WHY IS COLORECTAL CANCER A COMMON CANCER DIAGNOSIS?

Colorectal cancer was the fourth most commonly diagnosed cancer in Canada in 2024 (excluding non-melanoma skin cancers), according to the Canadian Cancer Society. In 2024, it was the second leading cause of death from cancer in men and the third in women.

While colorectal cancer accounted for 10% of all new cancer diagnoses in 2024, the good news is there has been a decline in cancer rates since the mid-80s in adults aged 50 and over. At the same time cancer rates for adults under 50 have been increasing since the mid-90s, although the death rate has not risen.

Part of the large intestine, the colon absorbs water and nutrients and passes waste to the rectum. Cancers of these organs are grouped together because there isn’t a clear border between them and they are made up of the same type of tissue.

When cells in the colon or rectum change and no longer grow or behave normally, this can lead to benign tumours or precancerous conditions – cells that are not yet cancer but have a higher chance of becoming cancer. The most frequent type of colorectal cancer begins in the gland cells that line the wall of the colon or rectum and help move stool through the colon and rectum.

WHAT ARE RISK FACTORS FOR COLORECTAL CANCER?

Despite a declining incidence rate in people over the age of 50, the risk of colorectal cancer increases with age. Men are also more likely than women to develop it.

Other genetic risk factors for colorectal cancer include a family history of colon cancer, especially if more than one relative has had the disease, and two genetic syndromes: familial adenomatous polyposis and Lynch syndrome.

In terms of lifestyle, obesity and high-fat, low-fibre diets that are heavy in red and processed meat, are known risk factors for colorectal cancer and may account for its prevalence, especially in North America, northwestern Europe, and Australia where the number of cases is the highest. Other lifestyle risk factors include:

• Not being physically active.
• Heavy alcohol use.
• Long history of smoking.

Please note, that a risk factor is something that increases the risk of developing cancer, but most cancers are the result of many risk factors. Cancer can also develop in people without risk factors.

WHAT ARE THE SYMPTOMS OF COLORECTAL CANCER?

The challenge with many cancers, including colorectal cancer, is that there may not be signs or symptoms in the early stages when the cancer is very small. Once a tumour grows larger, symptoms may appear, but other health conditions can cause symptoms similar to colorectal cancer. For a list of symptoms that may indicate colorectal cancer and should be investigated by your health care practitioner, please visit the Canadian Cancer Society website.

HOW DO YOU SCREEN FOR COLORECTAL CANCER?

According to the Canadian Cancer Society, there is strong evidence that colorectal cancer screening is effective in detecting cancers earlier and decreasing mortality. The majority of colorectal cancers begin as benign growths, called adenomatous polyps, which over time can grow in size and number thereby increasing the risk that they become cancerous. Identification and removal of polyps can help prevent the development of colorectal cancer.

In Alberta, colorectal cancer screening guidelines recommend the following types of screening:

• Fecal Immunochemical Test (FIT): This stool-based test is recommended every one to two years for people aged 50 to 74 years of age who have average risk of colorectal cancer – no signs or symptoms and the absence of family or personal history, or other high risk conditions.
• Flexible Sigmoidoscopy: Used to evaluate the lower part of the large intestinge, it involves a thin, flexible tube inserted into the rectum. A tiny video camera at the tip of the tube allows the doctor to view the inside of the rectum and most of the sigmoid colon. It’s recommended every five years.
• Colonoscopy: This procedure looks at the lining of the entire rectum and colon using an endoscope with a camera on the end; the colon is inflated with air to stretch out the lining so the doctor can inspect the entire surface. Recommended every 10 years.
• CT Virtual Colonscopy: This exam is a minimally invasive computed tomography (CT) scan that uses low-dose X-rays to produce two- and three-dimensional images of the large intestine (colon), rectum, and small intestine. If differs from a colonoscopy in that an endoscope is not used and your rectum is inflated with CO2, which is more comfortable and more readily absorbed by the body than room air. It’s recommended every five years.

HOW DO I GET COLORECTAL SCREENING?

To determine what type, or if, screening is appropriate for you, you will need to discuss with your doctor your medical and family history, risk factors, and if there are symptoms, how long symptoms have been present and how they affect daily activities. Your doctor would then provide you with a requisition for a specific procedure, if recommended.

Mayfair Diagnostics offers community-based private CT services as a complement to the public health care system, but whether public or private these exams must be requested by a health care practitioner. If a private CT virtual colonoscopy is indicated as a best next course of action, a requisition will be provided and the appointment can be booked.

Mayfair Diagnostics is owned and operated by over 50 radiologists who are sub-specialty trained, which guarantees an expert opinion of your imaging. Mayfair Diagnostics offers CT imaging at our Mayfair Place location. For more information, please visit our services page.

REFERENCES

The American Society of Colon and Rectal Surgeons (2020) “The Colon: What it is, What it Does and Why it is Important.” www.fascrs.org. Accessed March 4, 2022.

Canadian Cancer Society (2025) “Colorectal cancer statistics.” www.cancer.ca. Accessed February 4, 2025.

Canadian Cancer Society (2025) “Risk factors for colorectal cancer.” www.cancer.ca. Accessed February 4, 2025.

Colorectal Cancer Association of Canada (2021) “What is Colorectal Cancer?” www.colorectalcancercanada.com. Accessed March 4, 2022.

Toward Optimized Practice Working Group for Colorectal Cancer Screening. (2013) “Colorectal cancer screening: clinical practice guideline.” www.topalbertadoctors.org. Accessed March 4, 2022.