Colorectal cancer is cancer that grows in the large intestine (colon) or at the very bottom of the large intestine that connects to the anus (rectum).Colorectal cancer can be called colon cancer or rectal cancer, depending on where the cancer grows.
Colorectal cancer usually starts from colon polyps or tissue that grows abnormally on the inner wall of the colon or rectum. However, not all polyps develop into cancer. The likelihood of polyps turning into cancer depends on the type of polyp itself.
The following are three types of polyps that can grow in the large intestine:
- Polyp adenoma, which is a type of polyp that sometimes turns into cancer (a precancerous condition)
- Hyperplastic polyps, which are more common but generally do not become cancerous
- Sessile serrated polyps (CNS) and traditional serrated adenomas (TSA), which is a type of polyp that is considered an adenoma polyp, because of the high risk of turning into colorectal cancer
Regardless of the type of polyp, there are several factors that can increase the chances of a polyp turning into colorectal cancer, including:
- Polyp size larger than 1 cm
- More than 2 polyps in the colon or rectum
- Polyps grow on abnormal tissue (dysplasia), usually seen after the polyp is removed
Colorectal Cancer Causes and Risk Factors
Like all types of cancer, colorectal cancer occurs when cells in the body grow abnormally and form tumors. Over time, these tumors will grow and damage the surrounding healthy tissue.
It is not known exactly what causes these cells to grow uncontrollably. However, there are factors that can increase a person's risk of developing colorectal cancer, including:
- Aged 50 years or older
- Have a history of cancer or colorectal polyps
- Have a family who has had colorectal cancer or polyps
- Have a family history of colorectal cancer or breast cancer under the age of 50
- Have inflammatory bowel disease, both ulcerative colitis and Crohn's disease
- Suffering from diabetes
- Suffering from obesity or overweight
- Living an unhealthy lifestyle, for example, rarely consuming fiber and fruits, lack of exercise, and having a habit of smoking and consuming alcoholic beverages
- Undergoing radiotherapy (radiation therapy) in the abdominal area
Symptoms of Colorectal Cancer
Colorectal cancer usually only causes symptoms when the cancer cells are already growing. Symptoms vary, depending on the size and location of the cancer.
Some of the symptoms of colorectal cancer that can appear are:
- Diarrhea
- Constipation
- Defecation feels incomplete
- Losing weight for no apparent reason
- Bleeding in the rectum (the end of the large intestine)
- Bloody stools
- Nauseous
- Throw up
- Stomach pain, cramping, or bloating
- Body tired easily
When to go to the doctor
Colorectal cancer often causes no symptoms if it is still in its early stages. Therefore, consult with your doctor about the need for colorectal cancer screening, especially if you are at risk for colorectal cancer.
People over the age of 45 are advised to undergo regular colorectal cancer screening. However, first discuss with your doctor about the right type of screening and the screening schedule.
Colorectal Cancer Diagnosis
Colorectal cancer can be detected as early as possible through screening. That way, the chances of recovering from this disease are even greater. There are several types of screening for colorectal cancer, namely:
- Stool examination
Stool examination, which includes occult blood tests and detection of cancer cells in stool, can be done to detect colorectal cancer early. Depending on the type, your doctor may recommend that you get screened every 1-3 years.
- Sigmoidoscopy
Sigmoidoscopy is performed by inserting a thin tube with a camera (sigmoidoscope) from the anus into the lower part of the colon. This test is done every 5-10 years, accompanied by a occult blood test every year.
- Colonoscopy
The procedure for a colonoscopy is almost the same as a sigmoidoscopy. The difference is that the tube used for colonoscopy is longer. This procedure is recommended to be done every 10 years.
- Virtual colonoscopy (CT colonography)
A virtual colonoscopy is performed using a CT scan machine. This test displays an image of the colon as a whole for analysis. Virtual colonoscopy is recommended every 5 years.
In patients who show symptoms of colorectal cancer, the doctor will perform the following tests:
- Colonoscopy
A colonoscopy is performed to examine the entire rectum and colon. If an abnormality is suspected in the rectum or colon area, the doctor will perform a biopsy (tissue sampling) in the area, for later analysis in the laboratory.
- Examination of the tumor in the biopsy tissue
This examination aims to detect genes, proteins, or other substances associated with tumor cells. This test can help the doctor determine the method of treatment that will be carried out.
- blood test
A blood test is done to count the level of red blood cells, to determine whether there is bleeding in the rectum or colon. Blood tests are also done to calculate levels of carcinoembryonic antigen (CEA), which can be a sign of the stage of cancer progression.
- Scan
Scans can be done with ultrasound, CT scan, PET scan, or MRI, to see the location and size of cancer cells, and whether the cancer has spread to other organs.
