Overview
Colon cancer begins in the colon or rectum, which are part of the large intestine. The large intestine is the final section of the digestive system that helps break down food and absorb nutrients. Colon cancer often starts as small, benign polyps on the colon or rectum’s lining. Some of these polyps may become cancerous over time and spread to other parts of the body.
Type of cancer
· The most common type of colon cancer is adenocarcinoma, which is a cancer of the cells that line the inside surface of the colon or rectum. Adenocarcinomas account for 90 to 95 percent of all colorectal cancer cases . Adenocarcinomas usually start as small growths called polyps that form on the inner lining of the colon or rectum. Some of these polyps can become cancerous over time and spread to other parts of the body.
· There are also some rare types of colon cancer, such as:
o Carcinoid tumors, which start in hormone-producing cells in the intestines.
o Gastrointestinal stromal tumors, which can be a type of soft tissue sarcoma that can be found anywhere in the gastrointestinal tract but is rare in the colon.
o Lymphoma, which is a cancer of the immune system that can start in the colon.
o Melanoma, which is a type of skin cancer that can spread to the colon.
 
Stage
· Colon cancer can be categorized by how much it has spread:
o Localized (Stages 0-II): Confined to the primary (original) tumor.
o Regional (Stage III): Cancer that has spread to lymph nodes.
o Distant (Stage IV): Cancer that has spread to distant organs (metastasis) or stage IV.
· The stage of colon cancer is determined by examining the tissue removed during surgery, as well as by doing tests such as colonoscopy, biopsy, blood tests, and imaging tests. The stage of colon cancer affects the treatment options and the prognosis of the disease.
· The stages of colon cancer are as follows:
o Stage 0: The cancer is in its earliest stage. It has not grown beyond the inner layer (mucosa) of the colon or rectum. This stage is also known as carcinoma in situ or intramucosal carcinoma.
o Stage I: The cancer has grown into the innermost layer (or mucosa) to the next layer of the colon (the submucosa). It may have also grown into a muscular layer called the muscularis propria. It has not spread to the lymph nodes.
o Stage II: The cancer has grown beyond the mucosa and the submucosa. Stage II colon cancer is classified further as stage IIA, IIB, or IIC.
§ Stage IIA: The cancer has not spread to the lymph nodes or nearby tissue. It has reached the outer layers of the colon, but it has not completely grown through.
§ Stage IIB: The cancer has not spread to the lymph nodes, but it has grown through the outer layer of the colon and to the visceral peritoneum. This is the membrane that holds the abdominal organs in place.
§ Stage IIC: The cancer has not spread to the lymph nodes. But it has grown through the outer layer of the colon as well as to nearby organs or structures.
o Stage III: The cancer has spread to nearby lymph nodes, but not to distant organs. Stage III colon cancer is classified as stage IIIA, IIIB, or IIIC.
§ Stage IIIA: The tumor has grown to or through the muscular layers of the colon and is found in nearby lymph nodes. It has not spread to distant nodes or organs.
§ Stage IIIB: Colon cancer will be classified as stage IIIB in either of the following situations:
§ The cancer has grown through the outer layer of the colon and to the visceral peritoneum and is found in nearby lymph nodes.
§ The cancer has grown through the outer layer of the colon as well as to nearby organs or structures and is found in nearby lymph nodes.
§ Stage IIIC: The cancer has grown to or through the muscular layers of the colon and is found in four or more nearby lymph nodes. It has not spread to distant nodes or organs.
o Stage IV: The cancer has spread to distant organs, such as the liver or lungs, or to distant lymph nodes. Stage IV colon cancer is classified as stage IVA or IVB.
§ Stage IVA: The cancer has spread to one distant organ or set of distant lymph nodes.
§ Stage IVB: The cancer has spread to more than one distant organ or set of distant lymph nodes, or to the lining of the abdominal cavity (peritoneum)
 
 
Incidence Rates
· Colon cancer is the third most common cancer worldwide, accounting for approximately 10% of all cancer cases and is the second leading cause of cancer-related deaths worldwide.
· In 2020, more than 1.9 million new cases of colon cancer and more than 930,000 deaths due to colon cancer were estimated to have occurred worldwide.
· The incidence rates were highest in Europe and Australia and New Zealand, and the mortality rates were highest in Eastern Europe.
· By 2040, the burden of colon cancer will increase to 3.2 million new cases per year (an increase of 63%) and 1.6 million deaths per year (an increase of 73%).
· In Asia, the incidence and mortality rates of colon cancer vary by region and country. For both sexes, Eastern Asia has the highest incidence rate (male 50.4/100,000; female 19.2/100,000) whereas South-Central Asia has the lowest incidence rate (male 11.9/100,000; female 3.4/100,000).
· The incidence and mortality rates of early-onset colon cancer (diagnosed before age 50) are also increasing in many countries, especially in low- and middle-income countries.
Symptoms
· The symptoms of colon cancer are:
o Changes in bowel habits, such as diarrhea, constipation, or narrowing of the stool, that last for more than a few days .
o Rectal bleeding or blood in the stool, which may make the stool look dark or black .
o Abdominal pain, cramps, gas, or discomfort, especially if it occurs frequently or does not go away .
o A feeling of incomplete bowel emptying or a sensation of pressure in the rectum .
o Weakness, fatigue, or weight loss, which may be caused by anemia (low red blood cell count) or malnutrition due to poor absorption of nutrients .
o Nausea, vomiting, or jaundice (yellowing of the skin and eyes), which may indicate that the cancer has spread to the liver or other organs .
o Pelvic pain, which may indicate that the cancer has spread to the ovaries, uterus, or bladder.
· Many of these symptoms can also be caused by other conditions, such as infection, hemorrhoids, irritable bowel syndrome, or inflammatory bowel disease. Therefore, it is important to see a doctor if you have any of these symptoms for longer than a week or two. A doctor can perform tests, such as a colonoscopy, a biopsy, blood tests, and imaging tests, to diagnose colon cancer and determine its stage and type.
 
