Bowel Cancer (Colorectal Cancer): Meaning, Symptoms, Diagnosis & Treatment 

Introduction

Have you ever noticed changes in your bowel habits, blood in your stool, unexplained abdominal discomfort, or ongoing tiredness and wondered if it could be bowel cancer? These symptoms can have many causes and may occur with a number of benign (non-cancerous) diseases, but it is important not to ignore them when they persist¹. This article explains everything you should know about bowel cancer in a simple and easy-to-understand way. 

 What Is Bowel Cancer (Colorectal Cancer)?

Large bowel cancer, also called colorectal cancer, is a type of cancer that develops in the large intestine¹. The large intestine includes parts like the colon and rectum, which help the body process waste before it leaves the body². Bowel cancer usually begins when abnormal cells in the inner lining of the bowel (intestine) grow and multiply in an uncontrolled manner. Over time, these cells can form a growth called a tumour and may spread to other parts of the body if not treated¹. 

Types of Bowel Cancer

The different types of bowel or colorectal cancers include: 

• Adenocarcinoma: This is the most common type of bowel cancer. It starts in the gland cells that produce mucus and other fluids in the lining of the colon or rectum. 
• Neuroendocrine Tumours: These cancers develop from specialised cells called neuroendocrine cells. They can occur in different parts of the large intestine. 
• Squamous Cell Carcinoma: This is a very rare form of colorectal cancer that develops from squamous cells, the cells that form the lining of the intestine⁵. 
• Lymphoma: Lymphoma is a cancer that begins in lymphatic tissue. In some cases, it can also occur within the bowel^5,6. 
• Sarcomas: These are the uncommon cancers that develop from the cells of the body’s supporting tissues, such as muscle, bone, connective tissue, or blood vessels. Most common bowel sarcoma is leiomyosarcoma, which begins in the smooth muscle tissue of the digestive tract. A rare type of sarcoma is a gastrointestinal stromal tumour (GIST), which can develop anywhere along the digestive system and is rare in the large bowel⁵. 

Stages of Bowel Cancer

The stage of bowel cancer describes how far the cancer has grown or spread. Bowel cancer is generally divided into Stages 0 to IV: 

• Stage 0: Abnormal or cancerous-looking cells are limited to the innermost lining of the bowel (also known as the mucosa). They have not spread deep into the bowel wall. This is also called carcinoma in situ. 
• Stage I (or 1): The cancer has grown beyond the innermost lining and into the muscle wall but has not reached the nearby lymph nodes or any organs. 
• Stage II (or 2): The cancer has grown through the bowel wall and may have reached the nearby tissues or organs. However, it has not spread to the nearby lymph nodes or other parts of the body. 
• Stage III (or 3): The cancer has spread through the bowel wall to nearby organs or tissues and nearby lymph nodes. However, it has not spread to the distant body parts. 
• Stage IV (or 4): The cancer has moved beyond the bowel and reached other organs or tissues in the body. It may have spread to areas such as the liver or lungs. This spread from its original site to another part of the body is known as metastasis. The cancer cells in these new areas are still colorectal cancer cells, even though they are found in a different organ⁷. 

Note: The exact stage is determined using test results, including examination of the tumour and lymph nodes. The stage may be further divided into Stages 2, 3 and 4 and into sub-stages based on the extent of spread. 

Symptoms of Bowel Cancer

Bowel cancer symptoms in early stages are minimal. However, symptoms can be more noticeable in the later stages and include: 

• Persistent changes in bowel habits, such as diarrhoea or constipation 
• Blood in the stool (the stool may also look black) or bleeding from the rectum 
• A feeling of incomplete bowel movement, even after passing stool 
• Unexplained weight loss 
• Persistent tiredness or weakness (due to anaemia)⁸ 
• Ongoing abdominal pain, cramps or bloating 
• Stools becoming thinner or narrower than usual¹ 
• Mucus in stool 

Causes of Bowel Cancer

Bowel cancer does not usually have one single cause. It develops when changes occur in the DNA of bowel cells, causing them to grow and divide abnormally. These changes can build up over time and may eventually lead to cancer. Important causes include: 

• Inherited Genetic Changes: Some people inherit gene changes from their parents that can make bowel cancer more likely to develop. Certain inherited conditions, such as familial adenomatous polyposis (FAP) and Lynch syndrome, can increase the risk of colorectal cancer. 
• Long-term Inflammation: Conditions such as ulcerative colitis (causes ongoing inflammation and sores in the lining of the bowel) and may increase the risk of colorectal cancer over time. 
• Precancerous Growth: Some polyps or growths, such as adenomas, can gradually develop into cancer if they are not detected and removed⁹. 

