active whilst others may have multiple health problems with diminished life expectancy.
Some women will want to continue cancer screening indefinitely.
It is not surprising that there is confusion amongst both the public and GPs about continuing screening mammography in this group.
The GP’s decision to recommend mammography or a woman’s decision to undergo screening needs to take into account comorbid conditions and the potential benefits and harms.
The most important benefit of screening mammography is an improvement in life expectancy. However, as rates of clinically slow-growing tumours and DCIS increase with age, older women are more likely to be harmed from over-diagnosis, defined as detection of tumours by screening that would not become clinically apparent during a woman’s lifetime or would not affect overall survival.
Over-diagnosis can lead to over-treatment, with the risks of breast cancer treatment increasing with age. Many older adults overestimate the benefits of screening and underestimate the harms.
In women over 74 years, the long-term benefits of screening may not be realised when there are competing causes of mortality.
As the first point of contact for health issues for many Australians, GPs have a key role in communicating the potential benefits and harms of screening mammography to older women. While the balance of benefits versus harms of screening are favourable for women up to 74 years, there is little evidence to support population screening in older women.
A reasonable approach to optimising the benefits of screening for older women is for GPs to individualise their advice based on comorbidity status and life expectancy.
A decision to stop breast cancer screening doesn’t mean abandoning health promotion, but refocusing on interventions more likely to be of benefit sooner. ■