Cause
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· Some of the possible causes of colon cancer are:
o Changes in the DNA of the cells that line the inside of the colon or rectum. These changes can make the cells grow and divide abnormally, forming polyps that can become cancerous over time. Some of these changes are inherited from parents, while others are acquired during a person’s lifetime .
o Risk factors that can increase the chances of developing colon cancer, such as older age, black race, personal or family history of colorectal cancer or polyps, inherited genetic syndromes, such as Lynch syndrome or familial adenomatous polyposis, lifestyle factors, such as a diet high in processed meats and low in fruits and vegetables, physical inactivity, obesity, smoking, and heavy alcohol use .
o Inflammatory bowel disease, such as Crohn’s disease or ulcerative colitis, which causes chronic inflammation and ulcers in the colon or rectum .
o Type 2 diabetes, which affects how the body uses sugar and may increase the risk of colon cancer by affecting insulin levels, inflammation, and other factors .
 
Risk factors
Risk Factors for Colon Cancer:
1. Age: The risk of colon cancer increases with age. Most people diagnosed with colon cancer are over 50 years old.
2. Race: Black individuals have a higher risk of colon cancer compared to other races.
3. Family History: Having a close relative (parent, sibling, or child) who had colon cancer or polyps increases your risk. This risk is even higher if your relative was diagnosed before age 45 or if you have more than one affected relative.
4. Genetic Syndromes: Inherited genetic conditions like Lynch syndrome or familial adenomatous polyposis (FAP) can increase your risk. These syndromes cause many polyps to develop in your colon or rectum, some of which can become cancerous over time.
5. Lifestyle Factors: Certain habits or behaviors can affect your risk of colon cancer, such as:
o Lack of Physical Activity: Being inactive can lead to weight gain and increase your risk.
o Diet: Consuming a lot of red meat, processed meat, or fat, and not eating enough fruits, vegetables, or fiber can increase your risk.
o Obesity: Being overweight or obese, especially carrying extra fat around your waist, can raise your risk.
o Smoking: Tobacco use can damage cells in your colon and increase your risk.
o Alcohol: Excessive alcohol consumption can increase your risk, especially if you drink more than one drink per day for women or two drinks per day for men.
6. Inflammatory Bowel Disease: Chronic inflammation of your colon or rectum, such as Crohn’s disease or ulcerative colitis, can increase your risk.
7. Diabetes: Having type 2 diabetes can affect your body’s ability to use sugar and may increase your risk of colon cancer by affecting your insulin levels, inflammation, and other factors.
 
Diagnosis
Diagnosis of Colon Cancer:
1. Medical History and Physical Exam: Your doctor will inquire about your health history and any family history of disease to identify potential risk factors.
2. Digital Rectal Exam (DRE): The doctor will examine your rectum using a lubricated, gloved finger to detect any unusual areas.
3. Imaging Tests: Several imaging tests can help diagnose colorectal cancer, including:
o CT or CAT scan
o Ultrasound
o MRI scan
o Chest x-ray
o PET scan
o Angiography
4. Colonoscopy: This procedure involves using a camera-equipped, flexible tube to examine your entire colon and rectum.
5. Biopsy: The removal of tissue for lab testing, typically obtained during a colonoscopy, helps to diagnose colon cancer.
 
 
 
