The prostate-specific antigen (PSA) is an enzyme produced by cells in the prostate. One of its roles is to break down the main protein component of semen, making it more liquid after ejaculation.

In prostate cancer, prostate cells grow into a tumour. To simplify, more prostate cells mean more PSA. Therefore, one way to detect possible prostate cancer is to test for circulating levels of PSA in the blood, with higher levels correlating with an increased risk of cancer. The PSA test can be followed up with other tests such as an MRI scan or a biopsy. (The older approach of a “finger up the bum” is no longer considered useful by experts, because it has little diagnostic value and contributes to stigma around prostate cancer.)

Given that prostate cancer is the second-leading cause of cancer in men, it might seem obvious to use the PSA test for everyone at risk: doctors could then identify the cancers early and save lives.

Anyone with a prostate can get prostate cancer: that means cis men, trans women and other gender identities. However, currently in Britain only those aged over 50 can request the test, and are not advised to by the NHS.

Chris Hoy, who received a terminal prostate cancer diagnosis around two years ago, has used his story to call on the NHS to bring the age down and encourage more testing. “To me it seems a no-brainer,” he said in November 2024. “Why would they not reduce the age? Bring the age down and allow more men to go in and get a blood test.” In response, Wes Streeting asked the NHS to review its advice on testing.

Last week, the UK’s National Screening Committee published the result of that review. But contrary to the hopes of Hoy and many campaigners including Stephen Fry, David Cameron and Rishi Sunak, its draft recommendation upholds the status quo. The committee has advised against changing the age guidance and against recommending screening for all men in a national programme (with a few rare exceptions for men at increased risk).

In response to the decision Hoy said he was saddened, because he knew that by sharing his story “many, many lives have been saved” because more men have got tested.

This is true. But the uncomfortable fact is that also means that many have suffered harms they wouldn’t have suffered otherwise. This is not a criticism of Hoy, but a necessary part of the conversation around the realities of screening.

Figures from Cancer Research UK calculate that if 1,000 people aged 50-60 are screened with the PSA test, around 100 will test positive and go on to have further follow-up tests.

Most of them won’t have prostate cancer on those tests, and eventually only 28 will be diagnosed.

Even the majority of these people will not have their lives saved – their prostate cancer was never going to kill them, simply grow harmlessly.

But many of them will still have treatment including surgery and radiotherapy to remove it, which can cause incontinence and impotence. The upshot is that screening will save up to two lives, at the cost of around 12 people receiving unnecessary treatment with serious downsides. The committee’s interpretation of the statistics is that screening will lead to harms that aren’t justified by the number of lives it saves.

This conclusion violates our intuition that prevention is better than cure. But screening measures like the PSA test are not really prevention.

They do not stop disease from happening, but merely identify it. That has repercussions, almost inevitably leading to distress and further healthcare. According to Mike Richards, the chair of the screening committee, for every 700 people whose lives were saved by screening, 7,000 would be left with permanent health issues from unnecessary treatment.

Richards himself had prostate cancer diagnosed by a PSA test after he developed symptoms, but stands by the argument that screening anyone simply because they have a prostate is normally a bad idea, unless they have symptoms.

One difficult area that remains unclear is the evidence surrounding screening in apparently higher-risk groups such as black people. If rates of prostate cancer are high enough and cause enough illness and death, the cost-benefit analysis might change.

The lack of evidence to support this recommendation is due to the failure of medicine to involve black people in previous trials. It’s an urgent matter, and one that new trials will hopefully resolve within two years.

Not all cancer has to be treated. Cancer just means an abnormal cell growth with the potential to spread elsewhere; not all cancers are alike, and not all are fatal. Most people who develop prostate cancer won’t die from it: they will have a lump of cells in their prostate in old age, but it won’t be what kills them. Compared to the effects of cancer treatment, the symptoms will be minimal.

Unfortunately the success of cancer awareness means that the word “cancer” remains terrifying. For people living with a cancer diagnosis, it can be hard to resist treatment.

That’s where the recommendation to avoid testing comes from. Here, better advice about the risks of cancer treatment could preserve many people’s quality of life.

Treatments with fewer side effects would also reduce the damaging consequences of diagnosis.

But there are nearly always going to be intrinsic harms to many medical treatments that are almost impossible to avoid.

It’s important to consider both sides of screening, and disingenuous for those with power to present only one side of the story. The emotive power of cancer can also be a powerful pressure point in a PR machine.

Rishi Sunak led a government that eroded public health. But he is now an ambassador for Prostate Cancer Research. Earlier this year he filmed himself getting a PSA test and encouraging others to do the same. It’s unclear how: he’s only 45, and under government recommendations he isn’t entitled to get one on the NHS.

In his video, he mentions nothing about the harms of treatment, simply repeating the mantra that “early detection really saves lives.” Health is not apolitical.