Risk Factors

A risk factor is something that increases the likelihood of a disease. The risk factors for bowel cancer include: 

• Age: The likelihood of bowel cancer generally increases with age, increasing steeply after the 50 and 60 years of age. 
• Family History: Having one or more close family members who have had bowel cancer can increase the risk. 
• Tobacco: Smoking and tobacco use are linked with a higher risk of developing bowel cancer. 
• Alcohol: Drinking  alcohol regularly may increase the risk. 
• Overweight: Excess body weight or being obese is associated with a greater likelihood of bowel cancer. 
• Reduced Physical Activity: Not spending enough time being physically active may increase the risk. 
• Diet: A diet high in processed meat (such as smoked or extra-salted) and red meat, and low in fibre-rich foods may be associated with a higher risk¹⁰. 

Note: Although these factors increase the risk of developing the disease, having one or more of them does not necessarily mean that a person will develop bowel cancer or that people with none of these risk factors may not develop bowel cancer. Bowel cancer may also occur in people who have no known risk factors. 

Diagnosis

Bowel cancer is diagnosed using a combination of medical history, physical examination and tests. The doctor may use the following strategies to diagnose a bowel cancer: 

• Medical History: The doctor asks about bowel-related symptoms, such as changes in bowel habits, blood in the stool, abdominal pain, unexplained weight loss or persistent tiredness. They may also consider factors such as older age (people over 50 years old have increased risk), a family history of bowel or colorectal cancer, previous bowel polyps, or long-term inflammatory bowel disease. 
• Clinical Evaluation: They might perform a physical examination to assess the abdomen and check for signs that may require further investigation. 
• Stool Tests (FIT/Fecal occult blood): A small stool sample may be checked for hidden blood that cannot be seen with the naked eye. Finding blood in stool does not necessarily mean cancer is present, but it may indicate the need for further testing. 
• Tumour Marker Tests: Tumour markers are substances that may be produced by cancer cells or by the body in response to cancer. They can be measured in blood, urine or tissue samples. In bowel cancer, a tumour marker called carcinoembryonic antigen (CEA) may be checked. CEA levels can help monitor the response to treatment and look for signs that the cancer may have returned. However, CEA testing alone cannot confirm bowel cancer. 
• Colonoscopy, Sigmoidoscopy and Biopsy: The doctor might examine the inside of the rectum and colon (or the entire large intestine) using a thin, flexible tube with a camera. If an unusual area or polyp is found, a small tissue sample may be removed for testing (biopsy) and confirmation of the diagnosis of bowel cancer. 
• Imaging Tests: Scans such as computed tomography (CT) or magnetic resonance imaging (MRI) may be used to understand the size and location of a tumour and check whether the cancer has spread to nearby or distant parts of the body¹¹. 

Bowel Cancer Treatment Options

Bowel cancer treatment depends on factors such as the location and stage of the cancer, its size and the person’s overall health. Doctors may use one treatment or combine several approaches. 

1. Surgery

Surgery is an important treatment for many colorectal cancers, and it may be performed during different stages of the cancer as needed. The surgeon removes the cancer along with an appropriate area of surrounding tissue. Nearby lymph nodes will also be removed and examined. The healthy ends of the bowel are then joined back together. 

Examples: Hemicolectomy or total colectomy. In case of polyps (which may be precancerous) polypectomy or endoscopic submucosal dissection can be performed for complete & safe removal. 

2. Chemotherapy

This treatment uses medicines that destroy cancer cells or stop them from multiplying. It may be given in different forms, such as an injection or tablets to be taken orally. Chemotherapy may be done after surgery to reduce the risk of cancer returning, before surgery in selected cases (to shrink the tumour), or for advanced disease. 

