Table Of Content
Introduction
The large intestine is a component of the gastrointestinal (GI) tract or digestive system. It is composed of the colon and the rectum, which play a vital role in the body's ability to process waste. The first five to six feet of the large intestine are made up of the colon, and the last six inches are made by the rectum, which ends at the anus.
Cancer that begins in the colon is known as colon cancer, while cancer that begins in the rectum is known as rectal cancer. Cancers that affect both of these organs are otherwise known as colorectal cancer. It happens when the cells lining the colon or rectum become abnormal and grow out of control.
Types Of Colorectal Cancer
Adenocarcinoma is the most prevalent type of colon and rectum cancer. These tumors start in the cells that make mucus lubricate the inside of the colon and rectum.
Gastrointestinal Stromal Tumors (GIST) begin in the special cells found in the lining of the gastrointestinal tract called interstitial cells of Cajal (ICCs). It can be benign (non-cancerous) at first, but many of them progress to malignancy.
Primary colorectal lymphomas develop in the lymphocytes or immune system cells. Lymphoma may develop in many parts, including the bone marrow, lymph nodes, spleen, thymus, and digestive tract. It is relatively rare and is more common in men.
Carcinoid tumors start in nerve cells called neuroendocrine cells, which help to regulate hormone production. These tumors are a group of cancers called neuroendocrine tumors (NETs). It is slow-growing and may develop in the gastrointestinal tract or lungs.
Colorectal squamous cell carcinoma occurs when squamous cells in the colorectal epithelium start growing uncontrollably and become cancerous.
Colon and rectal melanomas start to develop anywhere in our body, including in the colon and rectum, and may spread to the gastrointestinal tract (GI tract) from the primary melanoma site.
Stages Of Colorectal Cancer
The TNM staging tool is the common tool used in determining the stages of colorectal cancer.
- Stage 0: It is an early stage of cancer known as cancer in situ or intramucosal carcinoma. These cancer cells are present only in the mucosa or the inner lining of the colon or rectum.
- Stage I: This tumor has invaded the muscle layer of the colon or rectum. It has grown through the mucosa and has not metastasized to nearby lymph nodes or distant body parts.
- Stage II A: The tumor has grown into the outermost layers of the rectum or colon but has not invaded nearby lymph nodes, tissue, or distant body parts.
- Stage II B: The tumor has grown through the layers of the muscle to the abdomen lining, known as the visceral peritoneum. It has not invaded the nearby lymph nodes or distant sites.
- Stage II C: Cancer has spread through the colon or rectum's wall, grown into nearby tissues or organs, and has not spread to the neighboring lymph nodes or distant sites.
- Stage IV A: The tumor may or may not grow through the colon or rectum wall. It may not spread to nearby lymph nodes and invade a single distant body part, such as the liver or lungs.
- Stage IV B: The tumor may or may not grow through the colon or rectum wall. It may not spread to neighboring lymph nodes but spread to more than one distant body part.
- Stage IV C: The tumor may or may not grow through the wall of the colon or rectum. It may not have spread to nearby lymph nodes but spread to the peritoneum and other sites or organs.
Symptoms Of Colorectal Cancer
- Changes in bowel habits
- Diarrhea and constipation
- Feeling that bowel does not empty
- Unexplained weight loss
- Bright or very dark blood in the stool
- Abdominal pain and bloating
- Anemia (low number of blood cells)
- Fatigue or tiredness
Causes and Risk Factors Of Colorectal Cancer
Colorectal cancers develop due to genetic mutations in the DNA of the cells in the colon and rectum that make them unable to control their growth and division. These mutant cells may die or attack the immune system. However, some mutated cells may escape the immune system that grows and proliferate out of control, forming a colon or rectum tumor. It is not known what exactly causes colorectal cancer. The various risk factors of colorectal cancer include:
Age: Colorectal cancer can occur at any age, but people older than 50 are more prone to develop colorectal cancer.
Gender: Men have a higher risk of acquiring colorectal cancer than women.
Race: The risk of colorectal cancer is most commonly occurring in black people than in white people.