Test
Tests for Colon Cancer:
1. Stool Tests: These are used to find hidden (occult) blood, which can be a potential indicator of cancer. Stool-based tests are tests that check for blood or DNA changes in the stool that may indicate the presence of polyps or cancer. Stool-based tests include fecal occult blood test (FOBT), fecal immunochemical test (FIT), and stool DNA test (FIT-DNA). Stool-based tests are done at home and require collecting one or more samples of stool.  
2. Blood Tests: Your doctor may run these tests to see if you have colorectal cancer or to monitor the disease after diagnosis.
3. Complete Blood Count (CBC): This test assesses your blood cells and can indicate anemia, a condition common in long-term colorectal bleeding.
4. Liver Enzymes: A blood test to evaluate liver functions can confirm if cancer has spread to the liver.
5. Tumor Markers: The blood may contain tumor markers—substances made by cancer cells. The carcinoembryonic antigen (CEA) is a primary marker used to track colorectal cancer.
Treatment
Treatment for Colon Cancer:
1. Surgery: This is the primary treatment for most colon cancers. It involves removing the part of the colon containing the cancer, along with some surrounding normal tissue and nearby lymph nodes. The remaining parts of the colon are then reconnected or attached to an opening in the abdomen (a colostomy). Surgery can be performed through a large incision (open surgery) or several small incisions (laparoscopic or robotic surgery).
2. Chemotherapy: This involves using drugs to kill cancer cells or inhibit their growth. Chemotherapy can be administered before surgery (neoadjuvant chemotherapy) to shrink the tumor, making it easier to remove, or after surgery (adjuvant chemotherapy) to reduce the risk of cancer recurrence. It can also be used to treat advanced or metastatic colon cancer that has spread to other parts of the body.
3. Radiation Therapy: This involves using high-energy rays or particles to destroy cancer cells or slow their growth. While not often used for colon cancer, it may be administered before surgery to shrink the tumor, after surgery to eliminate any remaining cancer cells, or to alleviate symptoms such as pain or bleeding in advanced or metastatic colon cancer.
4. Targeted Therapy: This involves using drugs that target specific features of cancer cells, such as proteins or genes, that aid their growth and survival. Targeted therapy can be used alone or in combination with chemotherapy to treat advanced or metastatic colon cancer with certain gene mutations or biomarkers.
5. Immunotherapy: This involves using drugs that help the body’s immune system recognize and attack cancer cells. Immunotherapy can be used to treat advanced or metastatic colon cancer with certain gene mutations or biomarkers, such as mismatch repair deficiency (dMMR) or microsatellite instability-high (MSI-H).
The optimal treatment for colon cancer depends on various factors, including the stage and type of cancer, the patient’s age, general health, personal preferences, and the potential benefits and side effects of each treatment option. Patients should discuss their treatment options with their doctor and make an informed decision based on their individual situation.
 
Prognosis
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Prognosis for Colon Cancer Patients: The prognosis, or outlook, for colon cancer patients depends on several factors, including the type and stage of the cancer, the patient’s overall health, treatment options, and response to therapy. Other factors such as age, race, genetics, and lifestyle can also influence the prognosis. Understanding the prognosis can help patients and doctors make informed decisions about treatment and future planning.
One way to measure the prognosis for colon cancer patients is by looking at survival rates. These represent the percentage of people who survive a certain amount of time (usually 5 years) after being diagnosed with cancer. Survival rates are based on previous outcomes of large numbers of people who had the same type and stage of cancer, but they cannot predict what will happen in any individual case. Survival rates are also relative, meaning they compare the survival of people with cancer to the survival of people in the general population.
Here are some key facts and figures about survival rates for colon cancer:
1. Overall Survival Rates: For all colorectal cancer patients, regardless of cancer stage, the five-year relative survival rate is 64.4% for colon cancer and 67% for rectal cancer. This means that out of every 100 people diagnosed with colon cancer, 64 are expected to be alive five years after diagnosis.
2. Stage-Specific Survival Rates: For colon cancer, the overall 5-year relative survival rate is 63%. If the cancer is diagnosed at a localized stage, the survival rate is 91%. If the cancer has spread to surrounding tissues or organs and/or the regional lymph nodes, the survival rate is 72%. If the cancer has spread to distant parts of the body, the survival rate is 14%.
3. Age and Race Factors: The survival rates for colon cancer are higher for younger patients than for older patients. For example, the 5-year relative survival rate for people diagnosed with colon cancer before age 50 is 82%, while the rate for people diagnosed at age 65 or older is 58%. The survival rates for colon cancer are lower for black patients than for white patients. For example, the 5-year relative survival rate for black people diagnosed with colon cancer is 56%, while the rate for white people is 65%.
4. Cancer Characteristics: The survival rates for colon cancer can also vary by the type and characteristics of the cancer, such as the histology (the appearance of the cells under a microscope), the grade (how abnormal the cells look and how quickly they grow), the molecular features (such as gene mutations or biomarkers), and the response to treatment.
These statistics are general estimates and may not accurately predict an individual’s prognosis. Each person’s situation is unique, and the best course of action should be determined through discussions with their healthcare provider.
 
Supportive
Supportive Care for Colon Cancer Patients: Supportive care is a crucial part of the treatment process for colon cancer patients. It assists patients in managing the physical, practical, emotional, and spiritual challenges associated with colorectal cancer. Here are some key aspects of supportive care:
1. Self-Esteem and Body Image: Self-esteem refers to how a person feels about themselves, while body image is how a person perceives their own body.
2. Living with a Colostomy or Ileostomy: A colostomy involves creating a stoma, an artificial opening from the colon to the outside of the body through the abdominal wall.
3. Nutrition: Maintaining proper nutrition is vital for preserving strength and promoting recovery.
4. Questions to Ask About Supportive Care: Open and honest discussions with your healthcare team about your symptoms, side effects, and any changes in your body are essential.
Numerous programs and services are available to meet the needs and improve the quality of life of people living with cancer and their loved ones, especially after treatment has ended. Remember, each person’s situation is unique, and the best course of action should be determined through discussions with their healthcare provider.