01.12.12
Screening: hit or miss?
Source: National Health Executive Nov/Dec 2012
Professor Simon Thompson, director of research in biostatistics at the University of Cambridge, speaks to NHE about the results of the independent breast cancer screening review and its implications for the NHS.
The independent breast cancer screening review published its conclusions on October 30, highlighting that the prevalence of overdiagnosis was higher than previously thought, despite screening preventing around 1,300 deaths from the disease each year.
A panel of experts was commissioned by Cancer Research UK and the Department of Health to conduct a study into the impact of breast screening programmes in the UK; looking into whether these effectively identify tumours early, thus improving the chances of good treatment and survival, and how many women are treated unnecessarily for lumps which would not have posed damage to the woman’s health in her lifetime.
NHE talked to Professor Simon Thompson, director of research in biostatistics at the University of Cambridge and a member of the panel that produced the report, about the controversy which surrounded screening programmes and the move to improve the information available to the public.
Balancing risks and benefits
He said: “It is important to present to women the balance of the benefi t in terms of a decreased risk of dying from breast cancer on the one side and the risk of overdiagnosis on the other. This information needs to be made very clear to women who are invited for screening.
“I think it’s quite difficult to predict what will happen and how women will react. Some of the evidence we’ve had so far is that many women would still want to attend screening, but we don’t know how it will play out in the future.”
The Government has announced that the leafl ets sent out to invite women aged between 50 and 70 to screening will be revised to include the new statistics about the possibility of misdiagnosis, as well as the benefi ts screening can bring.
Professor Thompson said: “There will be new leafl ets with updated information that I think better refl ects the balance of the advantages and the disadvantages.”
Work is also ongoing to refi ne the screening process so doctors are better able to identify which tumours will go on to become dangerous ahead of treatment. Professor Thompson highlighted this as a “key issue”, and the panel has recommended future research in this area.
He said: “If we could tell, when a cancer is diagnosed by screening, whether it was one that was going to go on and be a potential cause of death [or] whether it would actually really not be an important issue, that would be a great advance and would also clearly ameliorate this problem of over-diagnosis through screening. That is a priority and indeed research is going on.”
Side effects
The issue of screening is still fairly contentious, and some argue that such programmes do more harm than good, subjecting thousands of women to painful treatment that they do not need, whilst failing to identify those whose tumours will present serious problems to their health.
Evidence on the issue is mixed, and Professor Thompson stated that he hoped this latest research would clarify the matter further; that overdiagnosis is an unfortunate side effect of a programme that saves a lot of lives.
In all health practice there will be a degree of uncertainty regarding how an individual patient will respond to treatment, and this is exacerbated in cancer where we are still learning about the behaviour of the disease. For some the chance that they could undergo unnecessary treatment is a small price to pay to ensure they remain healthy and safe – for others it is inviting discomfort and added expense on the NHS for no reason.
Out of date
Some have criticised the reliability of the panel’s conclusions, since some of the evidence used in the review is several years old.
Professor Thompson admitted that “they do have a disadvantage in this case that they were conducted some time ago,” but added: “We did consider other forms of evidence as well. We considered more recent observational studies and still thought that the best evidence we could use comes from the trials, and that’s what we based our estimates on.”
Screening has changed considerably since then, with mammography’s ability to detect deepseated tumours improving over the past 20 years, and the subsequent treatment of cancers also undergoing change. Professor Thompson concluded: “We heard from a number of witnesses as part of our review, as to how they thought this would influence the benefits of mammography. I think the consensus was that they thought the benefits seen in the trial should roughly apply to current-day screening.
“I hope that as this comes as a report from an independent panel, the new level of information will give at least some greater clarity, both in terms of policy-making but also for individual women.”