Bowel cancer

The large bowel is the last stretch of the digestive tract: the colon, where water is drawn back out of the food mush, and the rectum, where stool is formed and held. A tumour can grow anywhere along it, and where it sits determines how it gives itself away. It is one of the commonest cancers in adults, and one of the very few that can genuinely be prevented, because almost always it takes years to grow out of a harmless polyp. Found early, it is curable.

How a polyp turns into a tumour

Polyps, small outgrowths of the lining, appear on the inner surface of the bowel from time to time. Most of them stay harmless, but in some the cells accumulate faults, and after eight to ten years the polyp can become a malignant tumour.

Two conclusions follow. The bad one: throughout all that time the person feels nothing, because a polyp does not hurt. The good one: years separate "there is now something to remove" from "it is too late", and a polyp found in that window is snared off during the examination itself, so the tumour simply never happens.

Signs you should not put down to piles

An early tumour causes no symptoms. When they do appear, they are usually these:

• your bowel habit has changed and has not gone back: looser stool, or on the contrary constipation, and going more often or less often than is normal for you;
• blood in the stool, bright red, dark, or as a black tarry motion;
• a feeling of not having emptied fully, and the urge returning soon after going;
• pain or bloating in the abdomen, particularly linked to eating;
• a lump you can feel in the abdomen;
• weight loss without dieting or trying;
• weakness, breathlessness on ordinary exertion and pallor, which are signs of anaemia from unnoticed blood loss.

A separate word about blood. Piles are not an alibi: huge numbers of people have them, and they say nothing about what is happening higher up. The most expensive mistake sounds like this: "there has been blood before, it is my piles." If the bleeding has changed in character, or the stool has changed as well, the bowel needs looking at.

The second underrated sign is iron deficiency anaemia in a man or in a woman past the menopause. If there is no obvious source of blood loss, the bowel must be investigated even when nothing hurts.

When to book an appointment and when to go straight in

Book an appointment if any of those signs lasts three weeks or longer. There is nothing to be embarrassed about: for a doctor, conversations about bowel habits are routine.

Emergency care is needed straight away if:

• bleeding from the back passage is heavy and will not stop, the water in the toilet turns red, or clots are coming away;
• severe abdominal pain has come on with vomiting, the abdomen is swollen, and no wind or stool is passing, which is how an obstruction shows itself;
• the abdomen has become hard and painful at the lightest touch and a fever has developed.

Do not drive in that state: ask someone to take you or call an ambulance. Bring a list of the medicines you take, particularly any blood thinners.

What raises the risk and what you can change

There is no single cause: inheritance, age and habits all add up. The risk is higher if:

• you are over fifty, although the disease has moved younger and past forty it can no longer be treated as somebody else's problem;
• a parent, brother, sister or child has had bowel cancer or polyps;
• there is Lynch syndrome or familial adenomatous polyposis in the family, uncommon inherited conditions in which tumours appear early and surveillance starts in young adulthood;
• you have had ulcerative colitis or Crohn's disease for many years;
• polyps have been found in you before;
• you smoke or drink alcohol regularly;
• there is excess weight, little movement, plenty of red and processed meat and little fibre in the diet.

The first points cannot be changed, but they are exactly what decides from what age and how often you should be checked, so do tell your doctor about cancer in the family. The rest is in your hands: stopping smoking, moderation with alcohol, vegetables, fruit and wholegrains instead of processed meats, movement and a sensible weight. None of it guarantees anything, but it lowers the risk appreciably.

Checking when nothing is wrong

Screening, that is testing people who have no complaints, works better in bowel cancer than almost anywhere else in medicine, because removing a polyp prevents the disease itself.

There are two tools. The faecal immunochemical test for hidden blood is done at home: a small sample is collected with a stick and posted to a laboratory. It does not make a diagnosis, it selects the people whose bowel needs looking at; a positive result more often has a harmless explanation, but it must always be followed up. Colonoscopy, an inspection of the bowel from inside with a flexible tube and a camera, is examination and treatment in one, because any polyp found is removed on the spot.

The starting age and the interval differ between countries; programmes usually begin between forty-five and fifty, and earlier and straight to colonoscopy where the family history is loaded. Check the rules where you live, and do not leave a screening invitation lying in the pile.

How the diagnosis is confirmed

The doctor will ask about your symptoms, your past illnesses and your relatives, feel the abdomen and most likely carry out a rectal examination, a short procedure that picks up a good share of tumours in the lower part. You may ask for a clinician of a particular sex and for someone to be in the room with you.

Next come the stool test for hidden blood, a blood test, and, where there is suspicion, colonoscopy. It is done with pain relief and sedation and most people do not remember it; the unpleasant part is the preparation the day before, not the procedure. A suspicious area is sent for examination, and that is what gives the final answer.

If a tumour is confirmed, a computed tomography scan follows, magnetic resonance imaging for rectal cancer, sometimes a positron emission scan, plus study of the genetic features of the tumour: all of it serves to establish the stage and choose treatment. Being referred for further tests does not in itself mean there is cancer; in most people referred, none is found.

How it is treated

Treatment is fitted to the case: the size and site of the tumour, spread beyond the bowel, genetic features, age and other illnesses. It is usually a combination of methods.

• Surgery. The main approach while the tumour has not left the bowel. The affected segment is removed along with its lymph nodes and the ends are joined. Sometimes, while healing takes place, a stoma is formed, an opening on the abdomen for bowel contents; more often it is temporary and is closed a few months later.
• Chemotherapy. Before or after surgery, to shrink the tumour or reduce the chance of it coming back, and also in advanced disease.
• Radiotherapy. Mainly in rectal cancer, often together with chemotherapy before an operation.
• Targeted drugs and immunotherapy. These act on features of the tumour cells themselves and are used in advanced disease when testing shows the right changes.

If the tumour is far advanced and cure is not possible, treatment does not stop: its aim becomes holding back growth, relieving pain and keeping ordinary life going as long as possible. That is the work of the palliative care team, and bringing them in early is worth doing, because they make life easier both for the person and for those close to them.

Online consultation

In an online consultation the doctor will go through your symptoms and work out which of them call for the bowel to be investigated, explain the test results you already have, help you decide whether it is time for a colonoscopy, review your family history and advise from what age you personally should start being checked.

This material is for information only and does not replace medical advice.