A group of doctors and health experts wrote to The Times urging women aged 70-79 who did not undergo routine breast cancer screening because of a computer glitch not to attend the catch-up breast screening appointments being offered to them. These doctors have accused the breast screening programme of “fear-mongering” and argue that the programme can do “more harm than good”.
What are the benefit and harms of breast screening in older women? A major independent review concluded in 2012 that screening by mammography benefitted some women, by preventing them from dying from breast cancer, and harmed others, by over-diagnosing cancers that would otherwise never have been detected or caused harm. They estimated that with three-yearly screening from age 50 to age 70, one breast cancer death would be avoided for every 180 women screened; and that one extra case of breast cancer would be diagnosed for every 60 women screened.
Nevertheless, there is little direct evidence as to the additional benefit and harm of having one last screen at age 70. The main argument against screening older women is that because they have shorter life expectancy they benefit less. This argument is based on measuring benefit in terms of (quality adjusted) years of life gained (known as QALYs). If two women diagnosed with breast cancer are prevented from dying of breast cancer at age 75 and one dies at 80 and the other at 90, then one gained 5 years of life and the other 15. The quality of the years of life gained must also be taken into consideration. Using this logic health economists assume that, all things being equal, it is less cost effective to screen older women. Additionally, as the expectation of additional life decreases so the risk of over-diagnosis increases. For example, screening a 100-year-old woman would be ridiculous because the chances are she would not live long-enough to die from breast cancer and her final years could be burdened with cancer treatment.
I said, assuming “all things being equal”. But all things are not necessarily equal. Rates of breast cancer diagnosis and death increase with age. And, despite many people believing that breast cancers in older women tend to be less aggressive, a higher proportion of elderly women with breast cancer die from their cancer. This is likely to be partly due to their cancer being diagnosed at a more advanced stage when treatment is harder, and partly because elderly women with other health problems may not be well enough to have some of the more aggressive treatments. Whatever the reason, the benefit of finding a breast cancer at age 70 rather than at age 77 may be greater than the benefit of finding a cancer at age 60 rather than at age 67.
Health economists may consider the benefit of a breast cancer death avoided at age 66 to be much greater than the benefit of a breast cancer death avoided and at 76, but a healthy 70-year-old woman may not agree. The benefit of not needing chemotherapy and of not dying from brain metastases are largely independent of age. And the chance that a single additional screen will have such a benefit at 70 is probably at least as great as the chance per screen between ages 50 and 67.
So how should a woman balance the harms of over-diagnosis with the benefits of not dying from breast cancer? That is a difficult question and one that is impossible to answer on behalf of someone else. It is ultimately a very personal decision. But people should be given honest information.
What are the harms of over-diagnosis?
Firstly, there is the harm of being told you have cancer. For many that diagnosis will affect how they feel and think for the rest of their life. Then there is the treatment. Most screen-detected cancers are treated with a lumpectomy (breast conserving surgery) plus hormone therapy. Some will also receive radiotherapy.
These treatments can lead to restricted arm movement and shoulder pain. Very few women with an over-diagnosed cancer will be treated with chemotherapy or mastectomy: 71% of women with screen-detected cancers in their 70s have breast conserving surgery (and only 5% are not treated surgically) compared to 40% of those with symptomatic cancers (and 46% are not treated surgically but receive only drugs because their cancer is too advanced to try to cure). Thus, whilst a harm of screening is that more women will be diagnosed with breast cancer and will have a lumpectomy and five-years of hormonal treatment, a benefit may be that fewer women who go for screening have a mastectomy or receive chemotherapy.
So, what would I advise if you receive one of the catch-up invitations? If you are fit and healthy accept the gift. Yes, you are more likely to be diagnosed with breast cancer if you do, but you are also less likely to die from it. Think of it this way. For every three extra women who receive treatment because of screening, one woman will be cured of a breast cancer that would otherwise have killed her. Not many medical interventions can claim such a big effect. Most patients would accept far more toxic treatments if they offered an even 10% chance of saving their life.
Want an update on this story? Both the National health Executive and the Guardian have interesting follow-ups.
For further thoughts from ‘experts’ on this story: http://www.sciencemediacentre.org/expert-reaction and https://medium.com/wintoncentre/
The views expressed are those of the author. Posting of the blog does not signify that the Cancer Prevention Group endorse those views or opinions.
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