Overweight and obesity: Being obese or overweight raises the risk of developing colorectal cancer.
Lack of physical activity: People with insufficient physical activity are at possible risk of getting colorectal cancer.
Diet: Consuming a lot of red and processed meat increases the disease risk. A high-fat and calorie diet with less fiber intake also increases the risk of colorectal cancer.
Smoking and alcohol consumption: People with regular smoking and heavy alcohol drinking habits are more likely to develop the risk of colorectal cancer.
Personal history of cancer: People with a previous personal history of colorectal cancer are more prone to its recurrence, and those diagnosed with ovarian or uterine cancer are more chance of developing colorectal cancer.
Family history: If anyone in your family members has colorectal cancer, the risk of developing this disease is higher.
Inflammatory bowel disease (IBD): People with Inflammatory bowel disease, like Crohn's disease ulcerative colitis, may develop chronic inflammation of the large intestine, which increases the colorectal cancer risk.
Adenomatous polyps (adenomas): Polyps are not the tumor, but some kind of polyps called adenomas can develop into colorectal cancer. People who already have adenomas are at a greater risk of developing more polyps and colorectal cancer.
Type 2 diabetes: The risk of colorectal cancer is higher in people with type 2 diabetes, which is usually not insulin dependent.
Genetic conditions: Some inherited genetic conditions may raise the risk of colorectal cancer. Those includes:
- Lynch syndrome is mainly caused by an inherited defect in the MLH1, MSH2, or MSH6 genes, as well as alterations in other genes. Normally, these genes help in the
repair of DNA damage. This syndrome is otherwise known as hereditary nonpolyposis colorectal cancer (HNPCC). - Familial adenomatous polyposis (FAP) is caused by changes in the APC gene that a person inherits from their parents. People with FAP are also more likely to develop stomach cancer, small intestine cancer, pancreas cancer, liver cancer, and other organ cancers.
- Peutz-Jeghers syndrome (PJS) is caused by changes in the STK11 (LKB1) gene. This genetic condition causes freckles around the mouth and increases the chance of colorectal cancer.
- MUTYH-associated polyposis (MAP): MUTYH gene encodes an enzyme called DNA glycosylase, which is involved in DNA repair. Myth-associated polyposis raises the risk of colorectal, GI (gastrointestinal) tract, and thyroid cancer.
Colorectal Cancer Screening
Screening tests are performed when you are healthy and have no signs or symptoms of the disease, and they can help in the early detection of cancer, so that appropriate treatment can begin. The following tests are used to screen colorectal cancer.
A colonoscopy allows a physician to examine the whole rectum and colon of a sedated patient. A colonoscope (a flexible, lighted tube) is introduced into the rectum, and the entire colon is examined for cancer or polyps. During this procedure, a physician can remove polyps or other tissue to check for cancerous symptoms.
Virtual colonoscopy is also known as CT colonography or computed tomography colonography. During this procedure, a CT scan creates cross-sectional images of the abdominal organs, allowing the physician to detect abnormalities in the rectum and colon. A tiny tube (catheter) is inserted into your rectum to fill the colon with air or carbon dioxide to create clear images.
A sigmoidoscopy is used to look for polyps, cancer, and other abnormalities where the flexible, lighted tube is placed into the rectum and lower colon. These screening tests remove the polyps that can prevent colorectal cancer.
A fecal occult blood test (FOBT) is used to detect stool samples in the blood, which can be signs of polyps or cancer. Blood in the stool indicates colorectal cancer or another medical condition, including polyps or ulcers.
The double contrast barium enema (DCBE) employs an enema containing barium, which helps to display the colon and rectum on x-rays. The colon and rectum are then imaged using x-rays. In general, most physicians would prescribe additional screening procedures because a barium enema is less probable than a colonoscopy, sigmoidoscopy, or CT colonography to find precancerous polyps.
Stool DNA tests examine the DNA from a person's feces sample to check for cancer. It uses DNA changes that occur in polyps and cancers to find out if a colonoscopy should be done.
