The cost of caution: rethinking how we make cancer screening decisions

17 September 2026

Screening involves healthy people, limited healthcare resources, uncertain evidence and difficult trade-offs between benefits and harms.

In a recent eClinicalMedicine Viewpoint, Professor Peter Sasieni, joint lead of the Centre for Cancer Screening, Prevention, and Early Diagnosis at Queen Mary University of London and Professor Stephen John, the Hatton Professor in the Philosophy of Public Health at the Department of History and Philosophy of Science, University of Cambridge, argue that we need to rethink how cancer screening policy is made. They suggest that an emphasis on evidential certainty can lead to delays, potentially avoidable deaths and widening health inequalities. Screening decisions should involve a broader consideration of ethical, social and political values.

We sat down with Peter to discuss why he believes that doing nothing is itself a decision, and one that can have consequences.

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Jane Rigney: Peter, your recent article in eClinicalMedicine suggests that cancer screening policy is not simply about following the evidence. Critics would argue that the stringent thresholds and long validation processes for screening are there to protect patients. Why are you criticizing what many see as safe, cautious medicine?

Peter Sasieni: Yes, science is fundamental and as a scientist, I always want more data. I always want better evidence. But policymakers don’t live in ivory towers, real-world decisions have to be made while we are still uncertain. We often ignore the deadly cost of doing nothing. Demanding decades of absolute, perfect proof before rolling out a screening programme isn't "caution", it is a bureaucratic delay that is costing thousands of lives in this country.

Jane: That is a stark accusation. Can you give us a concrete example of where this kind of caution has translated into real-world harm?

Peter: Maintaining the status quo is not a neutral act. Policymakers quite rightly worry about making a false-positive decision: introducing a screening programme that ultimately causes more harm than good.

But we also need to think about false-negative decisions: failing to introduce a programme that would have benefited people.

Colorectal cancer screening is a good example. Look at our history: when bowel cancer screening was proven to save lives, it took the NHS 14 years to fully roll it out. Had it been introduced ten years sooner, in just four years, an estimated 20,000 fewer people would have died in England from bowel cancer. Delays cost lives.

Today, the programme prevents around 2,000 colorectal cancer deaths each year in England.

We cannot keep waiting decades for absolute certainty when we can safely estimate the benefits and harms using sophisticated modelling today. We rightly worry about the harms of rushing a decision, but indecision can also cost lives.

Jane: But playing devil's advocate for a moment - aren't you being somewhat irresponsible here? Rushing screening can lead to massive overdiagnosis, unnecessary surgeries, and severe psychological harm for healthy people. Surely, we need to be completely certain?

Peter: Of course, harms and side effects matter, and we must weigh them rigorously. But as an epidemiologist, I look at all the data - and inaction has a heavy death toll. We can model and safely estimate those side effects right now using current datasets. What we shouldn't do is trap ourselves in a 20-year trial while an entire generation of patients dies of preventable cancers.

Don’t get me wrong. I’m a trialist. Half my career has been working on mega trials. But we mustn’t let the perfect be the enemy of the good.

The point we make in the paper is not that we should always act sooner. It is that we should explicitly consider both the harms of acting and the harms of waiting, rather than assuming delay is automatically the safer choice.

Jane: But surely there is a good reason for demanding strong evidence before introducing a screening programme? If we bypass 20-year traditional trials, how do we safely implement these programmes without creating a chaotic rollout? What is the alternative?

Peter: Of course. I am not arguing that evidence doesn't matter. It matters enormously. That said, we must abandon this rigid, binary system where a new test is either fully rolled out nationally or completely rejected. The problem is when we treat evidential certainty as though it is the only consideration. We suggest a middle ground. If evidence is promising but not yet definitive, a carefully designed publicly funded pilot could help generate the additional evidence needed while also allowing people to benefit earlier.

