Bowel Cancer Overview

Introduction

Bowel cancer (also referred to as colorectal cancer), is a form of cancer that affects the colon and rectum, which are parts of the large intestine. It typically begins as a growth or polyp on the inner lining of the colon or rectum; over time, these polyps can become cancerous. Bowel cancer is the third most common type of cancer worldwide and a leading cause of cancer-related deaths.

Causes and risk factors 

The exact cause of bowel cancer is not fully understood, but several factors have been identified as contributing to its development. These include:

Genetic factors 

Certain inherited genetic mutations (a change in a DNA sequence), such as those associated with familial adenomatous polyposis (FAP) and hereditary non-polyposis colorectal cancer (HNPCC), can significantly increase the risk of developing bowel cancer.¹

Age 

The risk of bowel cancer rises with age, with the majority of cases occurring among people over the age of 50.²

Diet and lifestyle factors 

• A diet that is high in red and processed meats, low in fibre, and excessive alcohol consumption has been linked to an increased risk of bowel cancer³ 
• In addition, obesity, physical inactivity and smoking are associated with higher risk

Inflammatory bowel diseases 

Individuals with chronic inflammatory bowel diseases, such as ulcerative colitis and Crohn's disease, have an increased risk of developing bowel cancer.⁴

Symptoms

In the early stages, bowel cancer may not exhibit any noticeable symptoms. However, as the disease progresses, the following symptoms may be experienced:

• Changes in bowel habits:
  • Persistent diarrhoea 
  • Constipation 
  • A feeling of incomplete bowel movement
• Rectal bleeding or blood in the stool
• Abdominal pain or discomfort
• Unexplained weight loss
• Fatigue or weakness
• Anaemia (low red blood cell count)

Diagnosis

 Diagnosing bowel cancer typically involves a combination of the following tests and procedures:

Faecal immunochemical test (FIT)

• A faecal immunochemical test (FIT) looks for the presence of blood in stool, which can be an early indicator of bowel cancer or other gastrointestinal conditions 
• They are often screening tests for individuals at an average risk of developing bowel cancer⁵

Colonoscopy 

• Colonoscopy is widely regarded as the gold standard for diagnosing bowel cancer 
• During this procedure, a flexible tube with a camera (colonoscope) is inserted through the rectum to examine the entire colon and rectum 
• If any abnormal growths or polyps are found, they can be removed or biopsied (examined under a microscope) for further analysis⁶

Biopsy 

• A biopsy may be performed if any suspicious growths or polyps are found during a colonoscopy or other imaging tests 
• The tissue sample is then examined under a microscope to determine if it is cancerous or precancerous⁷

Imaging tests 

Techniques such as computed tomography (CT) scans, magnetic resonance imaging (MRI), and positron emission tomography (PET) scans may be used to assess the extent of the cancer and determine if it has spread elsewhere in the body.

CT colonography (virtual colonoscopy) 

• CT colonography is a non-invasive imaging test that uses computed tomography (CT) scans to create detailed images of the colon and rectum 
• It can detect polyps and other abnormalities but cannot remove them⁸

Treatment and management

Surgery 

• Surgical removal of the cancerous tumour and surrounding tissue is often the primary treatment for early-stage bowel cancer 
• Depending on the location and extent of the tumour, different surgical procedures may be performed, such as a colectomy (removal of part of the colon) or a proctocolectomy (removal of the rectum and partial removal of the colon)⁹

Chemotherapy 

• Chemotherapy drugs are used to kill cancer cells and may be administered before or after surgery, or in combination with radiation therapy 
• Chemotherapy can be given intravenously or orally¹⁰

Radiation therapy 

• Radiation therapy uses high-energy X-rays to destroy cancer cells and shrink tumours 
• It can be used before surgery to reduce the tumour size or after surgery to eradicate any remaining cancer cells¹¹

Targeted therapy 

Targeted therapies are drugs that specifically target and interfere with the growth and spread of cancer cells by targeting specific molecules or pathways involved in cancer cell growth and survival.¹²

Immunotherapy 

• Immunotherapy is a treatment approach that harnesses the body's immune system to recognise and attack cancer cells 
• It may be used in combination with other treatments or as a standalone therapy for certain types of bowel cancer¹³

Prevention and screening

While some risk factors for bowel cancer, such as age and genetics, are not modifiable, several strategies can be implemented to reduce the risk and promote early detection:

Regular screening 

Regular screening tests, such as a faecal immunochemical test (FIT) or colonoscopy, can detect bowel cancer early when it is more treatable.

Healthy diet and lifestyle 

Maintaining a healthy diet that is rich in fruits, vegetables, and whole grains, engaging in regular physical activity, and avoiding both excessive alcohol consumption and smoking can help minimise the risk of bowel cancer.

Aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) 

• Some studies have suggested that regular use of aspirin or other NSAIDs may reduce the risk of developing bowel cancer¹⁴
• However, use of aspirin should be discussed with a healthcare provider due to potential side effects (e.g. stomach ulcers)

Genetic counselling and testing

For individuals with a strong family history of bowel cancer or known genetic mutations, genetic counselling, and testing may be recommended to assess their risk and determine appropriate screening and prevention strategies.

FAQs

What’s the difference between colon cancer and rectal cancer? 

• Colon cancer and rectal cancer are often referred to as bowel cancer or colorectal cancer 
• The main difference is the location of the cancer 
• Colon cancer occurs in the colon (the first 5-6 feet of the large intestine), while rectal cancer occurs in the rectum (the last 6-12 inches of the large intestine)

When should I start getting screened for bowel cancer? 

• Most guidelines recommend that individuals at average risk for bowel cancer begin regular screening at age 50 
• However, those with a family history or other risk factors may need to start screening earlier 
• It is essential to discuss screening recommendations with a healthcare provider

Summary

• Bowel cancer, also known as colorectal cancer, is a type of cancer that affects the colon and rectum, which are parts of the large intestine
• It typically begins as a growth or polyp on the inner lining of the colon or rectum; over time, these polyps can become cancerous
• Bowel cancer is one of the most common types of cancer worldwide, with a higher incidence in developed countries. Risk factors include age, family history, inflammatory bowel diseases, obesity, smoking, excessive alcohol consumption, and a diet high in red and processed meats
• Early detection through screening tests like colonoscopy, a faecal immunochemical test (FIT), and stool DNA test is crucial, as bowel cancer is often asymptomatic in its early stages
• Symptoms may include changes in bowel habits, blood in the stool, abdominal pain, unexplained weight loss, and fatigue
• Treatment options depend on the stage and location of the cancer and may involve surgery, chemotherapy, radiation therapy, targeted therapy, or a combination of these approaches
• Prognosis is generally favourable if the cancer is detected and treated early, but advanced stages have a lower survival rate
• Prevention strategies include maintaining a healthy lifestyle, regular screening, and prompt medical attention for any concerning symptoms