Health Desk- Our digestive system digests food and absorbs nutrients from it. The esophagus (food pipe), stomach (stomach), small intestine, and large intestine make up the digestive system. The large intestine begins at the colon, which is about 5 feet long, and ends at the rectum and anus (anus).
The wall of the colon and rectum consists of four layers of tissue. Cancer occurs when cells in the body start growing uncontrollably. Colorectal cancer begins in the innermost layer of the wall of the large intestine. Most colorectal cancers begin with small polyps. These polyps are a group of cells. Over time, some of these polyps develop into cancer. This cancer spreads first to the wall of the large intestine, then to nearby lymph nodes, and then throughout the body.
Colon cancer and rectal cancer are very similar and are discussed together under the name of colorectal cancer. But the rectum is in a narrow space called the pelvis. Here it is attached to the surrounding organs and the pelvic bone. For this reason, the method of screening and diagnosis of rectal cancer is slightly different.
Most of these cancers are adenocarcinomas. Neuroendocrine (carcinoid) tumors, gastrointestinal stromal tumors, lymphomas, and sarcomas can also occur in the colon, but are rare.
Some facts about colorectal cancer-
1. Colorectal cancer is the third most common cancer worldwide.
2. It occurs in 1.8 million individuals each year globally.
3. It causes 862000 deaths per year globally.
4. The lifetime risk of developing colorectal cancer is one in 20.
Causes and risk factors for colorectal cancer-
Sometimes the DNA of a healthy cell changes during cell division. This leads to uncontrolled growth in that cell and cancer is formed.
Anything that increases someone’s risk of getting cancer is called a risk factor. Risk factor does not cause the disease but it only increases the risk.
Risk factors for colorectal cancer are:
1. Old age.
2. Western diet (high-fat diet, high in red meat and processed meat; low-fiber diet).
3. History of colorectal polyps (adenomatous polyp, large polyps and multiple polyps).
4. Family history of colorectal cancer (one-third of colorectal cancer patients have family members with the disease).
5. Past history of colorectal cancer (if you have previously been treated for colorectal cancer).
6. Inflammatory bowel disease of the colon; Ulcerative colitis and Crohn’s disease (risk of cancer increases with duration and severity).
9. Physical inactivity.
10. Smoking and consumption of alcohol.
11. Genetic risk factors (hereditary syndrome) –
A small percentage (about 5%) of patients with colorectal cancer have a gene change that is hereditary and increases the risk.
12. The common hereditary colon cancer syndromes are:
Hereditary nonpolyposis colorectal cancer (HNPCC) – HNPCC, also known as Lynch syndrome, increases the risk of colon cancer and some other cancers. People with HNPCC get colorectal cancer before the age of 50.
Familial Adenomatous Polyposis (FAP) – FAP is a rare disease that causes thousands of polyps to form in the large intestine. People with FAP have an increased risk of developing colorectal cancer before the age of 40.
13. Other rare hereditary syndromes: Peutz-Jeghers syndrome and MYH-associated polyposis
Symptoms of colorectal cancer-
Like other colon cancers, colorectal cancer usually has no symptoms in its early stages.
Symptoms of colorectal cancer include:
1. Change in bowel habits; persistent diarrhea, constipation, or the feeling that the stomach is not emptying completely.
2. Persistent feeling weak or tired and loss of appetite.
3. Weight loss.
4. Decrease in hemoglobin (anemia).
Abdominal pain or discomfort.
6. Red or black colored blood stain in stool.
Note that many of these symptoms can occur in diseases other than colorectal cancer.
Colorectal Cancer Screening (Diagnosis)-
1. Health examination-
Understanding the symptoms and examining the signs by a doctor is essential to reach the disease.
2. Faecal Occult Blood Test (FOBT) –
There is slight bleeding from the tumor which is not visible to the eye. It is detected by these tests.
These tests are of two types:
1 .Guaiac FOBT
2. Fecal Immunochemical Test (FIT) – This is a new and improved test.
Colonoscopy confirms the diagnosis of colorectal cancer.
A colonoscope is a flexible thin tube with a camera in it. This transmits the image of the inside of your large intestine to a monitor. If an abnormality is found, a small sample is also taken from it, which is called a biopsy.
A special type of CT scan is done to examine the large intestine. It is also called colonography.
