Colon Cancer: Types, Causes, Risk factors, Symptoms, Treatment & Prevention

Colon cancer definition

Colon Cancer, also called colorectal cancer (CRC), is a type of cancer that originates from the rectum or colon. It usually starts when abnormal cells grow out of control and invade the wall of the rectum and neighbouring tissue. The colon is part of the body's digestive system and the first and longest part of the large intestine. 

Colon cancer primarily affects the large intestine, which is where waste materials from digestion accumulate. The colon is responsible for absorbing vitamins and nutrients from digested food and converting the remaining waste products into stool (poop). The rectum stores stool and is the lower part of the large intestine.

Colon cancer meaning

The term "colon" is derived from the Greek word “kolon”, which refers to the large intestine. The word "cancer" is derived from the Greek word “karkinos”, meaning crab, which refers to the shape of the tumors and their ability to spread to other body parts, similar to the way a crab's legs extend.

Colon cancer prevalence

According to the World Health Organization (WHO), colon cancer is the 2nd leading cause of cancer deaths worldwide, representing about 10% of all cancer cases. Globally, it is the 3rd most common cancer, with over 0.19 crore new cases and more than 930,000 deaths estimated in 2020.

Colon cancer incidence varies by region and age group. The incidence of colon cancer (CRC) in India is lower as compared to developed countries. However, the incidence has been increasing in recent years. 

Currently, colon cancer is the 7th most common cancer in India, and the number of cases is rising, with a 20% increase from 2004 to 2014, with 65,358 new cases in 2021. It primarily affects older individuals, predominantly those aged 50 and above.

Types of colon cancer

Colorectal cancer can be classified into several types depending on the location, cell type and growth patterns. The different types of colon cancer include:

Adenocarcinoma

It is the most common type of colon cancer, accounting for about 95% of all cases. It originates from the glandular cells that line the inside of the colon and rectum. Typically, it starts as a tissue growth called a polyp. Specifically, adenomas may develop into cancer.

Adenocarcinomas are classified into two less common subtypes:

• Mucinous adenocarcinoma: This tumor consists of approximately 60 percent mucus. The presence of mucus may lead to quicker and more aggressive cancer cell spread compared to typical adenocarcinomas. Mucinous adenocarcinomas represent about 10 to 15 percent of all rectal and colon adenocarcinomas.
• Signet ring cell adenocarcinoma: Signet ring cell adenocarcinoma represents less than 1 percent of all colon cancers. Its name derives from its distinctive appearance under a microscope and is often aggressive, making treatment more challenging.

Carcinoid Tumours

These are rare, slow-growing tumors that begin in the hormone-producing cells of the colon. They are typically less aggressive than adenocarcinomas.

Gastrointestinal Stromal Tumours (GISTs)

These are the rare types of colon cancer tumors that develop in the connective tissue of the digestive tract, including the colon. They are typically treated differently from other forms of colon cancer.

Lymphoma

Though rare, lymphoma can also affect the colon and rectum, primarily arising from lymphatic tissue.

Colon cancer symptoms

Colon or colorectal cancer may not show any noticeable symptoms, particularly in the early stages, which is why screening is so important. However, some common colorectal cancer symptoms include:

Symptoms of colon cancer in men

• Changes in bowel habits: This may include diarrhoea, constipation, or a change in stool consistency that lasts more than a few days.

• Blood in the stool: Either bright red or dark, tarry stools can indicate bleeding in the colon or rectum.

• Unexplained weight loss: Significant weight loss without a known cause.

• Abdominal discomfort: Cramping, bloating, or pain in the abdomen, which may be persistent.

• Fatigue: Extreme tiredness or weakness that doesn't improve with rest.

• Feeling that the bowel does not empty completely: A sensation of incomplete evacuation.

• Iron-deficiency anaemia: This can occur if the cancer causes slow internal bleeding, which decreases red blood cells.

Colon cancer recurrence symptoms may include abdominal pain, changes in bowel habits, unexplained weight loss, fatigue, and blood in the stool.

Symptoms of colon cancer in women

Colon cancer symptoms are similar in both men and women, including changes in bowel habits, blood in stool, and abdominal pain. However, women may experience more vague symptoms like fatigue or unexplained weight loss.

Colon cancer causes

Colon cancer develops as a result of a combination of genetic, lifestyle, and environmental factors. Some common colorectal cancer causes include:

• Genetic Mutations and DNA Changes: Colon cancer typically begins when healthy (normal) cells in the colon develop mutations in their DNA, which leads to uncontrolled cell growth. Genetic mutations like Lynch syndrome and familial adenomatous polyposis (FAP) also contribute.

• Diet High in Red and Processed Meats: A diet rich in red meats (pork, beef, liver or lamb) and processed meats increases the risk of colorectal cancer.

• High-Temperature Cooking Methods: Cooking meats at very high temperatures (such as frying, broiling, or grilling) can create chemicals that may raise the risk of developing colon cancer.

• Low Vitamin D Levels: Vitamin D deficiency has been associated with an increased risk of colorectal cancer.
  

Colon cancer risk factors

Understanding colorectal cancer risk factors helps identify high-risk persons who may benefit from early screening and preventive measures. The following are some of the key factors which play a major role in increasing the chances of developing colon cancer by influencing the body's biology and the likelihood of genetic mutations.

