Colorectal Cancer
Colorectal cancer is the third most common cancer in Canada1 and most cases occur among adults 50 years of age and older. We also refer to colorectal cancer (CRC) as bowel cancer, colon cancer, and rectal cancer. It affects both men and women; 1 in 14 men will receive a diagnosis in their lifetime and 1 in 18 women.1 This cancer usually develops from benign polyps called adenomas. Not all polyps develop into cancer, and in those that do, it typically takes 10 to 15 years. This means that physicians typically remove any visible polyps during a colonoscopy to prevent them from becoming cancerous. With screening and early detection, colorectal cancer can be curable and easy to treat.
Risk Factors
These factors can increase your risk for colorectal cancer:
- increasing age, beginning at about 50 years of age
- smoking tobacco
- drinking alcohol
- family history of colorectal cancer or polyps, uterine cancer, or ovarian cancer
- extensive inflammatory bowel disease involving the colon
- overweight or obesity
- consuming a diet high in processed and red meats
- physical inactivity
Hereditary conditions that develop from genetic changes, such as familial adenomatous polyposis and hereditary nonpolyposis colorectal cancer (Lynch syndrome), can increase your risk. Close to 5% of all colorectal cancer diagnoses develop from these.2 Your doctor will determine if you have familial adenomatous polyposis during a colonoscopy and an evaluation of your family history. You may have Lynch syndrome if you have relatives with this condition, but you can also detect it by way of genetic testing with the help of your treating physician.
Early Warning Signs
These symptoms might be signs of colorectal cancer:
- blood on or in your stool, either bright red or very dark in colour; if you observe this, contact your doctor immediately
- unexpected changes in normal bowel habits, such as diarrhea and/or constipation
- constant abdominal pain
- feeling that the bowel does not completely empty
- unplanned weight loss
- constant fatigue
Prevention
Limit smoking tobacco and drinking alcohol since these may increase your risk. For instance, drinking 25 g of alcohol (a standard drink contains 14 g) each day can increase your risk by 20%. Smoking also makes it more difficult for cancer treatments to work effectively.3 However, exercising regularly, getting enough vitamin D, and consuming a diet that is rich in fruits, vegetables, fibre, and calcium, can lower your risk.4
Screening
Colonic polyps are common among all adults. If you are between 50 and 74 years of age, you are at an average risk for colorectal cancer even if you have no symptoms. If you are 75 years of age or older, you should discuss with your physician if, and how often, you should go for screening.
The goal of screening is early detection and the removal of polyps, without which cancers do not form, or early detection of cancer in a more successfully treatable form.
Those who are at an average risk will typically receive screening recommendations for a fecal immunochemical test (FIT) or, in certain regions in Canada, a fecal occult blood test (FOBT), every one to two years.5 Physicians might also recommend a sigmoidoscopy or colonoscopy every 10 years.
If you have a family history of colorectal cancer, the screening recommendations are:
| Family History | Screening |
| • a first-degree relative (e.g., parent or sibling) that received a diagnosis of colorectal cancer before 60 years of age | • screen once every five years
• first screening should take place at 40 years of age, or 10 years before the relative’s age of diagnosis, whichever comes first |
| • three or more relatives have colorectal cancer, or a first-degree relative received a diagnosis before the age of 40 | • consider genetic testing and/or counselling for specific hereditary diseases and, depending on the results, your screening interval can be set |
Inflammatory Bowel Disease
If you have inflammatory bowel disease (primarily Crohn’s disease or ulcerative colitis) affecting your colon, you are at a slightly higher risk of developing colorectal cancer. Your doctor might recommend screening every one to two years after you have had disease in your colon for eight to ten years.
Screening Tests
Your healthcare provider will recommend a screening test based on your preferences, risk, medical history, and what is available in your region. The tests available are:
- fecal immunochemical test (FIT)
- fecal occult blood test (FOBT)
- flexible sigmoidoscopy
- colonoscopy
- virtual colonoscopy
Fecal Immunochemical Test
The fecal immunochemical test (FIT) focuses on detecting hidden (occult) blood in the lower gastrointestinal (GI) tract. Your physician will likely recommend this test since it is the preferred screening test in most provinces and territories.
Ask your healthcare provider if you are eligible for this test. The kit will give you instructions on how you can collect a sample of your stool to drop off at a lab for examination. If the laboratory finds blood, then your doctor will request further tests. They might also recommend doing this test every two years.
If you have a history of colorectal cancer, iron deficiency anemia, or inflammatory bowel disease, then you are not eligible for the FIT, as these conditions can affect your results. Contact your physician to learn more about the right screening method for you.