Colorectal Cancer Diagnosis
Medical history and physical examination: The medical professional will ask you for your complete medical and family history and will perform a detailed physical examination. He examines your abdomen (belly) for masses or enlarged organs to assess the possible risk factors, symptoms, or any other health issue you have.
Biopsy: Medical professional removes a small amount of tissue for examination under a microscope. It is the most accurate method for diagnosing colorectal cancer.
Diagnostic colonoscopy: It is used to examine the entire colon and rectum by inserting a colonoscope (thin, flexible, and lighted tube with a camera) through the anus and into the colon and rectum. Polyps can be removed during this procedure to check for cancer symptoms.
Blood tests: Your physician may perform a blood test to detect whether you have colorectal cancer. The types of blood tests include:
- Complete blood count (CBC): This test is performed to detect the different types of cells in your blood and detect if you have anemia (lack of red blood cells). People with colorectal cancer may get anemia as this tumor has been bleeding for a long time.
- Liver enzymes: Colorectal cancer can spread to the liver. So, you might also undergo a blood test to detect how well your liver is functioning.
- Tumor markers: Colorectal cancer cells can produce tumor markers, which are substances present in the blood. Carcinoembryonic antigen is the most prevalent tumor marker for colorectal cancer (CEA). High levels of CEA could be a sign that cancer has spread to different body areas.
Imaging tests: Various imaging tests are performed to diagnose colorectal cancer. Those are:
- Chest x-rays provide images of the structures inside the body by using a small amount of radiation. If more detailed images are required, the doctor may recommend a chest x-ray. It is used to detect whether cancer has spread to other organs like the lungs.
- Computed tomography (CT) scan uses x-ray machines and computers to create more detailed images of your body. CT scans are performed to investigate the extent of cancer spread to nearby lymph nodes or to your liver, lungs, or other organs.
- Ultrasound involves using sound waves to create an image of the organs inside your body. Endorectal ultrasound is commonly used to determine how rectal cancer has grown and used to plan treatment. It can help to examine whether cancer has spread to surrounding lymph nodes or beyond the pelvis.
- Magnetic resonance imaging (MRI) scan involves using magnetic fields to create more detailed pictures of the body. It measures the tumor size and detects where colorectal cancer has grown.
- A Positron emission tomography (PET) scan creates images of the inside organs and tissues in your body. Radioactive glucose is injected into the patient's vein, and this sugar substance is absorbed by the cells with the greatest energy expansion. Because cancer uses energy actively, it absorbs more radioactive material. The PET scanner identifies this substance, producing images of the inside of the body.
Colorectal Cancer Treatment
The doctor may recommend treatment options depending on the individual's age, type and stage of colorectal cancer, possible side effects, and overall health. The major treatment types for colorectal cancer include surgery, chemotherapy, radiation therapy, targeted therapy, and immunotherapy.
Surgery is the most commonly used treatment for colorectal cancer. It involves the removal of the tumor and nearby healthy tissue during an operation, otherwise known as surgical resection. This method removes a part of the healthy colon and rectum, and lymph nodes. Types of surgery used in colorectal cancer include:
- Local excision: If the cancer is determined at a very early stage, the physician inserts a tube into the colon and rectum through the cutting tool to remove the cancer; this is called a local excision. If the cancer is detected in a polyp, the operation is called a polypectomy.
- Resection: If the cancer is large, the physician will remove the tumor and healthy tissue around it, called a partial colectomy. Then he removes the segment of the colon that contains cancer and some nearby healthy tissue and connects the remaining tissue.
- Radiofrequency ablation: It kills cancer cells using a specific probe with small electrodes. Only local anesthetic is required when the probe is inserted directly through the skin. In other cases, the probe is inserted via an abdominal incision under general anesthesia in the hospital.
- Cryosurgery: It is a treatment in which abnormal tissue is frozen and destroyed using an instrument, otherwise known as cryotherapy.
- Colostomy: If the surgeon cannot rejoin the colon's two ends, a stoma (an opening) is created outside the body to allow waste to pass through. It is known as a colostomy.
