Bowel Cancer: Understanding its Causes, Symptoms and Modern Treatments

Introduction

Bowel cancer—also known as colorectal cancer or colon cancer—is one of the most common types of cancer worldwide. It affects the large bowel, which includes the colon and the rectum, and usually begins as small growths called polyps on the inner lining of the bowel. While not all polyps become cancerous, some can transform over time, making early detection and removal critical.

The Scope of the Disease

Globally, bowel cancer is among the top three most frequently diagnosed cancers and one of the leading causes of cancer-related deaths. In the UK it is the fourth most common cancer and the second biggest cancer killer, with tens of thousands of new cases diagnosed each year. In the United States it ranks third among both men and women. However, survival rates have improved considerably due to better screening, awareness and treatment methods.

How Bowel Cancer Develops

Bowel cancer typically begins when the normal process of cell growth and death in the lining of the bowel becomes disrupted. Instead of dying when they should, cells continue to grow and multiply, leading to the formation of a tumour. Most cases develop from adenomatous polyps, which are benign growths that can accumulate genetic mutations over time. These mutations affect genes that regulate cell division, repair and programmed death, allowing abnormal cells to thrive and invade surrounding tissues.

While the exact cause of these mutations is not always clear, researchers have identified a number of factors that increase a person’s risk.

Risk Factors

  1. Age – The majority of bowel cancer cases occur in people over the age of 50.

  2. Family history and genetics – Having close relatives who have had bowel cancer increases risk, particularly if they were diagnosed before age 50. Certain inherited syndromes, such as Lynch syndrome and familial adenomatous polyposis (FAP) dramatically raise the likelihood of developing the disease.

  3. Diet and lifestyle – Diets high in red and processed meats and low in fibre are associated with an increased risk. Smoking, excessive alcohol consumption, obesity and physical inactivity also contribute.

  4. Medical conditions – Long-term inflammatory bowel diseases such as ulcerative colitis and Crohn’s disease can increase the risk of bowel cancer.

  5. Type 2 diabetes – There is some evidence linking insulin resistance and metabolic changes in diabetes with a higher incidence of colorectal cancer.

Signs and Symptoms

Bowel cancer can develop silently for years before symptoms appear, which is why screening is so important. However, some warning signs should never be ignored. Common symptoms include:

  • Persistent changes in bowel habits, such as diarrhoea, constipation or a feeling that the bowel doesn’t empty completely.

  • Blood in the stool or rectal bleeding.

  • Unexplained weight loss or loss of appetite.

  • Abdominal pain, bloating or cramping that doesn’t go away.

  • Fatigue caused by anaemia (often from slow internal bleeding).

These symptoms can also be caused by conditions such as haemorrhoids or irritable bowel syndrome (IBS) but if they persist for more than a few weeks it’s essential to consult a doctor.

Screening and Early Detection

Screening programmes are one of the most effective ways to reduce deaths from bowel cancer. Detecting cancer at an early stage dramatically improves the chances of successful treatment. In many countries national screening programmes are available for adults over a certain age.

The faecal immunochemical test (FIT) is commonly used to check for hidden traces of blood in stool samples, which may indicate bleeding from polyps or cancers. If the test is positive a colonoscopy is usually recommended. A colonoscopy allows doctors to view the entire colon using a flexible tube with a camera and remove any suspicious polyps for further analysis.

Other screening tools include CT colonography (a virtual colonoscopy) and sigmoidoscopy, which examines only the lower part of the colon.

Diagnosis and Staging

If bowel cancer is suspected diagnosis is confirmed through imaging tests, colonoscopy and biopsy. Once confirmed further tests—such as CT or MRI scans—are used to determine how far the cancer has spread. Doctors classify bowel cancer in stages:

  • Stage 0 (Carcinoma in situ): Abnormal cells are confined to the inner layer of the bowel.

  • Stage I: The tumour has grown into the bowel wall but not beyond it.

  • Stage II: The cancer has spread through the wall of the colon but not to lymph nodes.

  • Stage III: Cancer has spread to nearby lymph nodes.

