Colon Cancer: Causes, Symptoms, Treatment & Prevention

Cancer that forms in the large intestine is known as colon cancer, while cancer in the rectum is called rectal cancer. Cancers that affect any of these organs may be called colorectal cancer. Most colorectal cancers develop over time from abnormal polyps. Colon cancer is a form of cancer that impacts the colon or rectum. Your colon and rectum are the parts of your digestive system that help you process food. The symptoms, treatment, and outlook for colon cancer will vary depending on the stage your cancer is in when you are first diagnosed.

Causes

The precise cause of most colon cancers is still unknown. However, the disease begins when cells in the colon undergo DNA mutations. A cell’s DNA contains instructions that regulate its function. When these mutations occur, they trigger rapid cell growth and prevent normal cell death.

As a result, an excess of abnormal cells forms, potentially leading to a tumor. These cancer cells can spread and harm healthy tissues. Over time, they may break away and spread to other parts of the body, a process known as metastasis.

Symptoms and Signs

• Diarrhoea or constipation
• Changes in stool consistency
• There could be blood in your stool, which might make it look dark brown or black.
• Bright red bleeding from the rectum
• Abdominal pain, cramping, bloating, or gas
• Constant urge to defecate despite passing stools
• Weakness and fatigue
• Irritable bowel syndrome
• Iron deficiency anaemia

Weight loss and abdominal pain usually occur as the disease progresses in the later stages.

The earliest signs of colon cancer may go unnoticed, but symptoms may become more noticeable as the cancer progresses. People with symptoms in the early stages may include

• Bloody stool
• Bowel movement changes, like passing loose stools, having difficulty with bowel movements, or noticing stools that are unusually thin.
• The feeling of not having emptied the intestines after passing stools.
• Abdominal pain, cramps, or bloating
• Nausea and vomiting
• Anaemia due to intestinal bleeding
• Decreased appetite
• Fatigue and weakness
• Unexplained weight loss

Colon cancer can affect various parts of the colon, including:

• The colon
• Ascending colon
• Transverse colon
• Descending colon
• Sigmoid colon

Stages

Cancer is classified from stage 0, the earliest stage, to stage 4, the most advanced. Here’s how stages are defined:

• Stage 0: Stage 0 is also called carcinoma. At this stage, the abnormal cells have not spread beyond the colon or rectum’s inner lining.
• Stage 1: Cancer has grown into the surrounding tissue.
• Stage 2: The cancer has spread to the outer layers of the colon but has not extended beyond it.
• Stage 3: Cancer has grown through the colon’s outer layers and reached one to three lymph nodes.
• Stage 4: The cancer has extended beyond the colon wall into surrounding tissues.

Symptoms of Colon Cancer Based on Stages

Stage 1	Stage 2	Stage 3	Stage 4
Constipation	Constipation	Extreme Fatigue	Jaundice
Diarrhoea	Diarrhoea	Unexplained weakness	Difficulties in breathing
Changes in the faeces, such as color and shape	Changes in the faeces, such as color and shape	Losing weight unintentionally	Swollen hands and feet
Bloody stool	Bloody stool	Changes in the stool that last longer than a month	Chronic Headaches
Bleeding from the rectum	Bleeding from the rectum	Feeling like your bowels won’t empty utterly
Excess gas	Excess gas	Vomiting
Abdominal pain and cramps	Abdominal pain and cramps

Risk Factors

Some risk factors you can’t control include being over 50 and genetic conditions such as Lynch syndrome and familial adenomatous polyposis (FAP) greatly increase the risk of colon cancer. People with a first-degree family member (parent, sibling, or child) diagnosed with colon cancer or colorectal polyps have an increased risk. A personal history of colon cancer or polyps further elevates the likelihood of developing the disease.

Avoidable risk factors for the disease include being overweight or obese, smoking, drinking heavily, having type 2 diabetes, having a sedentary lifestyle, and consuming a diet high in processed meats.

Diagnosis

Doctors diagnose colon cancer through a step-by-step process. They first ask about symptoms such as changes in bowel habits, bleeding, stomach pain, or unexplained weight loss. They also review medical history and family history because some people may have a higher risk. After this, a physical examination may be done to check the abdomen or rectum for any unusual signs.

