The NHS computer error that has resulted in some 450,000 women aged around 70 not having received an appointment for a final breast screen is obviously, and understandably, deeply worrying for the women concerned. Predictably, the media have headlined the estimate that up to
270 of them may have developed cancers that are more advanced and difficult to treat than they would have been if diagnosed earlier. But this depends on a number of assumptions. Leaving aside the fact that this is the upper limit of an estimated 135-270 range (compare the "up to" speeds quoted by ISPs - how many customers achieve them?), the situation, as usual, is more complicated than the headlines imply.
has a good discussion of the question (Why breast screening error stories are getting death stats wrong
). This article makes the important point that, for some women, the failure to notify them may have done them a favour. The current NHS estimate is that, for every 200 women in the 50-70 age range screened, one will be spared an early death but three will have unnecessary treatment for cancers that would not have been a problem in their lifetime.
... it means that up to 800 women may have been saved from harm by not sending them their final screening appointment letter, as they avoided possible reduction in their life expectancy through unnecessary treatment.
The New Scientist
article makes the important point that the women who received unnecessary treatment would never know this and would presumably be forever grateful, believing that their lives had been saved by the 'harrowing treatment process'. So this is an 'invisible' harm that is difficult to quantify.
The BMJ of 24 November 2012 has a Cochrane systematic review and metanalysis that questions the value of routine health checks. Not only do they fail to prevent death or illness, they may also cause harm through unnecessary investigations or treatment.
We did find that health checks led to more diagnoses and more medical treatment for hypertension, as expected, but, as these did not improve mortality or morbidity, they may be considered harms rather than benefits.
The same issue of the BMJ also has a piece about screening for breast cancer. It reports an article in The New England Journal of Medicine
which finds that screening has led to the overdiagnosis of breast cancer in 1.5 million women in the USA in the last 39 years. Mammography only marginally reduced the rate at which women presented with advanced cancer. Although death from breast cancer has reduced considerably over this period, the reduction is mainly due to better treatment, not screening.
Here are a couple of quotes from the article in the NEJM.
Our study raises serious questions about the value of screening mammography. It clarifies that the benefit of mortality reduction is probably smaller. and the harm of overdiagnosis probably larger, than has been previously recognized.
Although no one can say with any certainty which women have cancers that are overdiagnosed, there is certainty about what happens to them: they undergo surgery, radiation therapy, hormonal therapy for 5 years or more, chemotherapy, or (usually) a combination of these treatments for abnormalities that otherwise would not have caused illness.
Finally, there is an article citing a report from the University of Minnesota which says that the effectiveness of 'flu vaccination has been greatly overestimated, at least for the over-65s for whom it is mainly recommended. There is no harm in having the vaccine, but it should certainly not be made compulsory fo health workers, as is increasingly happening.
The current issue of the BMJ reports the recommendations of the US Preventive Services Task Force, an independent body of 16 experts. They say that the PSA test should not be used to screen men for prostate cancer because it is unlikely to save lives and can cause harm.
The widespread US practice of annual PSA-based screening for prostate cancer in men aged 50 years and older is not supported by results from randomized controlled trials. PSA-based screening may modestly reduce prostate cancer mortality; this absolute benefit is small relative to other causes of death in this age group and is associated with substantial harms.
The potential harms from unnecessary investigations and treament include erectile xysfunction, urinary incontinence, bowel dysfunction, and death.
What is particularly interesting about this report is the delay that attended its publication. The group had made its recommendations in 2009 and 2010, but not until an article appeared in the New York Times
were they made public, nearly two years after they were made. I wonder why.
It's exactly a year since I last wrote about PSA screening for prostate cancer. This week's BMJ has an article about it ("Prostate screening: is the tide turning against the test?"). This is about an article in The New York Times by the discoverer of PSA, Richard Ablin. He says that the test should never have been approved by the US Food and Drug Administration.
PSA testing, according to Ablin, can't detect prostatic cancer and, even worse, can't distinguish aggressive life-threatening cancer from cancer that will never kill those who harbour it. The test "is little better than a coin toss".
The article has made quite a stir in the USA, where the test is widely advocated and is recommended by the American Urological Association. As usual, financial considerations come into this: PSA testing costs at least $3bn a year and the consequent biopsies and prostatectomies, often unnecessary, generate even more.
In Britain we are more conservative: most experts here say that PSA screening of healthy men is not justified. But the UK Prostate Cancer Charity recently lamented the ignorance of British men about the PSA test and said that this was "completely unacceptable". Which is why I resist appeals for support from this organisation.
Yet again we have a discussion about whether screening for cancer, this time of the breast, is necessarily a good thing. Peter Gotzsche, director of the Nordic Cochrane Centre in Copenhagen, has renewed his criticism of screening programmes. Together with Karsten Jorgensen he has reviewed breast cancer trends in the UK, Canada, Australia, Sweden, and Norway. Similar levels of over-diagnosis were found in all the countries.
These researchers say that for every woman whose life is saved by screening, up to 10 will be over-diagnosed and up to 500 will have at least one false alarm, leading to biopsy in half the cases.