Fecal Occult Blood Test
The fecal occult blood test (FOBT) will require you to provide one or more stool samples over a few days, depending on the type of testing kit your doctor provides. There might be special instructions on the foods and medicine you can or cannot consume before you collect samples. A lab technician will then look for hidden blood in the stool, since it could be an indication of colon cancer. If they detect any, you will need additional tests. If they do not detect blood, then your doctor may recommend the FOBT every two years.
Use of FOBT is now less common in Canada in favour of FIT; however, Manitoba and Quebec primarily use this test instead of FIT.
Flexible Sigmoidoscopy
Your doctor will insert a flexible tube with a light and tiny camera (sigmoidoscope) into the lower portion of your colon, through the rectum. They may take a small amount of tissue (biopsy) from specific areas for examination in a laboratory. They can also remove entire polyps on the spot. This procedure typically lasts about 20 minutes and you do not need sedation. For the general population, a flexible sigmoidoscopy will only need to occur every ten years.
This test does not check all possible sites for abnormalities. Depending on your medical history, your doctor might also recommend having both FIT (or FOBT) and flexible sigmoidoscopy in combination every five years.
Colonoscopy
Your doctor will typically recommend a colonoscopy if your lab results indicate further testing or if you are at a higher risk. This procedure is more common than sigmoidoscopy in Canada.
A colonoscopy requires sedation, so make sure you have someone available to take you home afterward. Your healthcare team will administer a combination of two medications intravenously: a benzodiazepine to help you relax and an opioid to decrease pain. Once they take effect, your physician will insert a thin flexible tube with a tiny camera (colonoscope) into your rectum. This allows your physician to see the inside of your bowel and painlessly take a biopsy of specific areas, which a lab technician will examine later. Your doctor might also remove polyps during the procedure. A colonoscopy can last between 20 and 45 minutes, but you might need to be at the hospital for about two to three hours for preparations and monitoring. During the procedure your doctor will use air to expand the area for better visualization, so you might pass a fair bit of gas afterward. Also, the physician can use a part of the scope to suction out any extra fluid and debris, so don’t worry about this.
Colonoscopies are very safe, and most people report that the most unpleasant part of the procedure is the preparation. However, there is a minimal risk of slight tearing of the colon wall or bleeding, and sedation can have other risks. Speak to your physician about any concerns you might have.
Virtual Colonoscopy
Virtual colonoscopy, also known as computerized tomographic (CT) colonography, is a less invasive alternative to standard colonoscopy.6,7 It uses low dose radiation CT or magnetic resonance imaging (MRI) scans to create two-dimensional (2D) or three-dimensional (3D) images of the colon. You do not need to take sedatives and pain relievers. However, virtual colonoscopy is not as effective as conventional colonoscopy in finding smaller polyps. Also, it is only a diagnostic procedure that does not allow for the removal of polyps, which requires conventional colonoscopy.
You will need to lie down on your back on the CT examination table, or the technician might ask you to lie down on your side or your stomach, or raise your arms above your head, so they can obtain the best images. The technologist will insert a small, thin tube two inches into your rectum. They will then gently pump air into the colon to clear any folds or wrinkles that might hide polyps from view. You will need to hold your breath for about 15 seconds as the table moves through the scanner, but this procedure only takes about 15 minutes.
You will have to prepare your bowel for this screening method (see below).
If you are pregnant, have active IBD, diverticulitis, or have a history of bowel perforation, you might not be eligible for virtual colonoscopy.7
Research is underway on expanding physicians’ ability to view the colon by combining immersive virtual reality (VR) with virtual colonoscopy.6 This would allow doctors to have a 360° view, in 3D, of the colon in real-time and could lead to identifying more polyps.
Preparing for Scoping
The main goal in preparing for a sigmoidoscopy, colonoscopy, or virtual colonoscopy, is to have an empty colon to make it easier for your physician to examine this area.
To prepare the colon, you will need to take a purgative (a drug that causes evacuation of the bowels) or laxative one to two days before your procedure. A variety of purgatives are available over the counter in your local pharmacy and your gastroenterologist might have a preferred one for you to use. Your gastroenterologist might also advise you to modify the way you take some of your medications in the days leading up to the procedure.
During bowel preparation, drink plenty of clear liquids to avoid dehydration and to help completely empty out your colon. Avoid eating solid foods for at least 24 hours before the day of your scope and stop drinking clear liquids three hours before. Sometimes, doctors advise their patients to consume an electrolyte replacement drink (e.g., Gatorade®) to combat dehydration, electrolyte loss, and kidney impairment. Remember, stay within close access to a toilet, as you will experience frequent, watery bowel movements that come on suddenly.