• Age: Colorectal cancer risk increases as a person ages. It is increasing among individuals younger than 50, and the exact reason remains unclear. Younger adults can also get it, but it is more common after age 50.

• Gender: Men who have colorectal cancer are more likely to die from it than women. The exact reasons are not fully clear. It is also possible for women to develop this disease after they reach menopause. Women with colorectal cancer are more likely to have right-sided colon cancer, especially if they are postmenopausal.

• Family History: A family history of colon cancer or polyps increases the risk. People who have a first-degree relative, such as a parent, sibling, or child, with a colorectal cancer history are at an increased risk of developing the disease themselves. This risk is even greater if the relative was diagnosed before age 50 or if more than one first-degree relative has been diagnosed.

• Physical Inactivity: Lack of exercise or a sedentary lifestyle can lead to weight gain and increased inflammation, both of which are linked to a higher risk of colon cancer by promoting abnormal cell growth in the colon.

• Cholecystectomy: Patients who have had their gallbladder removed may have a slightly elevated risk of right-sided colon cancer, although the reasons for this link are not yet fully understood.

• Diet: Processed meats, diets high in red meats and low in fibre can raise the risk of colon cancer.

• Obesity: Obesity can increase the risk of colon cancer by causing chronic inflammation and altering hormone levels, promoting the growth of cancer cells in the colon.

• Past history of particular conditions: 
• Inflammatory bowel disease (IBD): If the patient has an IBD condition, including either Crohn's disease or ulcerative colitis, the colorectal cancer risk is increased.
• Having a history of adenomatous polyps (adenomas) can raise the risk of developing colorectal cancer, especially if the polyps are large, if any of them show dysplasia, or if there are multiple numbers of polyps.
• The study indicated that people with diabetes have a 47% greater risk of developing colorectal cancer compared with people without diabetes.

• A past history of radiation to the pelvis area or abdomen: If the person has received radiation to the abdomen or pelvis area, particularly as a child, that person may need to start getting screened for colorectal cancer when the person is younger and be screened more often. 

• Smoking and Alcohol Use: Excessive alcohol consumption and cigarette smoking are linked to a higher risk of colon cancer.

Complications of colon cancer

Complications of colon cancer significantly affect the patient's quality of life and can depress the prognosis by causing additional health issues. Below mentioned are some of the complications associated with colon cancer:

• Metastasis (Cancer Spread): Colon cancer can spread to other organs, especially the liver and lungs, causing additional health problems.

• Bowel obstruction: A tumor can block the colon, leading to bowel obstruction, which causes severe abdominal pain, nausea, and vomiting.

• Perforation: In some cases, the tumor can cause the colon to rupture, leading to peritonitis, a severe abdominal infection.

• Bleeding: Colon cancer may cause internal bleeding, leading to anaemia or the need for blood transfusions.

• Emotional and Psychological Impact: The diagnosis and treatment of colon cancer can lead to mental health challenges, including anxiety and depression.

Identifying and understanding these complications help to guide appropriate treatment and management, improving outcomes and alleviating suffering.

Colon cancer diagnosis

Many healthcare professionals recommend adults start colon cancer screening at age 45. To diagnose colon cancer, the healthcare team uses a combination of certain tests, including:

• Medical history and physical exam
• Imaging Tests
• CT scan
• MRI
• X-rays
• Blood Tests 
• Complete blood count (CBC), 
• Liver function tests (LFTs) and tumor markers (e.g., CEA)
• Biopsy
• Stool tests
• Guaiac faecal occult blood test (gFOBT) 
• Faecal immunochemical test (FIT or iFOBT)
• Multitarget stool DNA testing (sDNA-FIT)
• Direct visualization tests
• Colonoscopy
• Virtual colonoscopy
• Sigmoidoscopy
• Other methods
• Double-contrast barium enema (DCBE)
• Single-specimen gFOBT performed in a doctor's office
  

Colon cancer treatment

Colorectal cancer treatment options depend on the tumor location, stage of the cancer and the overall health of the patient. Common treatment options include:

• Surgery
• Colectomy
• Chemotherapy
• Radiation Therapy
• Targeted Therapy
• Immunotherapy
• Palliative Care
  

Colon Cancer Prevention

While it may not be possible to completely prevent colorectal cancer, people can take steps to decrease their risk through lifestyle changes and by avoiding risk factors that contribute to its development. Here are some key preventive measures:

• Regular screening: Regular screenings such as colonoscopies allow for early detection of colon cancer in individuals over 50 or with other risk factors, leading to better outcomes in their treatment.

• Following a healthy diet: A diet abundant in fruits, vegetables, and fibre limits processed foods, red meats, and alcohol, which have a potential role in reducing colon cancer risk.

• Exercising regularly: Being physically active regularly reduces the risks of colon cancer.

• Quitting Smoking: Staying away from tobacco smoke is one of the best preventive measures against cancer.

• Maintaining a healthy weight: Being overweight or obese raises risk, so staying at a normal weight can reduce the likelihood of cancer.

• Limiting Alcohol: Limiting alcohol consumption is an essential factor for preventing colon cancer.

Difference between IBS and Colon cancer

IBS vs Colon cancer

Though both IBS and colon cancer affect the gastrointestinal tract, the most significant difference lies in their underlying causes, clinical behaviour, and severity. Below is a comparison of these two conditions: