Overview
Colon cancer happens when the cells in the large intestine (colon) start dividing uncontrollably. In most cases, colon cancers start as small-size, non-cancerous outgrowths called polyps. Over time, a few polyps become colon cancers.
Sometimes, colon cancer is referred to as colorectal cancer, a term that combines colon cancer with rectal cancer – a type of cancer that forms in the rectum lining.
Increased consumption of fast food that lacks fibre content is observed to be one of the reasons for the increased incidence of colon cancer in India.
Types
Based on the type of cell that they originate from, colon cancer is categorised into the following types:
- 1. Adenocarcinoma: Adenocarcinoma arises from the cells that line the inner surface of the large intestine. This is the most common type of colon cancer.
- 2. Gastrointestinal Stromal Tumours (GISTs): Gastrointestinal stromal tumours (GISTs) form in the interstitial cells of Cajal (ICCs), which are the special cells that line the GI tract wall. These cells are responsible for the contraction of the GI tract when the food and liquids pass along.
- 3. Carcinoid Tumours: Carcinoid tumours are slow-growing and form in the hormone-producing cells present in the GI tract. Carcinoid tumours do not show any symptoms in the early stages.
- 4. Lymphoma: Colon lymphoma forms in the lymph tissue of the large intestine. This is a rare form of colon cancer.
Symptoms
In most cases, colon cancers show no symptoms in the early stages, and even if they do, they are vague. Following are the key symptoms that are associated with colon cancer:
- Presence of blood in stools
- Bowel changes that last for weeks – constipation, diarrhoea, etc.
- Frequent urge to have a bowel movement
- Abdominal cramping
- Stomach pain and bloating
- Feeling weak
- Unexpected weight loss
- Anaemia
Causes
A large percentage of colon cancers (80%) are caused due to environmental factors, whereas a small percentage of cancers (20%) are caused due to genetic factors. Following are a few important risk factors that are associated with colon cancers:
- Presence of Polyps: The presence of benign, non-cancerous lumps, which are called polyps, increase the risk of colon cancer,
- Obesity: Being overweight or obese increases one’s risk of developing colon cancer.
- Unhealthy Food Habits: Following a diet that is rich in processed fat and has low fibre content contributes to increased colon cancer risk. Increased consumption of red meat is also an important risk factor for colon cancer.
- Physical Inactivity: Having a sedentary lifestyle may lead to increased colon cancer risk.
- Smoking: Certain chemicals present in tobacco increase colon cancer risk.
- Alcohol: Moderate to heavy alcohol usage increases one’s risk of developing colon cancer.
- Age: The risk of getting colon cancer increases with age.
- Family History of Colon Polyps: Those with a family history of colon polyps have a higher risk of colon cancer.
- History of Inflammatory Bowel Disorders: Those with a personal history of inflammatory bowel disorders, such as ulcerative colitis and Crohn’s disease also have an increased risk of colon cancer.
Diagnosis
In most cases, colon cancers will not have any symptoms in the early stages; they become more apparent when the disease reaches the advanced stages. Therefore, high-risk individuals should consider regular screening, which helps in early detection and on-time treatment.
Following are the common testing methods recommended for the detection and diagnosis of colon cancer:
a. Physical Exam and Medical History Assessment: Initially, the doctor conducts a thorough medical history assessment and physically examines the patient to understand the cause of the symptoms experienced.
b. CEA Blood Test: Carcinoembryonic antigen or CEA is a special type of protein released by colon cancer. However, the presence of CEA in the blood does not confirm a colon cancer diagnosis as CEA levels are elevated as a result of other health conditions too. This test may be recommended during the treatment to assess the tumour’s response to the treatment given.
c. Faecal Occult Blood Test: This is also the screening test recommended for colorectal cancers. This test examines the stool sample for blood content that is not visible to the naked eye. This test is highly helpful in early detection as the presence of blood in the stools is one of the first symptoms of colon cancer.
d. Colonoscopy: During the colonoscopy, the doctor inserts a slender and flexible tube into the colon through the rectum to check the colon and rectal canals for polyps. In a few cases, the polyps are removed during the colonoscopy. At times, the doctor may also collect the biopsy sample during the colonoscopy. This is an outpatient procedure that is performed with the help of a sedative.
e. Biopsy: During the biopsy, a small sample of the tissue from the suspected area is collected and examined under the microscope for the presence of cancerous cells.
f. Imaging Tests: MRI scans, PET/CT scans, etc., are the common imaging tests recommended for staging once the colon cancer diagnosis is confirmed. These tests provide clearer images of the internal organs, which is necessary to obtain crucial information, such as the tumour size, the exact location of the tumour, regions where the disease has spread, etc. These imaging tests also help in treatment planning, therapy monitoring and restaging the disease during the treatment.
Treatment
The treatment planning for colon cancer cases is made based on various factors, which include the stage of the disease, the tumour grade, the patient’s age and his/her overall condition.
Early-stage colon cancers are usually treated with surgery; however, as the disease progresses, more comprehensive treatment plans are required which may include chemotherapy, radiation therapy, immunotherapy and targeted therapy.
a. Surgery: Surgery is the main line of treatment for colon cancers. The treatment plan for both early-stage and advanced-stage cancers include surgery in most cases. Depending on the disease stage, one of the following surgical procedures may be recommended by the doctor:
- Polypectomy: Early-stage colon cancers, where the tumour size is small and the disease is localised and contained within a polyp, the doctor may recommend a polypectomy, where that particular polyp is removed. This procedure could be done during the colonoscopy only.
- Endoscopic Mucosal Resection: This surgical procedure is also recommended for early-stage colon cancers. During this procedure, specialised tools are used to remove the cancerous polyp along with a portion of the inner lining of the large intestine. This is a minimally invasive procedure.