Biopsy means taking a small sample of a tumor and examining it under a microscope. This is done by a pathologist. Gene testing can also be done on biopsy samples, if necessary.
6. To determine the spread of cancer (Staging)-
Cancer cells emerge from the cancerous lump and spread in the body in three ways; (1) Through blood (2) Through lymphatic (3) Directly into surrounding tissues.
Staging is knowing the spread of the disease. After colon cancer is diagnosed, we do tests to find out how far the tumor has spread. For this we do some of the following tests.
7. Blood test-
Different types of elements are examined in the blood. Some patients have anemia (low hemoglobin). Apart from this, liver and kidney tests are also done.
8. Tumor marker-
Most colorectal cancers produce a substance called CEA (carcinoembryonic antigen). A blood test checks its level in the blood. This is a useful test for monitoring cancer after treatment.
9. Computed Tomography (CT) Scan-
In this test, the patient is placed in a CT scanner. The X-ray beams then take images of the internal organs from all sides. Computers develop these images to give us accurate information about the internal situation. By injecting contrast we get a better image.
10. Magnetic Resonance Imaging (MRI) –
This test uses radio waves, and powerful magnetic fields, instead of X-rays. It is widely used in the staging of rectal cancer.
11. Positron Emission Tomography (PET) Scan –
Cancer cells take up a lot of glucose. In this test, radioactive glucose (18F-fluorodeoxy; FDG) is injected. This radioactive glucose goes into the tumor which we can see with the scanner.
These tests help us to stage the cancer. Broadly we classify cancer into three categories:
1. Localized – The cancer is confined to the organ in which it started.
2. Local spread – The cancer has spread to nearby lymph nodes or has come outside the wall of the organ in which it started.
3. Distant spread – Cancer has spread to distant organs, away from the organ of origin of the tumor. This is called metastasis.
TNM (tumour, node and metastasis) classification-
This classification has been developed by the American Joint Committee on Cancer (AJCC). It is used for precise classification of cancer stage. It is based on the following three key elements and ranges from Stage I to IV.
1. Tumor size (T) – how far into the layers of the colon has the cancer grown? Has the cancer spread to nearby structures or organs?
2. Spread to nearby lymph nodes (N) – Has the cancer spread to nearby lymph nodes? And in how many lymph nodes?
3. Spread to distant organs (metastasis) (M) – Has the cancer spread to distant lymph nodes or to distant organs such as the liver or lungs?
T, N and M are followed by numbers and letters that give further details. The higher the number, the more advanced the cancer. By combining the information from T, N and M, we assign a stage to the cancer. Colorectal cancer ranges from stage I to IV.
Stages I to III are localized disease and stage IV is spread cancer (metastatic disease).
The chances of recovering from cancer depend on the stage of cancer at the time of treatment. The fewer steps the better the chances.
Treatment of localized (limited) disease – surgery
The treatment of colon cancer depends on the stage and location of the tumour.
Surgery is the primary treatment for early-stage colorectal cancer.
In this, the cancerous part of the large intestine is removed along with the surrounding lymph nodes. The continuity of the intestine is then re-established by joining the cut sections of the intestine together (anastomosis).
Sometimes, when the tissues are not healthy, the anastomosis is not likely to connect. In such cases, the intestine is made through an opening in the abdomen called an ostomy (ileostomy or colostomy). It is temporary and is discontinued after improvement in the patient’s condition and chemotherapy (if required).
Surgery for colon cancer – COLECTOMY
Broadly speaking, the operation of colon cancer is called partial colectomy. This surgical procedure has different names depending on the part of the colon that is removed; Right hemicolectomy, left hemicolectomy, sigmoidectomy, transverse colectomy, right or left extended hemicolectomy and anterior resection.
Treatment of rectal cancer-
Chemotherapy, radiotherapy and surgery are combined to achieve the best results in advanced rectal tumours, which is called multimodal treatment. Currently, rectal cancer is treated with chemotherapy or chemoradiotherapy, which is called neoadjuvant treatment, followed by surgery.
In rectal cancer surgery, the cancerous part of the rectum is surgically removed along with the surrounding lymph nodes up to the healthy tissue. The surgical procedure is recognized with different names depending on the part of the rectum that is removed; Anterior resection, low anterior resection, ultra-low anterior resection or abdominoperineal resection.
