What is colorectal cancer?
The colon and rectum make up the large intestine, which is part of the digestive system. Most of the large intestine is made up of the colon; the different parts of the colon are described below:
- The first section, known as the ascending colon, extends upward on the right side of the abdomen.
- The second section, known as the transverse colon, goes across the body from the right to the left side.
- The third section, known as the descending colon, descends (travels down) on the left side.-
- The fourth section, known as the sigmoid colon, joins the rectum, which connects to the anus.
The ascending and transverse sections of the colon together, are called the proximal colon. The descending and sigmoid colon are called the distal colon.
The colon is where the body extracts water and salt from the remaining food or waste matter. The waste then moves through the rectum and exits the body through the anus.
Most colorectal cancers start as a growth, called a polyp, on the inner lining of the colon or rectum. Some types of polyps can change into cancer over time, usually after many years. The different types of polyps are:
- Adenomatous polyps (adenomas): These polyps sometimes change into cancer and are therefore refer red to as pre-cancerous polyps.
- Hyperplastic polyps and inflammatory polyps: These polyps are more common and generally do not develop into cancer.
- Sessile serrated polyps and traditional serrated adenomas: These polyps have a high risk of developing into colorectal cancer.
Screening helps to detect cancer in people who have no symptoms of the disease. Regular colorectal cancer screening is one of the most powerful weapons against colorectal cancer .
Screening can often find colorectal cancer early, when it’s small, hasn’t spread, and might be easier to treat. Regular screening can even prevent colorectal cancer. A polyp can take as many as 10 to 15 years to develop into cancer. During the screening procedure, doctors can detect and remove polyps before they become cancerous.
Metastatic colorectal cancer
Metastatic colorectal cancer occurs when the cancer cells within the tumour have spread from its original location to other parts of the body.
The wall of the colon and rectum is made up of many layers. Colorectal cancer starts in the innermost layer (the mucosa) and can grow outward through some or all the other layers. When cancer cells are in the wall, they can grow into blood vessels or lymph vessels and travel to nearby lymph nodes or to other parts of the body.
Regardless of where a cancer may spread, it’s always named for the place where it started. For example, colorectal cancer that has spread to the liver is called metastatic colorectal cancer, not liver cancer.
Symptoms of colorectal cancer
In its early stages, colorectal cancer may have no symptoms.When symptoms appear, they usually vary, depending on the cancer’s size and location in the large intestine. Some of the symptoms that may be experienced include:
- a change in bowel habit, such as diarrhoea, constipation or smaller, more frequent bowel movements
- a change in appearance of bowel movements (e.g. narrower stools or mucus in stools)
- a feeling of fullness or bloating in the abdomen or a strange sensation in the rectum, often during bowel movement
- a feeling that the bowel hasn’t emptied completely
- blood in the stools or on the toilet paper
- unexplained weight loss
- weakness or fatigue
- rectal or anal pain
- a lump in the rectum or anus
- abdominal pain or swelling
- a low red blood cell count (anaemia), which can cause tiredness and weakness
If any of these symptoms are observed, please consult a doctor, to ensure that the cause can be diagnosed and treated, if necessary.
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Risk factors for colorectal cancer
Some of the factors that may increase the risk of colon cancer include:
- Age: Most people with colorectal cancer are over 50, and the risk of having the disease increases with age.
- A personal history of colorectal cancer: Individuals who have previously been diagnosed with colorectal cancer have a greater risk of having the disease in the future.
- Bowel diseases: Individuals who have an inflammatory bowel disease, such as Crohn’s disease or ulcerative colitis,
are at a high risk of having colorectal cancer, particularly if they have had the inflammatory bowel disease for more than eight years.
- Lifestyle factors: Lifestyle factors which may increase the risk of colorectal cancer include being overweight, consumption of a diet high in red meat and processed meat, heavy alcohol consumption and smoking.
- Other diseases: Individuals who have had ovarian or endometrial cancer may have an increased risk of colorectal cancer.
- Family history of colorectal cancer: There is a high risk of developing colorectal cancer if there is a blood relative who has had the disease. The risk is greater if more than one family member has had the disease.
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Diagnosis of colorectal cancer
Diagnostic tests are usually conducted to diagnose colorectal cancer because of symptoms experienced, strong family history of colorectal cancer, or a positive result from another screening test.
Some general tests that may be carried out to diagnose colorectal cancer include physical examination of the rectum, anus, blood tests and an immunochemical faecal occult blood test (iFOBT). More specific tests used to diagnose colorectal cancer include colonoscopy, CT colonography and flexible sigmoidoscopy.
