Colorectal Cancer Overview
The colon is also known as the large intestine. The large intestine is about five feet long and is a giant, powerful, muscular tube. The colon is considered the last part of the digestive process and helps remove water, salt, and some nutrients from the food we eat. By the time food enters the colon, it is liquified. Once this liquid hits the large intestine, water is absorbed by the colon, and solid waste is formed. Beneficial bacteria that line the colon help break down the material further before the colon moves the material into the rectum. The material, now known as stool, passes through the rectum and exits the body.
Colorectal cancers usually begin as an uncontrolled growth of cells in the inner lining of the colon or rectum. Growths in the colon or rectum are commonly referred to as polyps. Over time these growths, or polyps, can become cancerous. There are three different types of polyps that each have varying chances of turning into a cancerous mass. These polyps are:
- Adenomatous polyps. These growths can eventually turn into cancerous tumors. Adenomatous polyps are often referred to as “pre-cancerous” polyps. These polyps come in three distinct types that include tubular, villous, and tubulovillous growths.
- Hyperplastic polyps or inflammatory polyps. These growths can be relatively common and are generally benign. If a hyperplastic polyp grows to be more than one centimeter in size, physicians will generally consider more frequent colorectal cancer screenings.
- Sessile serrated polyps or SSP and traditional serrated adenomas or TSA. These types of growths have a higher risk of turning cancerous, similar to adenomatous polyps.
Cancer can form in these polyps and then grow into the wall of the colon and rectum as well as spread to other areas of the body. Most colorectal cancers start in the inner layer of the intestine, the mucosa, and then grow outward. Cancer cells can also grow into the vast network of blood vessels and lymph vessels that line the colon. Although one type of colorectal cancer is much more common than the others, there are different types of colorectal cancers. They include:
- Adenocarcinom. Most colorectal cancers are adenocarcinomas. This form of cancer begins in the cells that make mucus. Mucus is used to lubricate the colon and rectum.
- Carcinoid tumors. The large intestine has unique hormone-making cells which can play host to cancer cells. These tumors are less common than adenocarcinomas.
- Gastrointestinal stromal tumors or GISTs. Cells called the interstitial cells of Cajal are found all along the walls of the digestive tract, including the colon. Although not commonly found in the colon itself, when these tumors form, they can turn cancerous.
- Lymphomas. Lymphomas start in the lymph nodes and are considered cancers of the immune system cells. However, lymphomas can also start in the colon, rectum, and other organs that contain lymph tissue.
- Sarcomas. Although rare, sarcomas begin as a growth of cells in the blood vessels, muscle tissue, or other connective tissues in the walls of the colon or rectum.
Symptoms Associated with Colorectal Cancer
Unfortunately, colorectal cancer can be difficult to detect in its early stages. That is why so many physicians recommend routine screening for the disease. Often touted as embarrassing and uncomfortable, colorectal screenings are essential tools for catching the condition early and offer the best potential for swift treatment options and a good prognosis for recovery.
Although the American Cancer Society has a colorectal screening guideline, those with elevated risk factors should talk to their doctor about how often they should be screened.
Symptoms of colorectal cancer may include:
- Rectal bleeding
- Bloody stool
- Abdominal pain
- Cramping, gas, or lower abdominal discomfort
- Changes in bowel habits, such as persistent constipation or diarrhea
- Changes in the consistency of stool
- Fatigue
- Unexplained weight loss
Causes of Colorectal Cancer
At this time, the causes of colorectal cancer are not well understood. Although there are factors that result in an increase in the likelihood of developing colorectal cancer, it is not clear how the factors ultimately contribute to the development of the disease.
Cancer is often the result of gene mutations, and some inherited gene mutations can be linked to the development of colorectal cancer. Although only a small fraction of colorectal cancers are considered to be genetic, some gene mutations have been linked to the development of the disease. Familial adenomatous polyposis (FAP), Gardner syndrome, Lynch syndrome, and Peutz-Jeghers syndrome all have genetic components that may increase the likelihood of developing colorectal cancer.
Risk Factors of Colorectal Cancer
Other than genetic components, certain risk factors may elevate an individual’s chances of developing colorectal cancer. Some of these risk factors include lifestyle choices related to diet and exercise. Other risk factors may not be changed, such as a family history or gender. The risk factors can include:
- Aging
- African-American heritage
- Being a male
- Genetic factors
- Chronic inflammatory intestinal conditions
- A high-fat, low-fiber diet
- Low levels of vitamin D in the blood
- Inactivity or sedentary lifestyle
- Obesity
- Diabetes
- Smoking
- Alcohol use
Colorectal Cancer Survival Rates
The American Cancer Society estimates that in 2021, there will be close to 104,270 new cases of colon cancer in the United States and 45,230 new cases of rectal cancer. When it comes to the average five-year survival rate for those diagnosed with the disease, it is important to remember that the stage at which the disease is caught and available treatment options can all play a role in a patient’s prognosis. In general, almost 65 percent of people diagnosed with colorectal cancer will live five years or more after being diagnosed. Those who are diagnosed early, while the cancer is localized and confined to the colon, have a five-year survival rate of 90 percent. Once the cancer is distant, meaning it has metastasized and spread, the five-year survival rate stands at just under 15 percent.