Continuity of the intestine is restored by either joining the severed parts of the intestine together (anastomosis) or by opening an opening above the abdomen called a colostomy.
One important information needed before surgery is how close the tumor is to the anus. The decision whether or not to have a colostomy depends on the distance of the anus from the tumor and the extent of the intrusion.
Sometimes, the entire colon is removed. It is performed in patients whose remaining part of the colon is also affected by polyps, inflammatory bowel disease or intestinal obstruction.
There are two ways of operating for colorectal cancer;
1. In open surgery, a long incision is made in the abdomen.
2.Laparoscopic surgery is a special technique of performing an operation, which is also known as key-hole surgery, minimally invasive surgery or minimal access surgery. In this, instead of a large incision, the operation is performed by inserting special instruments and a camera through small holes in your abdomen. These instruments are made thin and long with special texture. The camera projects high-resolution images of the inside of your abdomen onto a large screen, which surgeons can see when they operate inside your abdomen. This technique is one of the most important inventions in the surgical field in the last few decades which has revolutionized the field of abdominal surgery. This surgical technique is now available and valid for most abdominal operations. The use of this technique is also beneficial in the operation of stomach cancer.
Benefits of laparoscopic surgery-
Open abdominal surgery requires a larger incision and can result in longer recovery times and longer hospital stays. Minimally invasive surgery means “less pain”, “minimum scarring” and “faster recovery”. Shorter stay in ICU and hospital. Due to the large view inside the abdomen on the large monitor, there is less blood loss during surgery. You can quickly start walking and eating by mouth. The risk of infection and hernia is also less as compared to open surgery.
Cancer will sometimes block the colon. In such cases, a stent may be placed to clear the blockage, improve the patient’s condition, and then surgery can be performed. If a stent cannot be placed or is not available, then direct surgery is performed. In such cases, usually, the ends of the intestine are not reattached, but are brought out as an ostomy. When the patient’s health improves, the ends of the intestine are later reattached in a second operation.
Treatment of advanced cancer-
1. Surgery –
Some stage IV cancers are confined to a few spots in the lungs, liver, and peritoneum. If the colon and all of these spots of cancer can be safely removed surgically, an attempt can be made to treat the cancer surgically.
- Liver resection
- This is a surgical procedure to remove the cancerous part of the liver, which is also called hepatectomy or metastasectomy.
- Lung resection
- Lung resection is a surgical procedure to remove the part of the lung that contains cancer.
- Cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (HIPEC)
Cytoreductive surgery with hyperthermic intraperitoneal chemotherapy (HIPEC) treats colorectal cancer that is confined to the abdominal peritoneum. During cytoreductive surgery, all visible tumor is surgically removed, and only microscopic cancer cells are left. The aim of HIPEC is to destroy the remaining microscopic cancer cells. In HIPEC, a concentrated and heated chemotherapy solution is given directly into the abdomen which kills those cells.
This approach helps patients survive longer and offers them a chance to remain cancer-free for a longer period of time. We give chemotherapy, radiotherapy or both before surgery in these patients.
2. Liver Directed Therapy-
Cancer that has spread to a few places in the liver is treated with embolization or ablation.
Embolization means cutting off the blood supply to the tumor. Blocking it with small particles and other agents by inserting a thin catheter into the vein that supplies blood to the tumor. Chemotherapeutic agents and radioactive beads can also be delivered directly to the tumor during this process, which is called chemoembolization or radioembolization.
Ablation uses extreme heat, cold, or chemicals to kill tumor cells. It is good for small tumors that are smaller than 2 cm. Radiofrequency ablation (RFA) uses high-frequency radio waves to generate heat and kill tumors. A needle is inserted into the tumor to be seen on an ultrasound or CT scan. Microwave ablation uses microwaves to generate heat and kill the tumor. Cryoablation, or cryotherapy, is the insertion of a metal needle into the tumor to freeze it and kill it. Tumor cells can also be killed by percutaneous ethanol injection (PEI).
5.Surgery – Palliative-
An ostomy (ileostomy or colostomy) is an operation to create an opening in the intestine and bring it out through a hole in the abdominal wall. A bag is properly placed over it in which the excreta is excreted. Ostomy is done when the tumor is large enough to block the intestines, the patient is unfit to undergo major surgery to remove the tumor, or the cancer has spread to other parts of the body.
