50 Is the Number for a Bowel Cancer Check. For Some Men, the Time Comes Sooner.

Colorectal cancers tend to develop through the gradual accumulation of damage to the DNA of the cells lining the colon. This so-called multi-hit hypothesis means the cells usually need to acquire enough damage before a cancer develops. In most people that takes time — which is why we tend to see the incidence of colorectal cancer start to rise from around age 50.

The caveat is that not all “insults” to the colon are the same; some are more carcinogenic than others, and some factors cause more DNA damage than others. So at a population level, when we look at averages and statistics, 50 makes sense from a public health perspective. But public health data does not always translate into the best, most informed decision for any one individual.

The colon is pliable and expansile. For a lesion to actually cause symptoms it usually has to be quite large — which means a larger, more advanced tumour. So if we wait until symptoms appear, we are usually dealing with a bigger, later-stage cancer and poorer outcomes.

There has been a worldwide trend of younger patients developing colorectal cancer. This may reflect changes in environment and diet that expose the colon to carcinogenic substances earlier in life — perhaps more processed food, or changes in the gut microbiome.

It means we should not hold rigidly to a single age to start screening, but allow some flexibility. The data behind any guideline is historical, so guidelines will always lag the real change in epidemiology. And remember: guidelines apply to people with no symptoms. Anyone with symptoms, at any age, already falls outside them.

For people without symptoms, certain conditions warrant an earlier screening date: a family history of colorectal cancer in a close relative (especially if diagnosed young), a history of inflammatory bowel disease, or a history of an inherited bowel condition.

On family history, the advice depends on the age your relative was diagnosed. In general, if a close relative developed colorectal cancer at 60 or younger, you should have a colonoscopy ten years before their age at diagnosis. If they were diagnosed after 60, the age-50 recommendation still stands. The practical challenge is that most people simply don’t remember the age at which their relative’s cancer was found.

Anyone with bowel symptoms shouldn’t wait until 50 either. Bowel symptoms are common and usually benign, but they are also the same symptoms a tumour can cause. Constipation or difficulty passing motion may be an obstructing tumour, or simply too little fibre. Blood in the toilet bowl may be haemorrhoids — or a tumour.

Once there are symptoms, the age-50 recommendation no longer applies, and you should be assessed on the symptoms themselves. The doctor’s job is to judge how likely those symptoms are to be a colonic tumour rather than a benign cause. In most cases it is difficult to rule out a tumour from the symptoms alone, so further investigation is often needed.

Essentially any colonic symptom — constipation, abdominal bloating, bleeding — is worth a review, and anything recurrent or persistent should prompt a visit to a doctor. There is, unfortunately, no neat rule about how often or how long symptoms must last before they point to something serious rather than something benign.

So why bother, if most turn out to be benign? Because a proper assessment weighs the risk of missing something serious against the inconvenience — and small risks — of further investigation. As a rule, the first far outweighs the second.

There are two main approaches, and they are not interchangeable.

The first is a stool test you do at home — the faecal immunochemical test, or FIT. It checks for tiny amounts of blood you cannot see, takes only a few minutes, needs no special preparation, and for average-risk men is repeated once a year. A positive result does not mean cancer; it means a colonoscopy is needed to look properly.

The second is a colonoscopy, where a doctor examines the bowel directly with a thin, flexible camera while you are sedated. It is the most thorough option, with a real advantage: any polyps found can usually be removed in the same sitting, before they ever have the chance to turn into cancer. Most men say the preparation the day before is the least pleasant part, and that the procedure itself passes quickly.

The reassuring part for average-risk men: if your colonoscopy is clear, you generally won’t need another for a long time — typically once every five to ten years rather than annually, provided no new symptoms appear in between. One thorough check can buy you the better part of a decade of peace of mind.