Anyone who’s romped through to the closing pages of Betrayed by Nature will (we hope) be grateful to have come upon a succinct summary of the pros and cons of screening, particularly for breast cancer. In the UK screening (i.e. mammography: see Breast Cancer – Seeing Red, Jan 2012 for explanation) is offered to women aged 50-70 every three years – so clearly ‘we’ think it’s a Good Thing. However, the waters are less than crystal clear because several studies have concluded that as many as one in three cancers identified by mammography would not cause any symptoms during the lifetime of the patient – and suggested that countries should spend the money on other things. The simple message you were relieved to read in BbN was that, whilst the matter is controversial, if you are offered screening, accept – whilst being aware that a ‘positive’ is not always a signal for intervention (by surgery and drugs) and that in deciding on a course of action you should be guided by the best advice your clinicians can give.
Trying to bring resolution to this complicated and important matter, yet another ‘official review’ has just appeared in The Lancet – predictably accompanied by some absurdly inflammatory press headlines. So, ignoring them and your groans – and because it is important – can we recap the key points and reassess the clear BbN message? Of course we can – that’s what we do in “Cancer for All.”
Any type of screen for signs of cancer has two problems for those on the receiving end. First it will miss some and second it will sometimes pick up things that, although abnormal, will never become life-threatening. This latest report estimates that screening reduces the relative risk by 20%, i.e. prevents one breast cancer death for every 235 women invited for screening, equivalent to 43 preventions per 10,000 women aged 50 who are screened over the next 20 years. The downside is that about 130 women in every 10,000 are what is called ‘overdiagnosed’: they receive treatment for something that could simply be left alone. Of course that’s highly undesirable as well as stressful and unpleasant for the patient. However, it is rarely fatal – and at least carries an element of reassurance that they won’t develop breast cancer.
So, in the light of the newest info, is BbN’s take in need of modification? No, it’s just fine. What a relief!! But just bear a couple of other points in mind: the sensitivity of screening is gradually improving and dramatic improvements in analysing tumours at the molecular level mean that ‘overdiagnosing’ will decline. As we’ve pointed out, the system isn’t perfect – then neither are we or we wouldn’t get cancers – but it’s heading in the right direction.
Independent UK Panel on Breast Cancer Screening. The benefits and harms of breast cancer screening: an independent review. The Lancet October 2012.