Bowel (Colorectal) Cancer

Bowel cancer, also called colorectal cancer, starts anywhere in the large intestine or bowel, the organ that moves digested food through your body. It’s the third most common cancer worldwide, accounting for 10% of all cancer cases (1).

Colorectal cancer treatment depends on where the cancer started and how much it has grown and spread. Supporting your nutrition and overall health can make a meaningful impact on your treatment and recovery.

Keep reading to learn more about the causes, diagnosis, treatments, and ways to support your body during bowel cancer treatment and beyond.

Colorectal cancer starts when abnormal cells grow uncontrollably anywhere in the large bowel, a 1.5-metre (5-foot-long), tube-shaped digestive organ that includes the colon and rectum. Cancer that starts near the end of the bowel, in the rectum and anus, is called rectal and anal cancer, respectively. Anal cancer, on its own, is considered a separate type of cancer.

The large bowel plays several important roles in digestion, including: 

• Absorbing water and electrolytes from digested food
• Absorbing certain vitamins produced by bacteria that live in the colon
• Turning food waste into solid stool (faeces)
• Pushing faeces out of your body through the rectum and anus 

Most colorectal cancers start as small, noncancerous growths called polyps that form on the inner lining of the large intestine. Polyps can change over time, and some types may turn into cancer [2]:

• Adenomas are considered precancerous because many turn into cancer over time.
• Hyperplastic and inflammatory polyps are the most common type, but they usually don’t become cancer. 
• Sessile serrated polyps (SSP) and traditional serrated adenomas (TSA) carry a higher risk of becoming cancerous.

A screening colonoscopy allows doctors to find and remove polyps before they become bowel cancer.

There is no single known cause of bowel cancer, but these factors can increase your risk [2,3]:

• Age - It’s most common in adults over 55, but rates have been increasing among young adults, and doctors aren’t sure why. 
• A family history of bowel cancer
• Genetic conditions such as Lynch syndrome or familial adenomatous polyposis (FAP)
• A personal history of colorectal polyps
• Inflammatory bowel disease, like Crohn’s disease or ulcerative colitis
• Type 2 diabetes
• Being overweight
• A diet high in red or processed meats like burgers, sausages or bacon
• Heavy alcohol use
•  Smoking
• A sedentary lifestyle

Some people develop bowel cancer without having any identifiable cause.

Bowel cancer symptoms can vary from person to person. Early cancer might not cause symptoms, or they may be vague and easy to dismiss. Colorectal cancer that has spread might cause [3]:

• A change in bowel habits such as diarrhoea or constipation
• Feeling like your bowel does not empty fully
• Bloody or black, tarry stools
• Persistent abdominal pain or discomfort
• Bloating
• Unexplained weight loss
• Fatigue

Other conditions besides cancer can cause these symptoms, but they’re worth mentioning to your doctor, so they can check them out.

If you have symptoms, your doctor will examine you and ask about your family health history. They may order these tests [2,3]:

• A faecal immunochemical test (FIT), a home test that checks a stool sample for hidden blood
• Blood tests to check for anaemia, overall health, and in some cases blood markers that may help with treatment planning of follow-up
• Visual tests like a sigmoidoscopy or colonoscopy, which use a thin tube with a camera to examine the inside of your large intestine
• A biopsy to collect and test a tissue sample for cancer cells
• Imaging tests like a CT, X-ray, ultrasound, MR, or PET/CT to see if cancer has spread to other parts of your body

If tests confirm colorectal cancer, your doctor will stage it to help guide the best treatment for you. Staging refers to how much the cancer has grown or spread. The exact number of lymph nodes involved and the depth of tumour matter for treatment decisions [3].

• Stage 0 means cancer is only in the innermost layer of the colon or rectum.
• Stage I has grown within the inner layer of the colon or rectum, but hasn’t spread to any lymph nodes or elsewhere in the body.
• Stage II has grown into the muscle, the outermost layer or through the wall of the colon or rectum. It has not spread to lymph nodes or distant sites, but it may have spread to nearby tissues or organs.
• Stage III has spread to as many as seven lymph nodes or to areas of fat near lymph nodes, but not to any distant parts of the body.
• Stage IV is late-stage (metastatic) cancer that has spread to nearby lymph nodes, the peritoneum (the tissue that covers the outside of the bowel), other organs, or other parts of the body, such as the liver or lungs.

Bowel cancer treatments depend on the location and stage of your cancer. Your oncologist may recommend one or more of these treatments [3]:

• Surgery to remove the diseased part of the colon or rectum, along with nearby lymph nodes, so the healthy sections can be reconnected. In rare situations, doctors may remove the entire colon (a colectomy). Colon cancer is primarily treated with surgery and/or chemotherapy. During surgery, your doctor may also create a stoma, an opening from the bowel to the outside of your belly that lets stool pass into a disposable bag instead of through your rectum and anus
• Chemotherapy uses medicines to kill cancer cells or shrink tumours
• Radiotherapy uses high-energy rays to kill cancer. It’s commonly used to treat rectal cancer. Rectal cancer also often involves preoperative chemoradiotherapy to improve local control and preserve the sphincter muscle.
• Targeted therapy is a drug that targets specific proteins cancer cells need to grow and multiply. Eligibility depends on whether specific biomarkers are present. Treatments may not be given without biomarker testing.
• Immunotherapy helps your own immune system recognise and destroy cancer cells. This treatment is also biomarker-dependent.

Every recovery looks different. Yours largely depends on the cancer’s stage at diagnosis, your treatment course, and overall health. Your doctor can give you the most accurate information about what you might expect in the future.

Generally speaking, catching cancer early leads to more treatment options and often a better outcome. Many early-stage bowel cancers can be cured after treatment. Your cancer may also go into remission, which means that signs and symptoms are gone and the cancer is under control but not necessarily cured.

Because some cancers can recur or return after treatment, staying on top of your follow-up care, which likely includes regular colonoscopies, CEA blood tests, and imaging according to guidelines, is vital for your long-term health.

Treatments for colorectal cancer can take a toll on your appetite, weight, energy, and overall well-being. You might experience short- or long-term side effects such as:

• Loss of appetite
• Taste changes
• Nausea or vomiting
• Early fullness
• Mouth sores
• Weight loss
• Fatigue
• Gas or bloating
• Diarrhoea or constipation
• Bowel or urinary incontinence

You don’t have to manage these alone. Your care team can offer medications and therapies to help ease them.

Nutrition therapy is especially important during treatment and recovery to help you maintain your strength, prevent malnutrition, and normalise bowel function. After bowel surgery or if you have a stoma, an oncology dietitian and a stoma nurse can help you adjust fibre intake, prevent blockages, manage output, and maintain hydration and electrolyte balance. Long-term changes in bowel frequency or urgency are common and can often be improved with diet and medications prescribed by your dietitians in conjunction with the medical team.

Your dietitian can also create a personalised nutrition plan to help you meet your calorie, protein, and other nutritional needs and troubleshoot eating or digestive problems. They may advise you to:

• Eat smaller, more frequent nutritious meals and snacks
• Prioritise high-protein foods and beverages
• Manage dietary fibre to reduce diarrhoea, constipation, and the risk of intestinal blockages
• Add oral nutrition supplements like shakes, powders, or puddings that provide extra protein and calories in a small volume
• If certain foods worsen digestive symptoms during treatment, work with a dietitian who can help identify foods that are contributing to symptoms and suggest appropriate alternatives.

A cancer diagnosis can feel overwhelming, but your medical team will support you throughout every step, from diagnosis through recovery. Stay in close contact, ask questions, and flag any problems or challenges you have.