Chemotherapy treatment involves using drugs to kill cancer cells or prevent them from proliferating by stopping the growth of cancer cells. It is typically given after surgery whether the cancer is larger or has spread to lymph nodes. It has the following sub-types:
- Systemic chemotherapy: Chemotherapy medications can enter the bloodstream and reach cancer cells throughout the body when orally taken or injected into a muscle or vein. It is known as systemic chemotherapy.
- Regional chemotherapy: It refers to the administration of chemotherapy that targets cancer cells primarily in the cerebrospinal fluid or a body cavity, including the abdomen.
Radiation therapy uses high-energy x-rays and protons to damage the DNA of cancer cells and shrink tumors, and prevent tumor cells from proliferating and spreading. It may be used in combination with chemotherapy and used to relieve symptoms.
Targeted therapy can identify and target the genes or proteins involved in cancer cell proliferation and multiplication by preventing cancer growth. Some targeted treatments are only effective in patients whose cancer cells have specific genetic mutations.
Immunotherapy uses our disease-fighting immune system to fight cancer, and it can identify and destroy any abnormal cells and prevent some cancerous growth. Advanced
colon cancer patients can benefit from immunotherapy treatments.
Palliative care is specialized care that helps to relieve pain and other symptoms associated with a serious illness. It enhances the cancer patient's quality of life. When palliative care is used along with other appropriate treatments, a cancer patient may feel better and live longer.
Colorectal Cancer Prognosis
Colorectal cancer prognosis depends upon various factors, such as
- Age
- Gender
- Stage and grade of cancer
- Diagnosis
- Lymph node involvement
- Colon blockage
- Carcinoembryonic antigen
- Patient's general and overall health
The survival rate of colorectal cancer is five years in patients who have been diagnosed early. It may differ from each of the following.
- Localized: 91%
- Regional: 72%
- Distant: 15%
9 Tips To Prevent Colorectal Cancer
- Get a regular screening
- Limit or avoid alcohol consumption
- Quit the smoking habit
- Be physically active and exercise regularly
- Maintain a healthy weight
- Eat a healthy balanced diet
- Limit red and processed meat
- Take vitamin D and calcium supplements
- Take a low dose of aspirin per day.
Colorectal Cancer FAQs
1. Who is more likely to get colorectal cancer?
People who are older than 50 are more prone to colorectal cancer. People who have personal or family history of cancer or polyps are at the greatest risk of colorectal cancer.
2. What kinds of diagnostic tests will I need?
A variety of diagnostic tests may help to determine the stage of your cancer, its types, and available treatment options. Biopsy, colonoscopy, blood tests, and imaging tests like chest x-ray, MRIs, PET scans, and ultrasounds. This diagnostic test may help to determine whether specific treatment options are available to you.
3. What are my risk factors for colorectal cancer?
The risk factors of colorectal cancer include:
- Age and gender
- Being Black
- Food or diet
- Overweight or obesity
- Family history
- Personal history of cancer
- Smoking and alcohol consumption
- Inflammatory bowel disease (IBD)
- Adenomatous polyps (adenomas)
- Type 2 diabetes
- Genetic conditions
4. What stage of colorectal cancer do I have?
There are five stages of colorectal cancer. Stage 0, the earliest stage, is used to define cancer confined to the large intestine's inner lining. Stage 4 is considered the most advanced stage, and cancer has metastasized or spread outside the colon to other body areas.
5. What are my colorectal cancer treatment options?
My colorectal cancer treatment options include surgery, chemotherapy, radiation therapy, targeted therapy, immunotherapy, and palliative therapy.
6. Is colorectal cancer curable?
Yes, Colorectal cancer can be a highly treatable and often curable disease when detected early. Surgery is the main form of treatment and results in a cure in approximately 50% of patients.
7. What symptoms might I observe if I have colorectal cancer?
Changes in bowel habits, diarrhea, constipation, feeling that the bowel does not empty fully, unexplained weight loss, bright red or very dark blood in the stool, abdominal pain and bloating, anemia (low number of blood cells), fatigue or tiredness are the symptoms of my colorectal cancer.
References
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