Colorectal Cancer Stage
After the patient is diagnosed with colorectal cancer, the doctor will perform additional tests to determine the severity (stage) of the cancer. Colorectal cancer stages are divided into four, namely:
- Stage 0 Cancer appears on the surface of the inner wall of the rectum or colon, also known as carcinoma in situ
- Stage 1 Cancer has penetrated to the muscle layer of the colon or rectum, but has not spread beyond the colonic wall
- Stage 2 Cancer has spread to the colon wall, outside the colon wall, or to other nearby organs, but has not spread to the lymph nodes
- Stage 3 The cancer has spread beyond the walls of the colon and to one or more lymph nodes
- Stage 4 – the cancer has penetrated the colonic wall and spread to distant organs from the large intestine, such as the liver or lungs, with tumors varying in size
Colorectal Cancer Treatment
Colorectal cancer treatment depends on the patient's health condition, as well as the location and stage of the cancer. The following are some methods of colorectal cancer treatment:
Operation
Surgery is the main method of treating colorectal cancer. There are several types of surgery that doctors can choose, namely:
- Polypectomy, to remove small colorectal polyps through a colonoscopy procedure
- Endoscopic mucosal resection, to remove colorectal polyps and the inner lining of the large intestine, through a colonoscopy
- Laparoscopic surgery, to remove polyps that cannot be treated by colonoscopy
- Partial colectomy, to cut the part of the colon that is affected by cancer, along with some of the healthy tissue around it
In patients who undergo the removal of the colon or rectum affected by cancer, the doctor will perform an anastomosis, which is the union of each end of the digestive tract that has been cut by means of stitches.
If only a small portion of the healthy colon remains and it is impossible to connect, the doctor will make a hole in the abdominal wall for the passage of stool (colostomy) and attach a pouch to the outside of the abdominal wall. The patient's stool will come out through the stoma and be accommodated in a bag that is attached.
A colostomy can be temporary or permanent. A temporary colostomy is performed until the excised colon has healed. A permanent colostomy is performed on patients who have undergone complete rectal removal.
Surgical removal of colorectal cancer may be followed by surgical removal of the lymph nodes, to see if they have cancer.
Chemotherapy
Chemotherapy is the administration of drugs to kill or destroy cancer cells. Chemotherapy may be given before surgery to reduce the size of the cancer so that it can be easily removed. In addition, chemotherapy can also be done after surgery to reduce the risk of colorectal cancer coming back.
Doctors can prescribe a single drug or a combination of drugs, such as: fluorouracil, capecitabine, and oxaliplatin. If needed, doctors can combine chemotherapy drugs with targeted therapy.
Target therapy
Targeted therapy is the administration of drugs that specifically target genes, proteins, or body tissues that contribute to the development of cancer cells. Drugs used in targeted therapy work to inhibit the growth of cancer cells and prevent further damage to healthy cells.
Drugs used in targeted therapy can be either a single drug or a combination. Types of drugs include: bevacizumab, regorafenib, and cetuximab.
Immunotherapy
Immunotherapy is the administration of drugs that stimulate the body's immune system to fight cancer cells. This therapy is usually aimed at patients with advanced colorectal cancer.
Immunotherapy works in two ways:
- Drugs that encourage the immune system to attack cancer cells more effectively
- Drugs containing artificial compounds, which mimic how the immune system works
Radiotherapy
Radiotherapy or radiation therapy is a treatment that uses X-rays or protons to kill cancer cells. Radiotherapy can be done by shooting a beam of radiation from a radiotherapy machine at the cancer site, or by placing radioactive material into the patient's body (brachytherapy).
Radiotherapy can be done before surgery to shrink the size of the cancer, or after surgery to destroy any cancer cells that may have remained. If needed, radiotherapy can be combined with chemotherapy.
Ablation
Ablation is used to destroy cancer that has spread to the liver or lungs and is less than 4 cm in diameter. There are four ablation techniques that can be used to treat colorectal cancer, namely:
- Radiofrequency ablation, which is an ablation technique using high-frequency radio waves
- Microwave ablation, which is an ablation technique by utilizing the high temperature of electromagnetic microwaves
- Ethanol ablation, which is an ablation technique that is done by injecting alcohol right into the tumor area, using the help of ultrasound or CT scan
- Cryosurgery or cryotherapy, which is an ablation technique performed by freezing the tumor, using liquid nitrogen
Embolization
Embolization is used to destroy colorectal cancer that has spread to the liver and is more than 5 cm in diameter. This technique aims to block the liver arteries that provide nutrients and oxygen to the cancer. Embolization can be done in three ways, namely:
- Arterial embolization, which is performed by inserting an artery-clogging agent through a catheter
- Chemoembolization, which is performed by combining arterial embolization with chemotherapy
- Radioembolization, which is performed by combining arterial embolization with radiotherapy
Colorectal Cancer Complications
Colorectal cancer can cause a number of serious complications if not treated properly. These complications include:
- Colon blockage (bowel obstruction)
- The growth of new colorectal cancer in a different location
- Cancer spreads to other tissues or organs (metastatic)
Colorectal Cancer Prevention
It is not known how to prevent colorectal cancer. However, you can reduce your risk of developing colorectal cancer by doing the following:
- Eat whole grains, fruit and vegetables
- Exercise regularly, at least 30 minutes a day
- Reduce intake of fatty foods and fast food
- Stop smoking and consuming alcoholic beverages
- Maintain ideal body weight
- Manage diabetes well (if any)