This does not of course mean that women should not go forward for screening, but it does mean that the decision not to do so is not irrational. As with the PSA test for prostate cancer, there is a balance to be struck. Yes, the test may show up a cancer that can be treated successfully, but it may also produce a false positive and even when a cancer is found it does not always need to be treated; it may regress spontaneously or may never become aggressive in the course of the patient's natural life span.
As so often in medicine, uncertainty about the best course to follow exists. Women who are perplexed about whether to go for screening should discuss it with their GP. Gilbert Welch, a professor of medicine at the Dartmouth Institute for Health Policy in the USA, is quoted in the Independent as saying: 'Mammography is one of medicine's close calls - a delicate balance between benefits and harms.'
The current issue of The New England Journal of Medicine has several articles about PSA screening for prostate cancer. There is a lot of ill-informed advocacy in the media, including the BBC, to try to get everyone to take this test. But the balance of benefit against harm is still unclear, as an editorial in the journal makes clear after reviewing the results of two large surveys in the USA and Europe.
After digesting these reports, where do we stand regarding the PSA controversy? Serial PSA screening has at best a modest effect on prostate-cancer mortality during the first decade of follow-up. This benefit comes at the cost of substantial overdiagnosis and overtreatment. It is important to remember that the key question is not whether PSA screening is effective but whether it does more good than harm. For this reason, comparisons of the ERSPC estimates of the effectiveness of PSA screening with, for example, the similarly modest effectiveness of breast-cancer screening cannot be made without simultaneously appreciating the much higher risks of overdiagnosis and overtreatment associated with PSA screening.
The article concludes that it is more appropriate than ever for decisions about screening in individual cases to be made on the basis of discussion, not blanket recommendation.
I've mentioned PSA (prostate specific antigen) several times in this blog, because I was annoyed with the BBC for indirectly promoting screening for prostate cancer in dramas. It seems the media in Australia are similarly pushing this, according to Minerva in today's BMJ.There has been a huge campaign telling Australian men that they can "save their lives" by measuring their PSA levels and downplaying the risks of surgery. Those who raised concerns were vilified. I wonder what is behind this misrepresentation of the facts?
A letter in the same issue of the BMJ from Gerard Dubois, at the University Hospital of Amiens, says that "screening for prostate cancer in men over 50 is hardly acceptable becuse overdiagnosis is obvious and the impact on mortality remains unproved despite numerous trials in the past 15 years. ... The only demonstrated effect of prostate screening is a 5-10% biopsy rate in the screened population, with a risk of sepsis and haemorrhage. Plus, for those treated, various adverse effects (impotence, incontinence, pain, rectal ulcers, etc.)"
Prof. Nicholas Wald, director of the Wolfson Institute of Preventive Medicine, says that the whole-body screening services now being offered by various commercial enterprises are a bad idea. Writing in the Journal of Medical Screening he points out that screening of this sort misses most cases of the diseases it is supposed to detect. It also produces plenty of false positives which then require further investigation to rule them out. On top of all this it provides a lot of radiation. We are going to have more and more bogus medicine of this kind, including genetic screening, which is also being touted now.
The BBC programme Check-up today was on prostate problems, especially cancer. I was glad to hear that the medical expert taking part firmly pointed out the short-comings of PSA (prostate-specific-antigen) as a screening test, something I've written about here more than once in the past. The whole programme was a welcome antidote to some of the misinformed propaganda that has been put out, including by the BBC.
Jeremy Laurance has a piece in today's "Independent" questioning the value of medical checkups. Good for him. He mentions both prostate screening and mammograms, both of which I've blogged about myself.
Whether mammography for women aged between 50 and 69 is a good idea is still not a clear-cut issue. A paper in this weekâ€™s BMJ looks at age-specific outcomes and concludes that the benefits and harms of screening are finely balanced.
The potential harms include anxiety, which may be long-lasting, caused by false positive results and the psychological and physical impact of detection and treatment of disease that would not have caused any problems if left untreated. (Very similar considerations apply to prostate cancer screening for men.)
In essence the decision to be screened is a gamble; there is only a small chance of benefit but the stakes are high. Some women will choose the gamble even though they may experience anxiety, inconvenience, and physical adverse effects; other women will not.
Reference: Barrat A et al., Model of screening mammography: information to support informed choices. BMJ 2005;330:936-8.
In Sunday's episode of Down To Earth on BBC1, the central character, Tony, went to get the results of his prostate biopsy. He was having this because his GP had done a test for PSA (prostate specific antigen) and found it to be raised. The biopsy result, predictably, was normal: Tony didn't have cancer. He therefore told the consultant that he thought he'd wasted his time by having the test. "Not so," the consultant replied; "it's a good thing to do and if more men had it we would catch their cancers earlier and be able to cure them"
In other words, the programme was endorsing the value of prostate cancer screening for everyone. What the GP didnâ€™t tell Tony was that there is a large overlap between normal and abnormal levels of PSA, and what the consultant didn't say is that many men with prostate cancer will never have any problems from it and will die of something else; moreover, at present there is no consensus about the best way to treat this cancer once it has been diagnosed or even if it should be treated at all rather than watched. The value of screening for prostate cancer with the current available methods is therefore uncertain at best. It seems irresponsible to put out advocacy for screening in a programme of this kind.
Here are some references to discussions of this question:
1. Prostate cancer intervention.
2. Prostate test "of little value"
3. Trials of treatment needed first.