After a scope, your healthcare provider might recommend that you follow a temporary diet to recover, which usually includes light meals and other foods that are easy to digest.
Purgatives and Laxatives
A commonly used purgative is polyethylene glycol (PEG). It comes in flavoured formulations to disguise its salty taste (Colyte® and PegLyte®). The main disadvantage is that you must drink 4 L of the solution during a short duration, which can be too much for some people to manage.
Another purgative is a combination of sodium picosulfate, magnesium oxide, and citric acid solution (Pico-Salax®). It is the only product that works as an osmotic and stimulant. All purgatives are osmotic agents, which pull water from the body into the bowel. The stimulant further helps the bowel eliminate fecal matter. Clinical studies show that patients tolerate Pico-Salax® better than other preparations, and experience fewer side effects. It is available in cranberry and orange flavours, has lactose-free options, and is a manageable volume to drink (one 5 oz glass, twice during the day). However, you need to drink at least four to six large glasses of water or clear liquid following each 5 oz glass dose. Pico-Salax® is also the only purgative that children who are one year of age and older can safely use.
MoviPrep® is a PEG-based laxative but you only need to drink 2 L of the preparation fluid, along with 1 L of any clear liquid (i.e., clear juice or broth). You can take MoviPrep® in two doses: one in the evening before the colonoscopy and one on the morning of the procedure. This product works very quickly, within an hour or so of taking it, so make sure you have access to a toilet. Unlike other PEG-based bowel preparations, MoviPrep® contains a form of vitamin C (ascorbic acid) and the product has a light citrus flavour similar to chewable vitamin C tablets. More PEG-based laxatives exist, such as Bi-PEGLYTE®, Clearlax®, and others.
People have different tolerances for purgatives and laxatives. Fortunately, there are a variety of products to choose from. Ask your doctor which product might be best for you.
Management
Medications and Surgery
There are effective therapies and medicines to treat colon cancer, such as surgery, chemotherapy, radiotherapy, targeted therapy, and immunotherapy. Surgical resection continues to be the only way to cure colon cancer in its early stages.4 If the cancer has advanced and spread to other parts of the body beyond its original tumour location (metastasized), your healthcare team will use several measures to control the disease, such as chemotherapy, biologics, and palliative surgery.
You might experience side effects from treatments and the cancer itself. Your healthcare team will discuss these with you and schedule follow-up appointments, as well as screening, to make sure that they have removed all of the cancer and/or to check for any signs of the disease recurring or progressing.
Biomarkers
In cancer research, biomarkers are biological markers that a tumour or an individual’s body creates, such as DNA, RNA, protein, or small molecules.8 Biomarkers can help determine recommendations tailored to our specific genes, lifestyle, and more. We now know that molecular mutations can occur throughout the development of colorectal cancer, and healthcare professionals already use validated biomarkers for diagnosis and treatment. Others are in development or undergoing testing in clinical trials.
For instance, studies have found that close to half of individuals with colon cancer carry the RAS gene, with 36% also carrying mutations for KRAS and 3% for NRAS. Both KRAS and NRAS can indicate whether a person may not respond to anti-EGFR therapy, such as cetuximab (Erbitux®) or panitumumab (Vectibix®).9 Meanwhile, research has shown that these therapies are beneficial for individuals with RAS wild-type tumours. Consult your treating physician for more information on testing for biomarkers.
Lifestyle and Dietary Modifications
Exercise and diet can play a significant role in improving your quality of life and survival after diagnosis. Engaging in regular exercise, such as at least 150 minutes per week of aerobic activity (e.g., brisk walking), 90 minutes per week of running, or muscle-strengthening exercises at least two days per week, can have beneficial effects on your health throughout your care.10 If this exercise regimen is not feasible for you, try to be as physically active as possible when you can. For example, if you spend most of your day sitting down, then take frequent breaks to stand up, stretch, and walk around.
Limit your intake of sugar-sweetened beverages, such as sodas, sports drinks, and fruit or vegetable juices with added sugar, since these are associated with colon cancer recurrence and mortality. Instead, try to eat five or more servings per day of vegetables and fruits. Restrict your consumption of red and processed meats, as well as foods high on the glycemic index and refined carbohydrates, such as bread, pasta, white rice, cakes, cookies, and other sweets and desserts. These dietary limitations may seem gloomy, but with the help of a registered dietitian, you can tailor your diet to your preferences, eat delicious meals, and still have a healthy lifestyle!
Outlook
Fortunately, there are screening programs and initiatives across Canada that promote the early detection of colorectal cancer. Combined with improvements in diagnosis and treatments, more and more individuals with colorectal cancer survive and continue to live a good quality of life.