Physical examination: This involves examination of a patient’s body and abdomen by a doctor, for any swelling. The doctor may also perform a digital rectal examination (DRE). The doctor carries out this procedure by inserting a gloved, lubricated finger into a patient’s anus, to establish if there are any lumps or swelling.
Blood tests: These may be done to assess a patient’s general health and to establish if blood is lost in the stool. Tests may also be carried out to determine if the liver is functioning properly and to check that the number of red blood cells are within the normal range.
Immunochemical faecal occult blood test (iFOBT): An iFOBT may be recommended by a doctor for patients with low red blood cell count, unexplained weight loss, abdominal pain, or patients with changes to their bowel habits. An iFOBT involves examination of a patient’s stool sample for microscopic traces of blood, which may be an indication of the presence of polyps, cancer or another condition of the colon or rectum. In instances where an iFOBT confirms presence of blood in the stool sample, the doctor may recommend a colonoscopy within 4 months of receiving the iFOBT result.
Colonoscopy: During colonoscopy, a doctor examines the colon and rectum with a colonoscope (a flexible tube about the width of a finger, with a light and small video camera on one end). The doctor would usually recommend a bowel preparation*, to clean the bowel before a colonoscopy.
The colonoscope is inserted by the doctor through the anus into the rectum and colon. During the procedure, if the doctor sees any suspicious-looking areas like polyps, these will be removed for further examination by a pathologist, for signs of disease.
A doctor with a colonoscope
Flexible sigmoidoscopy: A flexible sigmoidoscopy is similar to a colonoscopy, except that it doesn’t examine the entire colon. This procedure makes use of a sigmoidoscope (a flexible, lighted tube about the thickness of a finger with a small video camera at the end) to examine the rectum and lower part of the colon. A light bowel clean-out*, usually with an enema is required before a flexible sigmoidoscopy.
The sigmoidoscope is inserted through the anus, into the rectum and then moved into the lower part of the colon. Images from the sigmoidoscope are seen on a video screen; the doctor observes these to find and remove any abnormal areas.
This test may not be commonly used as a diagnostic test for colorectal cancer as it examines only a third of the colon and can’t remove all polyps.
CT colonography: This procedure, also called virtual colonoscopy, is an advanced type of computed tomography (CT) scan of the colon and rectum, which can create 3-dimensional pictures of the inner parts of the colon and rectum, and show abnormal or suspicious-looking areas like polyps. This procedure may be recommended if the colonoscopy was unable to show all the colon or if a colonoscopy is considered unsafe. During the procedure, if the doctor observes polyps or other suspicious-looking areas, a coloscopy may still be required to remove them or to properly explore the area.
This test may not be commonly used as a diagnostic test for colorectal cancer as it can produce false-positive results, exposes the patient to radiation, and can’t be used to remove any polyps discovered during the test.
* details of the bowel preparation or light bowel clean-out will be explained to the patient by the doctor or other Healthcare Professionals on the patient’s healthcare team.
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Treatment options for colorectal cancer
The medical team will recommend treatment based on:
- what will lead to the best outcome
- the location of the cancer in the colon or rectum
- whether and how the cancer has spread
- the patient’s general health
- the patient’s preferences
Treatment options include surgery, chemotherapy, radiation therapy and targeted therapy.
Surgery to remove the colon or part of it is called a colectomy. During this procedure, a surgeon will remove the part of the colon that contains the cancer, as well as some of the surrounding area, like nearby lymph nodes to reduce or prevent the spread of the cancer.
The surgeon will then either reattach the healthy portion of the colon or create a stoma, depending on the extent of the colectomy.
A stoma is a surgical opening in the wall of the abdomen through which waste passes into a bag. This eliminates the need for the lower part of the colon. This is called a colostomy.
Other types of surgery include:
Endoscopy: A surgeon may be able to remove some small, localized cancers using this procedure. They will insert a thin, flexible tube attached to a light and camera. The tube also has a channel, through which attachments may be used to collect cancerous tissue.
Laparoscopic surgery: A surgeon will make several small incisions in the abdomen. This may be an option to remove larger polyps.
Palliative surgery: The aim of this type of surgery is to relieve symptoms in cases of untreatable or advanced cancers. A surgeon will attempt to relieve any blockage of the colon and manage pain, bleeding, and other symptoms.