Crucially, we should run these pilots in our most health-deprived regions first. Right now, healthy life expectancy is nearly 20 years shorter in the most deprived areas of England than in the wealthiest.

Jane: Another theme running through the paper is justice. How does caution about screening affect health inequalities?

Peter: This is potentially a very important consequence of delay.

When the NHS delays public screening, the wealthy simply pay to get screened privately.

Look at prostate cancer. Right now, prostate testing is 25% lower in our poorest communities, whilst rates of advanced, incurable prostate cancer are significantly higher there. Targeted pilot programmes fix this injustice while gathering the exact real-world data we need. We've already seen this work, lung cancer screening has been rolled out in the most deprived parts of England first, with excellent results.

Jane: Let's look to the future. We are seeing a surge in artificial intelligence and sophisticated blood tests that can detect multiple types of cancer even before symptoms have developed. How does our current evaluation system handle this new wave of technology?

Peter: It doesn't, and that is why this is urgent. We are on the cusp of an artificial intelligence and genomics revolution - simple blood tests and software that spot multiple cancers early. But AI models and blood tests update every few years. If we insist on evaluating them using traditional clinical trials that take a decade and cost hundreds of millions of pounds, the technology will be obsolete before the trial even finishes. We risk stifling innovation and driving life-saving tech abroad.

What we need is a more adaptive way of generating evidence. For example; carefully designed pilots specifically intended to generate the missing evidence.

That pilot must be monitored against very clear evaluation criteria.

Jane: You’ve argued in your article with Professor Stephen John that choosing whether or not to screen isn't just a clinical decision, but a democratic and ethical one. Why shouldn't we leave these choices entirely to expert committees?

Peter: Deciding whether to offer a type of cancer screening involves profound ethical choices, not just science. Earlier this year, the UK National Screening Committee advised against a prostate screening programme because they decided that the potential risks of incontinence and impotence outweighed the potential benefit of a longer life.

Those harms are real.

But deciding how much weight to put on a possible extension of life compared with those harms is a deeply intimate, personal value judgement.

Different people can reasonably make different choices.

A man who is particularly concerned about the possibility of dying from prostate cancer may be willing to accept a greater risk of treatment-related side effects. Another man may feel very differently.

Experts should summarise the data; but shouldn’t we give adults the balanced facts about these risks and trust them to make their own choices?

Jane: That sounds like a recipe for chaos. Surely we can give people free reign to demand any screening test they might fancy.

Peter: I completely agree. I am not suggesting that all tests are made freely available in the NHS. What I am saying is that when a screening test is shown to have both real benefits and real harms, then it should not be for a group of academic experts to decide. Ideally individuals should be helped to make an informed choice that is right for them. And if that is not possible, screening committees should include a broader group of stakeholders, including citizens and  can be tasked to make that choice on behalf of their peers.

Jane: Critics will inevitably look at the state of the health service and say: "The NHS is on its knees." Changing these evaluation thresholds or expanding screening will overwhelm colonoscopy units and hospital capacity. Isn't this just an impossible resource issue?

Peter: Capacity is a very real issue, but we need an honest, transparent, democratic conversation about competing calls on limited resources. Right now, bowel screening thresholds are quietly altered across England, Scotland, and Wales purely to manage colonoscopy capacity, meaning a stool test result that gets you an urgent investigation in Scotland is marked as 'normal' in Northern Ireland. Let's be transparent about these capacity choices with the public, rather than pretending the science dictates the policy.

Jane: Peter, thank you for your time and for challenging the status quo.

 

Jane Rigney joined the Cancer Prevention Group in 2017 and has over ten years of experience in clinical research, research recruitment, research governance and project management. With a background in public health and health promotion, her interests centre on the delivery of cancer prevention research and ensuring that patient and public involvement meaningfully shapes research.

Jane is also passionate about how research and health information are communicated and shared with the public. She is particularly interested in making evidence accessible, engaging and meaningful, and in bridging the gap between research and the communities it aims to benefit.

 

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