Main Test for Detection

The most reliable test for colon cancer is a colonoscopy. In this procedure, a thin tube with a camera is passed through the rectum to examine the colon. It helps doctors find polyps, sores, or abnormal growths. Polyps can often be removed during the test before they become harmful.

Confirming Cancer Cells

If doctors notice a suspicious area, they collect a small tissue sample. This is called a biopsy. Specialists study the sample under a microscope to confirm whether cancer cells are present and identify the type of cancer.

Supportive Screening Tests

Some simple stool tests can detect hidden blood that cannot be seen easily. These tests may suggest a problem in the colon and help decide if a colonoscopy is needed.

Blood Work

Blood tests cannot confirm colon cancer on their own, but they provide helpful clues. They may show low red blood cell levels caused by slow internal bleeding. Doctors may also check certain markers, such as CEA, to monitor treatment later.

Scans to Check Spread

Imaging tests help doctors understand where the cancer is located and whether it has spread. Common scans include CT scan, MRI, PET scan, ultrasound, and chest X-ray. These tests help create the best treatment plan.

Understanding the Stage

Once cancer is confirmed, doctors assign a stage. Staging explains how deeply the cancer has grown and whether it has reached lymph nodes or other organs. Stage 0 is the earliest stage, while Stage 4 means the cancer has spread to other distant parts of the body.

Treatment

Treatment for colon cancer depends on the cancer stage, tumor size, where it is located, and the person’s overall health condition. Doctors may use one treatment or combine different treatments for better results. The main goal is to remove the cancer, stop its spread, and improve quality of life.

Surgery

Surgery is the most common treatment for colon cancer, especially when found early. Doctors remove the cancerous part of the colon along with nearby lymph nodes.

In very early cases, the cancer may be removed during a colonoscopy if it is only inside a polyp. This is called a polypectomy.

If the cancer has grown deeper, doctors may perform a colectomy. In this procedure, they remove the affected part of the colon and join the healthy ends together.

Sometimes the bowel needs time to heal after surgery. In such cases, doctors create an opening in the abdomen for waste to pass into a bag. This is called a colostomy. It may be temporary or permanent.

Chemotherapy

Chemotherapy uses medicines to destroy cancer cells. Doctors may give it after surgery to kill any remaining cancer cells and lower the chance of the cancer returning.

It may also be given before surgery to shrink a large tumor and make removal easier. In advanced stages, chemotherapy can slow cancer growth and help control symptoms.

Common side effects may include tiredness, nausea, diarrhoea, and hair thinning.

Radiation Therapy

Radiation therapy uses high-energy rays to kill cancer cells. It is used less often for colon cancer than for rectal cancer, but it may help in some cases.

Doctors may use radiation to shrink a tumor before surgery or reduce pain, bleeding, or blockage in advanced cancer.

Targeted Therapy

Targeted therapy uses medicines designed to block certain changes that help cancer cells grow. These medicines can slow or stop cancer growth while causing less damage to healthy cells.

Doctors usually use targeted therapy for advanced colon cancer or when the cancer returns.

Immunotherapy

Immunotherapy helps the body’s immune system find and fight cancer cells. It works best for certain types of colon cancer with specific genetic features.

This treatment may be used when cancer has spread or other treatments are not enough.

Palliative Care

Palliative care focuses on reducing pain and managing symptoms during treatment. It can help improve comfort, emotional well-being, and daily life. Patients can receive palliative care along with other cancer treatments.

The Screening Process

Various tests are available to screen for colorectal cancer. Some of these tests can detect cancerous cells, while others help determine the extent or location of the disease.

If cancer has spread. Although colonoscopy is most recommended. The other most common screening tests include:

• Fecal immunochemical test
• Fecal DNA test
• Flexible sigmoidoscopy
• Guaiac-based fecal occult blood test
• Colonoscopy
• CT colonography
• Double-contrast barium enema

Prevention

Certain risk factors for colon cancer, including family history and age, are beyond prevention. Lifestyle choices that contribute to colon cancer are preventable, and modifying them may lower your risk of developing the disease. Here are some things you can do to reduce your risk of developing colon cancer.

• Reduce the amount of red meat
• Avoid processed meats
• Eat more plant foods
• Reduce dietary fat
• Exercise every day
• Lose weight if recommended by your doctor
• Quit smoking
• Reduce drinking
• Reduce stress
• Manage existing diabetes

Frequently Asked Questions