Chemotherapy uses medicines to kill or slow the growth of cancer cells while doing the least possible damage to healthy cells. If the cancer has spread outside the bowel to lymph nodes or to other organs, chemotherapy may be recommended:
Before surgery (neoadjuvant chemotherapy) – Some individuals with rectal cancer, may have chemotherapy before surgery to shrink the tumour and make it easier to remove. In this instance, chemotherapy may be administered together with radiation therapy (chemoradiation).
After surgery (adjuvant chemotherapy) – Chemotherapy may be administered after surgery for either colon or rectal cancer to get rid of any remaining cancer cells and reduce the chance of the cancer coming back.
On its own – If the cancer has spread to other organs, such as the liver or lungs, chemotherapy may be used either to shrink the tumours or to reduce symptoms of the disease.
Common side effects of chemotherapy include:
- hair loss or thinning
- mouth sores and ulcers
- changes in appetite, taste or smell
- sore hands and feet
The side effects experienced depend on the type of medicine administered and the dose. The medical oncologist or nurse will discuss the likely side effects, including how they can be prevented or controlled with medicine.
It is important to keep a record of the names of the chemotherapy medicines and doses administered. This will be very helpful if there is need to be taken to the emergency department.
Targeted therapies are used to treat colorectal cancer when the disease is advanced (metastatic).
Targeted therapy medicines work differently from chemotherapy medicines. While chemotherapy medicines affect all rapidly dividing cells and kill cancerous cells, targeted therapy medicines affect specific molecules within cells to block cell growth.
Examples of targeted therapies are medicines which target specific features of cancer cells, known as the epidermal growth factor receptor (EGFR). These medicines are only effective in colorectal cancer patients, who have a normal RAS gene, known as the RAS wild-type gene. The tumour will be tested for changes in the RAS gene, to ensure the patient has the RAS wild-type gene, before treatment with any of these medicines can be initiated.
The side effects of targeted therapies depend on the type of medicine used. Common side effects of some targeted therapies may include:
- high blood pressure
- redness, swelling, acne-like rash, dry skin
Radiotherapy involves the use of a controlled dose of radiation, such as focused x-ray beams, to kill or damage cancer cells. The radiation is targeted to the specific area of the cancer, and treatment is carefully planned to do as little harm as possible to the normal body tissues near the cancer. Radiation therapy is often combined with chemotherapy (chemoradiation). This is because chemotherapy makes cancer cells more sensitive to radiation.
Radiation therapy is not generally used to treat locally advanced colon cancer. However, for locally advanced rectal cancer, a short course of radiation therapy or a longer course of chemoradiation is used to shrink the tumour before surgery. This ensures that the cancer is as small as possible before it is removed, making it easier for the surgeon to completely remove the tumour. This also reduces the risk of the cancer coming back. Occasionally, if the rectal cancer is found to be more advanced than originally thought, radiation therapy may be used after surgery to destroy any remaining cancer cells.
Side effects of radiation treatment may include:
- mild skin changes that resemble sunburn or suntan
- appetite loss
- weight loss
Most side effects will resolve or subside a few weeks after completing treatment.
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Questions to ask your doctor about colorectal cancer
It’s important to have honest, open discussions with your cancer care team. They want to answer all your questions, to enable you make informed treatment and life decisions. Some of the questions that may be included in a question checklist are listed below.
When informed of a colorectal cancer diagnosis:
- Where is the cancer located?
- Has the cancer spread? If so, where has it spread? How fast is it growing?
- Will I need other tests before a decision is made on treatment?
- Do I need to consult other doctors or health professionals?
When deciding on a treatment plan
- What are my treatment options?
- What do you recommend and why?
- If surgery is part of my treatment, will I need a stoma? If so, will it be temporary or permanent? Who will teach me how to care for it?
- Should I get a second opinion? How do I do that? Can you recommend someone?
- How long will treatment last? Will I have to stay in hospital?
- How might treatment affect my daily activities? Can I still work full time?
- What are the chances that I can be cured of this cancer with these treatment options?
- What would my options be if the treatment doesn’t work or if the cancer comes back after treatment?
- How will I know if the treatment is working?
- What are the risks and side effects of each treatment?
- What symptoms or side effects should I immediately inform you of?
- Can I work, drive and carry on with my normal activities while having treatment?
- How can I contact you on nights, holidays, or weekends if there is a need to?
- Can you suggest a mental health professional I can see if I start to feel overwhelmed, depressed, or distressed?
- How often will I need check-ups after treatment?
- If the cancer returns, how will I know? What treatments could I have?
- What symptoms should I watch for?
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