- Laparoscopic Surgery: Those cancerous polyps that cannot be removed during colonoscopy may be treated with laparoscopic surgery. During this procedure, the surgeon makes tiny incisions in the abdominal wall and specialised instruments along with a camera are introduced through these incisions to remove the tumour with the help of a video monitor. The surgeon may also collect lymph node samples during this procedure in order to check if cancer has spread to nearby regions.
- Partial Colectomy: As the disease progresses, a more complex surgical procedure is required for the management of colon cancers. During a partial colectomy, the part of the large intestine that contains the cancer is removed along with a small portion of healthy tissue called the margin. Post colectomy, the healthy portion of the colon is reconnected back with the rectum. In most cases, this is a minimally-invasive procedure.
- Surgery to Expel Faecal Matter: In a few cases, the healthy portion of the colon cannot be reconnected with the rectum, and in such cases, the doctor recommends an ostomy. An ostomy is a surgical procedure that connects the healthy portion of the colon to a newly-created opening on the abdominal wall, and this opening is called a stoma. This procedure helps in expelling the solid waste and gas from the body without the involvement of the rectum. The waste from the colon is collected in a collection bag, which is worn outside the body and it has to be cleaned and changed regularly as recommended by the doctor. In a few cases, the colostomy is temporary, until the large intestine and rectum regions heal after the surgery. However, it could also be permanent in some cases.
- Lymph Node Removal: During this procedure, the lymph nodes that are close to the tumour are removed and tested for the presence of cancer cells.
b. Radiation Therapy: In order to get rid of residual cancer cells, radiation therapy is recommended after the surgery. During this procedure, intense radiation beams are used to destroy the cancer cells. Since it is a non-invasive procedure, one can receive radiation therapy as an outpatient.
In patients with advanced-stage colon cancers, radiation therapy may be recommended to shrink the tumour and relieve pain and other symptoms caused by cancer.
c. Chemotherapy: During chemotherapy, strong anticancer drugs are used to destroy the cancer cells. As a systemic therapy, this treatment approach destroys cancer cells throughout the body. Chemotherapy may be administered before the surgery in order to shrink the tumour or after the surgery to kill the residual cancer cells.
Chemotherapy may also be given as a part of palliative therapy in order to delay the disease progression and ease the symptoms that are caused by the disease.
d. Immunotherapy: Specific proteins released by the colon cancer cells blind the immune cells, and this stops them from attacking the cancer cells and controlling the cancer growth. Immunotherapy aims at stimulating the body’s immune system to fight against cancer. Immunotherapy is usually recommended for patients with advanced-stage colon cancers.
e. Targeted Therapy: While administering targeted therapy, specific pathways are used by cancer cells to grow, divide and spread to nearby organs. The targeted therapy drugs block these pathways and cease cancer growth. This is not the main line of treatment for colon cancer, and it is recommended only in the advanced stages when the cancer is not responding to any other treatments.
Frequently Asked Questions
1. Are colon cancers treatable?
Yes, colon cancers are highly treatable, and in most cases, we can treat them with excellent survival rates without compromising the quality of life for the patients. Today, we have a myriad of treatment options available, which have fewer treatment complications for patients.
Just like any cancer, for colon cancer to be treated successfully, it has to be caught in its early stage, and screening is one way to detect colon cancers in the early stage.
High-risk individuals, i.e., those with obesity, having a sedentary lifestyle, having a positive family history or a personal history of polyps, etc., should consider regular colon cancer screening as this helps in early detection and timely treatment.
2. Do certain foods increase colon cancer risk?
Yes, researchers have found that increased consumption of certain foods can increase colon cancer risk. Keeping an eye on the intake of the following foods helps in reducing your colon cancer risk:
- Red meat – beef, goat, lamb and mutton, pork
- Processed meats – sausages, bacon, ham, canned meat, etc.
- Processed carbohydrates – food items made out of white flour, added artificial sweeteners and sugars, etc.
- Sugary beverages
3. Why is colon cancer becoming more common among the younger population?
Unfortunately, colon cancer incidence is increasing among the younger population, and there are many reasons for this. Key reasons for this trend include consumption of a low-fibre diet, processed foods, obesity caused due to inactive lifestyle, etc.
4. Can colon cancer be treated successfully with robotic surgery?
Robot-assisted surgery is one of the treatment options for colon cancer. Key benefits of robotic surgery include reduced pain and blood loss, shorter hospital stays, fewer treatment-related complications and faster recovery. However, not all colon cancer cases can be treated with robotic surgery.
While planning the treatment, the doctors take various factors like stage of the disease, exact location of the tumour, its grade, the patient’s age and his/her overall condition into account. During this assessment, if the doctor finds the patient to be the right candidate for robotic surgery, it will be included in his/her treatment plan.
5. Can I prevent colon cancer?
Although there is no measure that 100% prevent colon cancer, there are a few measures that you can take in order to reduce your colon cancer risk:
a. Have Healthy Food Habits: Your diet should include vegetables and whole grains, along with essential micronutrients, namely vitamins, minerals and antioxidants, as these are necessary for the healthy functioning of the large intestine.
b. Quit Tobacco: Never start smoking and if you already do, quit smoking as tobacco is associated with increased colon cancer risk.
c. Reduce Alcohol Consumption: Reduce your alcohol consumption as it helps in reducing your colon cancer risk.
d. Maintain Healthy Weight: Being overweight or obese can increase your colon cancer risk, and therefore, maintaining a healthy weight is necessary to reduce your colon cancer risk.
e. Consider Regular Screening: Consider regular screening for colon cancer. Ideally, you should start your colon cancer screening once you turn 45; this becomes especially important if you have a family history of the disease.