In the United States, cancer is second only to heart disease in terms of annual deaths. Almost 600,000 people die from some form of cancer every year, and colorectal cancer is the second leading cause of cancer death for both men and women. More than 140,000 new cases are diagnosed every year of this largely preventable disease. March is National Colorectal Cancer Awareness Month. The main goal of the campaign is to raise awareness of the disease, but also to encourage people to get early screening for colorectal cancer. While it can be a deadly disease, catching it early can make an enormous difference in terms of both life expectancy and quality of life.
What Role Does the Colon Play in Digestion?
Although frequently asymptomatic, colorectal cancer can be related to a variety of gastrointestinal symptoms. It’s helpful to understand how the colon fits into the digestive process. When food enters the mouth and is chewed into a pulp, that mass (called a food bolus) makes its way down the esophagus and into the stomach. Digestive juices and muscle contractions, called peristalsis, act on the food bolus to reduce it to a semi-liquid material called chyme. The chyme then enters the small intestine where additional enzyme-rich juices further break it down into components that can be absorbed into the bloodstream and carried around the body to be used by cells.
After the small intestine, the chyme (composed mostly of waste materials and bits of undigested food at this point) enters the large intestine via the ileocecal valve. The cecum is the first portion of the colon followed by the ascending colon, transverse colon, descending colon, sigmoid colon, rectum, and anal canal.
The small intestine is primarily responsible for true “digestion” in the sense of utilizing the nutrients in food, and it is the colon that processes the remaining waste products by absorbing water and salts and forming stool. Though the colon doesn’t produce digestive enzymes, the gut flora present there can use the waste products in the stool to synthesize valuable vitamins. By the time the stool reaches the sigmoid colon, it is mostly solid and can be expelled through the anal canal.
What is Colorectal Cancer?
Colorectal cancer is an abnormal growth of mutated cells that can develop in either the colon or the rectum. Though the terms colon cancer and rectal cancer are used to describe cancers in those specific areas, colorectal cancer is a commonly used term to group the two conditions together since they both share similar attributes. Like any type of cancer, the abnormal growth of cells starts small and localized but can spread to other parts of the body and lead to major problems for multiple body systems.
Colorectal cancer typically begins in the inner lining of the colon or rectum with small, fleshy growths called polyps. Though typically benign at first, polyps can become cancerous over time if they aren’t removed. Some polyps, such as inflammatory or hyperplastic polyps, are considered to have low malignancy potential and are therefore unlikely to lead to cancer. Adenomatous polyps, on the other hand, are considered precancerous and thus have a much higher likelihood of leading to cancer. Polyps can usually be detected and, more often than not, removed during a colonoscopy.
Symptoms of colon cancer, if present, can vary and can be very similar to other digestive diseases, such as inflammatory bowel disease, irritable bowel syndrome, or hemorrhoids. Below are some of the more common symptoms reported:
- Fatigue or weakness
- Changes in bowel habits that persist for more than several days
- Unexplained weight loss
- Blood in the stool
- Bleeding from the rectum
- Abdominal pain
- Abdominal cramping
Symptoms cannot be relied on for screening or diagnosis, however, both because of their similarity to other diseases and because the symptoms are a late finding in colorectal cancer, meaning there has already been significant progression.
Causes of Colorectal Cancer
Although cancer is a complex process with a variety of causative factors, on a fundamental level, it occurs due to mutations in the DNA of the affected cells. The specific gene types that appear to be involved are called oncogenes and tumor suppressor genes; oncogenes are responsible for helping cells divide and grow, and tumor suppressor genes are responsible for preventing the kind of cellular overgrowth that happens in cancer.
One of the main tumor suppressor genes involved at the beginning of cancer is the adenomatous polyposis coli (APC) gene. When this gene becomes mutated, it can no longer function as a “brake” on cellular growth and therefore overgrowth happens. It is not completely understood why these kinds of mutations happen in the first place. Diseases like familial adenomatous polyposis (FAP), a condition characterized by the development of a large number of adenomatous polyps, suggest that it can sometimes be inherited from a parent. But research suggests that these mutations may also be acquired during the course of life from exposure to a variety of risk factors.
What are the Risk Factors for Colorectal Cancer?
Scientists have found links between certain behaviors and risk factors that make someone more likely to develop colorectal cancer, although it is still unknown how these factors precisely “cause” cancer. The American Cancer Society has identified a number of these risk factors, and they are generally divided into inherent factors (those that can’t be controlled) and lifestyle factors (those that can be controlled):
- Age 50 years or older
- Some diseases, such as inflammatory bowel disease or type 2 diabetes
- Personal or family history of colorectal cancer
- Racial and ethnic background, such as African Americans and Jews of Eastern European descent
- Inherited syndromes, such as FAP or Lynch syndrome
- Heavy drinking
- Smoking tobacco
- Eating a lot of red or processed meats
- Lacking sufficient regular exercise
Treatment Options for Colorectal Cancer
Doctors use a “staging” system to describe and organize the progression of cancer and the appropriate treatments for the different levels of progression. This system runs from very early (stage 0) to very advanced (stage IV):
- Status: The cancer is confined to polyps or small tumors in the mucosal lining of the colon
- Treatment: Endoscopy or surgery to remove the polyps or tumors is standard, but a partial colectomy may also be warranted
- Status: The cancer has grown past the mucosal lining and into the wall of the colon itself, but it hasn’t spread to the lymph nodes or other parts of the body
- Treatment: Surgery is the main treatment option to remove any cancer-containing parts of the colon
- Status: The cancer has grown through the wall of the colon, but still hasn’t reached the lymph nodes
- Treatment: Both surgery and chemotherapy are typically used at this stage, depending on the nature of the spread
- Status: The cancer has spread to the lymph nodes, but not to distant body parts
- Treatment: Surgery and chemotherapy are standard, but radiation therapy may also be employed
- Status: The cancer has spread beyond the colon to other parts of the body
- Treatment: Surgery may be utilized as needed (usually palliative, to improve quality of life), but chemotherapy is the primary treatment option
Colorectal Cancer Screening
It is before cancer develops or when the cancer is still in the early (or local) stage that doctors have the best chance of treating for long-term success. For this reason, those who are 45 years or older should start talking with a qualified gastroenterologist about getting screened. If you want more information about a colorectal cancer screening, Contact Us.