Colorectal cancer, also known as bowel cancer, colon cancer, or rectal cancer, is any cancer that affects the colon and the rectum.
The possible risk factors include:
- older age
- a diet that is high in animal protein, saturated fats, and calories
- a diet that is low in fiber
- high alcohol consumption
- having had breast, ovary, or uterine cancer
- a family history of colorectal cancer
- having ulcerative colitis, Crohn’s disease, or irritable bowel disease (IBD)
- overweight and obesity
- a lack of physical activity
- the presence of polyps in the colon or rectum, as these may eventually become cancerous.
Most colon cancers develop within polyps (adenoma). These are often found inside the bowel wall.
Eating red or processed meats may increase the risk
People who have a tumor suppressor gene known as Sprouty2 may have a higher risk of some colorectal cancers.
According to WHO (World Health Organization) colorectal cancer is the second most common tumor among both men and women, after lung tumors.
Around 2 percent of people aged over 50 years will eventually develop colorectal cancer in Western Europe.
Colorectal cancer tends to affect men and women equally. However, men tend to develop it at a younger age.
Diagnosis of Colorectal Cancer:
The following are the most common screening and diagnostic procedures for colorectal cancer.
Fecal occult blood test (blood stool test)
This checks a sample of the patient’s stool (feces) for the presence of blood. This can be done at the doctor’s office or with a kit at home. The sample is returned to the doctor’s office, and it is sent to a laboratory.A blood stool test is not 100-percent accurate, because not all cancers cause a loss of blood, or they may not bleed all the time. Therefore, this test can give a false negative result.
Stool DNA test
This test analyzes several DNA markers that colon cancers or precancerous polyps cells shed into the stool. Patients may be given a kit with instructions on how to collect a stool sample at home. It is then sent to a laboratory.This test is more accurate for detecting colon cancer than polyps, but it cannot detect all DNA mutations that indicate that a tumor is present.
The doctor uses a sigmoidoscope, a flexible, slender and lighted tube, to examine the patient’s rectum and sigmoid. The sigmoid colon is the last part of the colon, before the rectum.
The test takes a few minutes and is not painful, but it might be uncomfortable. There is a small risk of perforation of the colon wall.
If the doctor detects polyps or colon cancer, a colonoscopy can then be used to examine the entire colon and take out any polyps that are present. These will be examined under a microscope.
A sigmoidoscopy will only detect polyps or cancer in the end third of the colon and the rectum. It will not detect a problem in any other part of the digestive tract.
Barium enema X-ray
Barium is a contrast dye that is placed into the patient’s bowel in an enema form, and it shows up on an X-ray. In a double-contrast barium enema, air is added as well.
The barium fills and coats the lining of the bowel, creating a clear image of the rectum, colon, and occasionally of a small part of the patient’s small intestine.
A flexible sigmoidoscopy may be done to detect any small polyps the barium enema X-ray may miss. If the barium enema X-ray detects anything abnormal, the doctor may recommend a colonoscopy.
A colonoscope is longer than a sigmoidoscope. It is a long, flexible, slender tube, attached to a video camera and monitor. The doctor can see the whole of the colon and rectum. Any polyps discovered during this exam can be removed during the procedure, and sometimes tissue samples, or biopsies, are taken instead.
A colonoscopy is painless, but some patients are given a mild sedative to calm them down. Before the exam, they may be given laxative fluid to clean out the colon. An enema is rarely used. Bleeding and perforation of the colon wall are possible complications, but extremely rare.
A CT machine takes images of the colon, after clearing the colon. If anything abnormal is detected, conventional colonoscopy may be necessary. This procedure may offer patients at increased risk of colorectal cancer an alternative to colonoscopy that is less-invasive, better-tolerated, and with good diagnostic accuracy.
Ultrasound or MRI scans can help show if the cancer has spread to another part of the body.
The Centers for Disease Control and Prevention (CDC) recommend regular screening for those aged 50 to 75 years. The frequency depends on the type of test.
A commonly used system gives the stages a number from 0 to 4. The stages of colon cancer are:
- Stage 0: This is the earliest stage, when the cancer is still within the mucosa, or inner layer, of the colon or rectum. It is also called carcinoma in situ.
- Stage 1: The cancer has grown through the inner layer of the colon or rectum but has not yet spread beyond the wall of the rectum or colon.
- Stage 2: The cancer has grown through or into the wall of the colon or rectum, but it has not yet reached the nearby lymph nodes.
- Stage 3: The cancer has invaded the nearby lymph nodes, but it has not yet affected other parts of the body.
- Stage 4: The cancer has spread to other parts of the body, including other organs, such as the liver, the membrane lining the abdominal cavity, the lung, or the ovaries.
- Recurrent: The cancer has returned after treatment. It may come back and affect the rectum, colon, or another part of the body.
Treatment will depend on several factors, including the size, location, and stage of the cancer, whether or not it is recurrent, and the current overall state of health of the patient.
Treatment options include chemotherapy, radiotherapy, and surgery.
Surgery for colorectal cancer
This is the most common treatment. The affected malignant tumors and any nearby lymph nodes will be removed, to reduce the risk of the cancer spreading.
The bowel is usually sewn back together, but sometimes the rectum is removed completely and a colostomy bag is attached for drainage. The colostomy bag collects stools. This is usually a temporary measure, but it may be permanent if it is not possible to join up the ends of the bowel.
If the cancer is diagnosed early enough, surgery may successfully remove it. If surgery does not stop the cancer, it will ease the symptoms.
Chemotherapy involves using a medicine or chemical to destroy the cancerous cells. It is commonly used for colon cancer treatment. Before surgery, it may help shrink the tumor.
Targeted therapy is a kind of chemotherapy that specifically targets the proteins that encourage the development of some cancers. They may have fewer side effects than other types of chemotherapy. Drugs that may be used for colorectal cancer include bevacizumab (Avastin) and ramucirumab (Cyramza).
A study has found that patients with advanced colon cancer who receive chemotherapy and who have a family history of colorectal cancer have a significantly lower likelihood of cancer recurrence and death.
Radiation therapy uses high energy radiation beams to destroy the cancer cells and to prevent them from multiplying. This is more commonly used for rectal cancer treatment. It may be used before surgery in an attempt to shrink the tumor.
Both radiation therapy and chemotherapy may be given after surgery to help lower the chances of recurrence