Bowel (colorectal) cancer: symptoms, screening and treatment review

Bowel cancer starts in the large bowel, and screening can find it early. Some people feel well in the early stages, so it helps to know the signs, the risk factors and the tests. This article draws on information from the World Health Organization (WHO), the NHS and the US Centers for Disease Control and Prevention (CDC).

1. Introduction

Bowel cancer, also called colorectal cancer, is cancer found anywhere in the large bowel, which includes the colon (the large intestine) and the rectum (the passage that connects the colon to the anus) ^{[1, 6]}. The WHO says it is the third most common cancer in the world, about 10% of all cancer cases, and the second leading cause of cancer deaths. It mainly affects people aged 50 and over, although rates are rising among adults aged 30 to 50 in some countries ^[1].

The CDC explains that it starts when cells in the colon or rectum grow out of control, and that some abnormal growths called polyps may turn into cancer over time ^[6].

2. Causes and risk factors

It is not always known what causes bowel cancer. The NHS says it may be linked to changes in genes, lifestyle and environment ^[3]. You may be at higher risk if you ^[3]:

• are over 50
• smoke
• are overweight
• have a close relative who has had bowel cancer
• have inflammatory bowel disease, such as Crohn's disease or ulcerative colitis
• have bowel polyps
• have an inherited condition such as Lynch syndrome or familial adenomatous polyposis (FAP)

The WHO also lists eating a lot of red and processed meat and few fruits and vegetables, being physically inactive, and drinking alcohol. Having had colorectal cancer or certain polyps before also raises the risk ^[1].

3. Signs and symptoms

The WHO notes that many people have no symptoms or only mild ones early on ^[1]. The NHS lists these possible symptoms ^[2]:

• Unusual changes in your stool, such as softer stool, diarrhoea or constipation
• Needing to go to the toilet more or less often than usual
• Blood in the stool, which may look red or black, or bleeding from the bottom
• Often feeling the urge to go, even just after using the toilet
• Tummy pain, a lump in the tummy or bloating
• Losing weight without trying
• Feeling very tired or short of breath, which can be signs of anaemia (a low level of red blood cells or iron, which the WHO links to long-term bleeding from the cancer ^[1])

Many of these symptoms have other causes, so having one does not mean you have cancer. Still, getting checked is important because early detection makes treatment easier ^[2].

4. Diagnosis and tests

At a first appointment, a doctor may ask about your symptoms and family history, examine your tummy, carry out a rectal examination, or ask for a stool sample, a home test kit called FIT (which looks for hidden blood in stool) or a blood test. You can ask for a male or female doctor or nurse for the rectal examination and can have someone else in the room ^[2].

The main test is a colonoscopy. A thin, flexible tube with a camera examines the inside of the bowel. You are offered sedation and painkillers, and a small tissue sample called a biopsy may be taken ^[4]. The WHO also lists ultrasound, CT and MRI scans as imaging tests that may be used ^[1].

If cancer is found, further tests such as CT, MRI or PET scans, blood tests and genetic testing show how far it has spread and whether certain gene changes are involved. Your team uses the results to decide on treatment ^[4].

5. Treatment and management

The NHS explains that the plan depends on the size of the tumour, whether it is in the colon, the rectum or both, whether it has spread, certain gene changes, and your age and general health. Treatments are often combined ^[5]. The options include ^[5]:

• Surgery to remove the cancer, sometimes with part or all of the nearby bowel.
• Chemotherapy, which uses medicines to destroy cancer cells. It may be given before surgery to shrink a tumour, after surgery to lower the chance of the cancer coming back, or when the cancer has spread.
• Radiotherapy, which uses targeted beams of radiation, mentioned for rectal cancer and for cancer that has spread.
• Targeted medicines and immunotherapy, sometimes used for advanced bowel cancer.
• Palliative care, which helps manage symptoms when the cancer cannot be removed.

Surgery may involve a stoma, which is an opening in the tummy wall through which waste leaves the body into a bag. It may be temporary or permanent ^[5]. Your specialist team will explain the side effects of each option and help you manage them ^[5]. The WHO stresses that follow-up over the long term is essential after treatment for early-stage disease ^[1].

6. Prevention and screening

The NHS says you cannot always prevent bowel cancer, but you can lower your chance by ^[3]:

• eating a healthy diet with at least five portions of fruit and vegetables a day
• staying active and exercising regularly
• losing weight if you are overweight
• stopping smoking
• drinking less alcohol
• eating less red and processed meat

Screening checks people who have no symptoms. The WHO says that where organised screening exists, regular screening is the most effective way to find cancer early and to find and remove precancerous growths, and that it reduces both new cases and deaths ^[1]. The CDC advises adults aged 45 and over to talk with their doctor about screening ^[6]. People with a family history or an inherited condition may benefit from genetic counselling and a personal screening plan ^[1].

7. When to see a doctor

See a doctor if you have any symptom of bowel cancer ^[2]. Ask for an urgent appointment if your stool is black or dark red, or you have bloody diarrhoea ^[2].

Get emergency help if you are bleeding from the bottom and it will not stop, or if there is a lot of blood or large blood clots when you pass stool. Do not drive yourself ^[2].

In an emergency, call your local emergency number (112 in India, 911 in the United States).

8. Conclusion

Bowel cancer is common but can often be found early, and screening can even find polyps before they turn into cancer. Knowing the symptoms, keeping a healthy lifestyle and speaking to your doctor about screening are practical steps. If you are diagnosed, a team of specialists plans surgery, medicines or radiotherapy with you, and support is available throughout. Tell your doctor about every treatment you use.