1 July 2026

I thought I might be saving a patient’s life. What if the opposite were true?

Every drug, operation, test or other intervention carries a risk of harm as well as good

I received a letter from the British Columbia Colon Screening Programme (BCCSP) recently. Like the NHS in the UK, this programme recommends faecal immunochemical tests (Fit) – stool samples that check for microscopic traces of blood – every two years to screen 50- to 75-year-olds for bowel cancer. They’d been trying without success to get feedback from one of my patients who had been referred for a colonoscopy following a positive Fit– could I give them information instead? I knew why they’d heard nothing back. I went into David’s records to get the details for my reply.

There was the entry in October last year, when David had joined my list, aged 72, after his former GP had retired. We’d talked about his previous heart valve replacement, atrial fibrillation and mild heart failure, reviewed his symptoms (negligible) and medication. Then I’d turned the conversation to preventative matters. No, he told me, he hadn’t had a Fit for at least ten years. I offered to arrange one. He’d be eligible for a couple more before passing the age cut-off.

Then there was the positive result, the colonoscopy referral, and the news of the cancer growing unsuspected in David’s gut. I looked over the subsequent clinic notes planning the operation to remove the growth, and the factors that suggested there was no sign it had spread.

I remember thinking at the time, as David did, how fortunate he had been. Thanks to a simple test, a cancer had been discovered at a stage where there were good prospects of cure. The surgeon hoped to excise it using keyhole techniques but warned that conversion to a more extensive open procedure might be required. David told me he was braced for either eventuality and was keen to get the tumour gone.

It was the last time we spoke. Open surgery had proved necessary but had gone well. Then the ileus had set in – a recognised complication where the bowel becomes temporarily paralysed in reaction to the operative trauma. That had led to the aspiration of vomit into the lungs, and a cardiac arrest. They’d managed to bring David back and get him on to ICU, only for his heart to stop again, this time irreversibly.

It was salutary, reading those records again, alone in the quiet of my consulting room. How that innocuous conversation last October was the start of a chain of events that within a few months would end David’s life. What if I hadn’t mentioned the Fit? What if he’d told me he hadn’t bothered with them for the past ten years and wasn’t about to start doing so now? How much of his agreement to perform one was about not wanting to offend this new doctor from England, to whom he was grateful for taking him on?

Doctors know well that every drug, operation, test or other intervention carries a risk of harm as well as good – something that gets hugely downplayed in popular discourse. Was the information I had given David balanced enough for his screening decision? These days, I counsel female patients at standard risk that mammographic screening, while marginally reducing breast cancer deaths, doesn’t save lives. As many patients die from complications of treatment – magnified by the fact that screening detects many tumours that would never cause disease – as have their prognosis improved. Researching the latest literature, I discovered what I didn’t know last October, and is still not being discussed: the same is true of Fit. The trials that underpin these screening programmes are geared to delineate the positives, but poor at capturing data about harm.

How long might it have taken David’s cancer to announce itself had he not undertaken that Fit? Would it ever have done so? The perception of screening as an unalloyed good is bedevilled not just by the partiality of the scientific data, but also by the stories we get to hear. Those who survive cancer detection and treatment understandably proclaim what feels like their great fortune. But the countervailing voices, of people like David who never lived to tell their tale, have long since fallen silent.

[Further reading: The Degradation of Independence]