  • Stage IV: The cancer has metastasised to distant organs, such as the liver or lungs.

Staging helps guide treatment decisions and provides information about prognosis.

Treatment Options

Treatment for bowel cancer depends on the stage of the disease, the exact location of the tumour and the patient’s overall health. The main treatments include surgery, chemotherapy, radiotherapy and targeted therapies.

1. Surgery

Surgery is the cornerstone of bowel cancer treatment. In early-stage cancers the tumour and surrounding tissue may be removed through local excision or laparoscopic (keyhole) surgery. In more advanced cases a section of the colon or rectum may need to be removed (colectomy) and the remaining parts rejoined. Occasionally, a stoma (an opening in the abdomen for waste) may be necessary, either temporarily or permanently.

2. Chemotherapy

Chemotherapy uses drugs to kill cancer cells or stop them from dividing. It can be given before surgery (to shrink a tumour), after surgery (to reduce recurrence risk) or to control advanced cancer. Common regimens include drugs like 5-fluorouracil (5-FU), capecitabine and oxaliplatin.

3. Radiotherapy

Radiotherapy is more commonly used for rectal cancer than colon cancer, often before surgery to shrink tumours or after surgery to prevent recurrence. It can be combined with chemotherapy in a treatment known as chemoradiation.

4. Targeted and Immunotherapies

Newer treatments target specific molecules involved in cancer growth. For example, drugs such as bevacizumab (Avastin) target blood vessel growth that tumours rely on. Cetuximab and panitumumab target the epidermal growth factor receptor (EGFR), used only when genetic testing shows the tumour will respond.
Immunotherapies, which harness the immune system to fight cancer, have shown promise—particularly in patients with microsatellite instability-high (MSI-H) tumours.

Prognosis and Survival Rates

Survival rates for bowel cancer have improved significantly over the past few decades. When detected early, the five-year survival rate can exceed 90%. However, for stage IV cancers that have spread to distant organs, survival drops considerably. This underscores the importance of early detection through screening and awareness.

Living with and Beyond Bowel Cancer

Recovery doesn’t end with treatment. Many people experience ongoing physical and emotional challenges, including fatigue, digestive changes or anxiety about recurrence. Follow-up appointments, blood tests and imaging scans are part of routine care to detect any signs of recurrence early.

Support groups and counselling services can help patients and families manage the psychological impact of the disease. Dietary changes—such as increasing fibre, eating more fruits and vegetables and limiting red meat—can support long-term gut health and potentially reduce recurrence risk.

Prevention and Lifestyle

While not all cases of bowel cancer can be prevented, healthy lifestyle choices can reduce risk. These include:

  • Maintaining a healthy body weight.

  • Eating a diet rich in fibre, whole grains, fruits and vegetables.

  • Limiting red and processed meats.

  • Exercising regularly.

  • Avoiding smoking and excessive alcohol.

For those with a family history or genetic predisposition, genetic counselling and more frequent screening may be advised.

Final Thoughts

Bowel cancer remains a major health challenge, but it is also one of the most preventable and treatable forms of cancer when detected early. Screening, healthy lifestyle habits and awareness of the warning signs can all make a life-saving difference. Advances in surgery, chemotherapy and precision medicine continue to improve outcomes, giving patients more hope than ever before.

 

Disclaimer:

The information presented in this article is intended for general informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.

Never disregard professional medical advice or delay in seeking it because of something you have read in this article. The content is not intended to be a substitute for professional medical evaluation, diagnosis or treatment. Reliance on any information provided in this article is solely at your own risk.

The author, publisher and website are not responsible for any errors or omissions or for any consequences from application of the information contained herein. If you have or suspect that you have a medical problem contact your healthcare provider promptly. Your health is important and decisions about it should always be made in consultation with a qualified medical professional.

 

Further information: The Bowel Cancer UK website is a great resource for unbiased, factual information on Bowel Cancer, its causes, treatment and prevention, as well as the research they do and how you can support the charity. For further details click here (bowelcanceruk.org.uk)