Chemotherapy uses drugs to destroy cancer cells. Several medicines are given together for better results. These are given in a specific order on specific days in the form of a cycle.
1.Adjuvant chemo – In patients with localized colon cancer, chemotherapy is usually given after surgery. It destroys those cells which remain in the body even after the operation. The decision to give chemotherapy depends on the surgical stage. It is usually given if the cancer has spread to the lymph nodes or has moved into the outer layers of the intestine. In this way, chemotherapy helps reduce the risk of cancer recurrence and death from cancer.
2.Neoadjuvant chemo – If the tumor has grown excessively, chemotherapy is given before surgery. This will make the cancer smaller and give a better result from the operation later.
3. Palliative chemo – Chemotherapy in metastatic (spread) cancer prolongs life and improves its quality.
7. Targeted therapy-
Substances that identify and target cancer cells without harming normal cells.
They are made of the same type of immune cells.
Vascular Endothelial Growth Factor (VEGF) Inhibitors – VEGF causes tumors to grow and new blood vessels to form. VEGF inhibitors block this pathway.
Epidermal growth factor receptor (EGFR) inhibitors – EGFRs are proteins on the surface of cancer cells that help them grow. EGFR inhibitors block these proteins and stop cancer cells from growing.
Kinase inhibitors: Human cells contain many different kinases, and they help regulate important functions. Kinase inhibitors block these enzymes and stop cancer cells from growing.
It uses the patient’s immune system to fight the cancer. Immune checkpoint inhibitor therapy is a type of immunotherapy.
9. RADIATION THERAPY
Radiation therapy uses high energy X-rays to destroy cancer cells.
Diagnosis of disease-
1. Survival Rates-
The chances of survival after cancer treatment are measured in 5-year survival rates. It refers to the chance of getting rid of cancer and survival after treatment. Survival rate depends on the type and stage of cancer. After treatment for stage 1 colorectal cancer, 5-year survival is a little over 90%. For stage 2 it is around 60-90%. The 5-year survival for stage III colorectal cancer is 45 to 90% and for stage 4, the 5-year survival is about 15%.
Screening for colon cancer-
If we can detect diseases in time, we can treat them better.
Screening can detect diseases in people who are outwardly healthy and have no symptoms of disease.
It takes 10-15 years for an abnormal cell to develop into colorectal cancer. We can even remove them at the stage of a polyp and prevent them from becoming cancerous. Even if they do turn into cancer, we can detect them at an early stage, and a better cure is possible.
But, not everyone needs screening. Screening is done in people who have a higher than normal risk of developing colorectal cancer.
Screening tests for colorectal cancer include colonoscopy, CT colonography, sigmoidoscopy, and stool tests.
Who should be screened for colorectal cancer?
- If you are over 45
- If you have a family history of colorectal cancer or polyps
- If you have had colorectal cancer or polyps before
- If you have inflammatory bowel disease (ulcerative colitis or Crohn’s disease)
- If you have an inherited colorectal cancer syndrome such as familial adenomatous polyposis (FAP) or Lynch syndrome (HNPCC) in your family
- if you have a history of radiotherapy to the tummy (abdomen) or pelvic area to treat cancer
How to reduce the risk of getting colorectal cancer?
We can classify the risk factors of colorectal cancer into modifiable and non-modifiable. Age and genetic factors are non-modifiable and we cannot do anything about it.
- But we can reduce the risk by avoiding risk factors that we can control.
- We can reduce our risk by taking the following steps:
- Keep your weight under control
- Get regular physical activity and exercise
- Eat a healthy diet that is especially rich in fibrous fruits, vegetables and whole grains, while avoiding processed food
- Avoid smoking and tobacco
- Don’t drink alcohol
Disclaimer- After reading this article, you must have understood what is the cause, symptoms and treatment of colorectal cancer? But this article has been written for educational purposes, for more information consult a qualified doctor.
Stay alert! stay healthy! Thank you.
- Ovarian Cancer- Type, Symptoms, Causes, and Treatment
- Stomach Cancer- Causes, Symptoms and Treatment
- Bladder Cancer- Causes, Symptoms and Treatment
- Lung Cancer- Causes, Symptoms and Treatment
- Bone Cancer- Causes, Symptoms, Stages and Treatment
- Cervical Cancer- Causes, Symptoms and Treatment
- Oral Cancer – Causes, Symptoms and Treatment