Colorectal cancer is a cancer that starts in the colon or the rectum. Colon and rectal cancers arise from the same type of cell and have many similarities. It is for this reason they are often referred to collectively as “colorectal cancer”. The cells lining the colon or rectum can sometimes become abnormal and divide rapidly. These cells can form benign (non-cancerous) tumours or growths called polyps. Although not all polyps will develop into colorectal cancer, colorectal cancer almost always develops from a polyp. Over a period of many years, a polyp’s cells may undergo a series of DNA changes that cause them to become malignant (cancerous). At first, these cancer cells are contained on the surface of a polyp, but can grow into the wall of the colon or rectum where they can gain access to blood and lymph vessels. Once this happens, the cancer can spread to lymph nodes and other organs, such as the liver or lungs—this process is called metastasis, and tumours found in distant organs are called metastases.
Polyps larger than one centimeter, with extensive villous patterns, have an increased risk of developing into cancer. The vast majority of colorectal cancers are adenocarcinomas, tumours that arise from the mucosa cells of the colon.
Did You Know…
- Symptoms of colorectal cancer can be mistaken for other ailments. Please click on the Section entitled “Symptoms” to learn how you can distinguish between colorectal cancer and other harmless conditions.
- Patients with Crohn’s Disease and Ulcerative Colitis have a higher risk of developing colorectal cancer. To learn more, visit our “Risk Factors” Section.
Experts are not completely sure why colorectal cancer develops in some people and not others. However, several risk factors have been identified over the years. Risk factors for colorectal cancer can be divided into two main groups: those that you cannot change and those that are lifestyle-related and, therefore, subject to change.
Risk Factors You Cannot Change:
- Age: The risk of developing colorectal cancer increases with age. The disease is more common in people over the age of 50, and the chance of developing colorectal cancer increases with each decade. However, colorectal cancer has also been known to develop in younger people as well. (Patel, 2009: Gairdiello, 2008)
- Type II Diabetes
- Personal History of Colorectal Polyps/Cancer
- Personal History of Inflammatory Bowel Disease (IBD)
- Family History of Colorectal Cancer or Adenomatous Polyps
- Inherited Syndromes: Genetic syndromes passed through generations of one’s family can increase one’s risk of developing colorectal cancer.
- Racial & Ethnic Background: African Americans and Jews of Eastern European descent (Ashkenazi Jews) are two groups most affected by colorectal cancer.
- Personal History of Other Cancers
Lifestyle-Related Risk Factors That Can Be Altered:
- Sedentary Lifestyle/Physical Inactivity
- Alcohol Consumption
Did You Know….
- Being physically inactive is a risk factor for colorectal cancer. A simple walk around the block can help boost your activity level.
- Colorectal Cancer Canada is part of a global effort, the Never Too Young Program, dedicated to the increasing number of patients under the age of 50 being diagnosed with colorectal cancer.
- Low intake of fruits, vegetables and fibre can increase your risk of developing colorectal cancer. Add colorful vegetables and fruits to your diet.
Many people with colorectal cancer experience no symptoms in the early stages of the disease. When symptoms appear they will likely vary depending on the cancer’s size and location in the large intestine, also known as the colorectum. Studies suggest that the average duration of symptoms (from onset to diagnosis) is 14 weeks. There is no association between overall duration of symptoms and the stage of the tumor. Therefore, it is best to get regular screenings rather than rely on colorectal cancer symptoms to alert one to the presence of a tumor. This is because colorectal cancer can grow for years before causing any symptoms. But, knowing what to look out for most certainly cannot hurt. Typical symptoms resulting from colorectal cancer are:
- Narrow Stools
- Abdominal Cramps
- Bloody Stools
- Unexplained Weight Loss/Loss of Appetite
- Sense of Fullness
- Nausea & Vomiting
- Gas & Bloating
Did You Know…
- Colon cancer can be present for several years before symptoms develop. Screening is critical.
- The left side of the colon is narrower than the right colon. Therefore, cancers of the left colon are more likely to cause partial or complete bowel obstruction. This can cause symptoms of constipation, narrowed stool, diarrhea, abdominal pains, cramps, and bloating.
Diagnosing colorectal cancer starts with a visit to your family doctor who will review your symptoms, conduct a physical exam and possibly order blood tests. If results suggest that colorectal cancer might be present, your doctor may recommend one or more additional tests for an official diagnosis. A Flexible Sigmoidoscopy or a Colonoscopy are common diagnostic tests that allow your doctor to remove tissue and perform a biopsy to confirm the presence of cancer. If colorectal cancer is detected, you may need further tests to find out the position and size of the cancer, as well as determine the extent of your cancer. These tests may include blood tests and image tests such as an Ultrasound or CT scan.
Staging of colorectal cancer refers to how far a cancer has spread on a scale from 0 to IV, with 0 meaning a cancer that has not begun to invade the colon wall and IV describing cancer that has spread beyond the original site to other parts of the body. Staging describes the extent of the cancer based on:
- how many layers of the bowel wall are affected,
- whether lymph nodes are involved, and
- if there it has spread to other organs.
For colorectal cancer, staging often can’t be completed until after surgery to remove the primary tumour along with surrounding tissue (containing lymph nodes), and possibly lesions found on other organs.
Below is generally how the cancer is referred to between doctor and patient:
- The cancer is confined to the innermost layer of the colon or rectum. It has not yet invaded the bowel wall. Is also referred to as high grade dysplasia
- The cancer has penetrated some or several layers of the colon or rectum wall.
- The cancer has penetrated the entire wall of the colon or rectum and may extend into nearby tissue(s).
- The cancer has spread to the lymph nodes.
- The cancer has spread to distant organs, usually the liver or lungs.