Examples of chemotherapy medicines: Leucovorin, capecitabine, and oxaliplatin. 

3. Radiation Therapy

This method uses high-energy radiation to destroy cancer cells. Radiation therapy can be external (radiation is given using a machine, outside the body, to the area where cancer is present) or internal (sending radioactive waves directly into the cancer cells or near them). It may be given before or after surgery depending on the need. 

4. Targeted Therapy

This treatment uses specific medicines that act on specific cancer cells. The doctor may choose the type of medicine based on the biomarker test. It may be given alone or with chemotherapy. 

Examples of targeted therapy medicines: Encorafenib, bevacizumab, and panitumumab. 

5. Immunotherapy

This method uses medicines that help the immune system recognise and attack cancer cells. The doctor may choose the type of medicine based on the biomarker test. It may be suitable for certain colon cancers with specific characteristics. 

Examples of immunotherapy agents: Ipilimumab, nivolumab, and pembrolizumab¹². 

Note: When colorectal cancer has spread to the distant organs, treatment may include a combination of chemotherapy, targeted therapy, immunotherapy and surgery or other local treatments in selected patients. The treatment plan is individualised based on the area of spread of cancer. 

How to Prevent Bowel Cancer?

Although not all bowel cancers can be prevented, certain lifestyle changes may help reduce its risk. These include: 

• Eating plenty of vegetables, fruits, whole grains and other fibre-rich foods. Also, including low-fat dairy products like cheese and yoghurt in the diet. 
• Reducing the frequent consumption of red meat and processed meat. 
• Engaging in physical activity every day for at least 30 minutes. 
• Limiting the consumption of alcohol. 
• Avoiding smoking and using other tobacco products¹. 
• Discussing long-term bowel problems or other high-risk conditions with the doctor along with your medical and family history, which may need individualised supervision. 

Note: These lifestyle measures may help lower the risk of bowel cancer, but they cannot guarantee that cancer will be prevented. Some people may develop bowel cancer even after following a healthy lifestyle.  

When to Consult a Doctor?

It is important to seek medical advice if you have any of the following: 

• Blood in the stool 
• Persistent changes in bowel habits 
• Frequent abdominal pain or bloating 
• Unusual tiredness 
• Unexplained weight loss 
• A family history of colorectal cancer or an inherited condition that increases cancer risk 
• Previous history of bowel polyps or cancer 

You may require urgent medical attention if you have symptoms like heavy bleeding through the rectum, bloody diarrhoea, and severe abdominal pain^1,8. 

Also Read: Is Bowel Leakage a Sign of Cancer?

Conclusion

Understanding the meaning of bowel cancer can help you recognise the disease and its warning signs early. Regular screening, a healthy lifestyle and timely medical advice can lower the risk and support early detection. If you notice ongoing changes in your bowel habits or other unusual symptoms, consult a doctor without delay. 

Frequently Asked Questions (FAQs)

References

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12. Colon cancer treatment. NCI. 2025. Accessed August 17, 2026. https://www.cancer.gov/types/colorectal/patient/colon-treatment-pdq  

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14. Passing wind. Cancer Research UK. 2025. Accessed August 17, 2026. https://www.cancerresearchuk.org/about-cancer/coping/physically/bowel-problems/types/passing-wind  

15. Skalitzky MK, Zhou PP, Goffredo P, et al. Characteristics and symptomatology of colorectal cancer in the young. Surgery. 2023;173(5):1137-1143. doi:10.1016/j.surg.2023.01.018. https://pubmed.ncbi.nlm.nih.gov/36872174/ 

16. Anal pain. healthdirect. 2024. Accessed August 17, 2026. https://www.healthdirect.gov.au/anal-pain  

17. Tsokkou S, Konstantinidis I, Papakonstantinou M, et al. Sex differences in colorectal cancer: Epidemiology, risk factors, and clinical outcomes. J Clin Med. 2025;14(15):5539. doi:10.3390/jcm14155539. https://pubmed.ncbi.nlm.nih.gov/40807160/  

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