Colon cancer is the third most common cancer diagnosed in men and women in the U.S. While treatments for colon cancer have improved, it remains the second leading cause of cancer death in the U.S. 
However, with regular screenings, colon cancer is preventable. Here’s everything you need to know about colon cancer symptoms, screenings, treatments, and risks.
How Does Colon Cancer Develop?
Colon cancer begins with malignant cells in the colon or large intestine. In the body’s digestive system, food passes through the stomach to the small intestine, then to the colon before expelling through the rectum. The colon removes fluids and nutrients from food, solidifying your body’s waste.
For colon cancer to develop, mutated cells divide even when they’re not needed, causing a buildup of cells that create polyps along the walls of the colon. As the cells continue to reproduce, polyps can grow and multiply, causing digestive issues and in some cases, becoming cancerous. 
Polyps cause few symptoms, if any. The lack of symptoms in the early stages of colon cancer makes regular screenings essential in preventing colon cancer from developing by removing polyps before they become cancerous.
Colon Cancer Screening
There are several tests to screen for colon cancer during the early stages of the disease before symptoms begin. In addition, some colon cancer screening methods allow physicians to remove polyps, serving as a diagnostic and preventative tool. Physician-approved screening tests for colon cancer include:
Stool tests check for tiny amounts of blood in fecal matter, indicating the presence of polyps and colorectal cancers that bleed. In a stool test, patients use a kit to collect stool samples, which are then returned to their doctor to test for blood.
Patients who receive a positive result from their stool test are sent to have a colonoscopy to confirm findings and remove polyps.
A sigmoidoscopy uses a flexible, lighted tube that contains a camera for viewing and a tool to remove tissue called a sigmoidoscope. A physician inserts this tool into the rectum through the anus and sigmoid colon while air is pumped into the space so the doctor can view the colon lining.
This procedure allows physicians to remove any abnormal growths so they can be biopsied to analyze for cancerous cells.
A colonoscopy examines the rectum and the entirety of the colon using a colonoscope, a flexible tube with lighting, a camera, and a tool to remove tissue. A colonoscopy is similar to a sigmoidoscopy. However, this procedure views the entire colon and rectum.
Abnormal growths can be removed during a colonoscopy and analyzed later for cancerous cells. 
When Should Colon Cancer Screening Begin?
While the medical guidelines on colon cancer screening vary slightly, most expert medical groups recommend that patients at average risk of developing colon cancer begin screening between the ages of 45 and 50.
Patients with a higher risk of developing colon cancer may begin colon cancer screenings earlier and have them more frequently. Patients of average risk should undergo stool testing every three years, a sigmoidoscopy every five to ten years, or a colonoscopy every ten years.
What Are the Risk Factors of Developing Colon Cancer?
Several risk factors contribute to a patient’s risk of developing colon cancer. These include:
- Age: most patients diagnosed with colon cancer are over 50
- Race: African-Americans are at greater risk
- Personal history of colorectal cancer or polyps
- Chronic inflammatory diseases of the intestines
- Inherited gene mutations
- Family history of colon cancer
- A low-fiber, high-fat diet
- Sedentary lifestyle
- Heavy alcohol use
- Previous radiation therapy for cancer
Patients with these risk factors should consult their physicians to determine when to begin colon cancer screening and the type of screening that best meets their needs.
What Are the Symptoms of Colon Cancer?
In colon cancer’s early stages, many patients experience no symptoms. If a patient does have symptoms from colon cancer, they include:
- Digestive issues, such as constipation, diarrhea, or oddly shaped stool
- Feeling the urge to have a bowel movement
- Pain or discomfort during a bowel movement
- Rectal bleeding
- Abdominal pain or discomfort
- Weight loss
- Abdominal bloat and gassiness
- Frequent urinary tract infections
- Nausea or vomiting
Colorectal cancers may bleed into the digestive tract, causing patients to see blood in their stool that appears dark brown or black. If the blood loss continues, a patient may experience a low red blood cell count, known as anemia. Anemia can be an early sign of colon cancer. 
What Do the Stages of Colon Cancer Mean?
After a cancer diagnosis, physicians then determine whether the cancer has spread to classify how much cancer is in the body, the seriousness of the diagnosis, and the best course of treatment. This process, called staging, takes three main factors into account:
- The size of the tumor
- Whether cancer has spread to nearby lymph nodes
- If cancer spread to distant areas of the body
A physician classifies cancer into one of four main stages through these factors. The earliest stage of cancer is stage 0.
Stage 1 colon cancer has not spread beyond the layers of the colon wall.
When colon cancer reaches stage 2, the cancer may have reached the edges of the colon wall or just beyond but hasn’t spread into other tissues, lymph nodes, or organs. At stage 3, colon cancer has spread to nearby tissues, organs, or lymph nodes but not distant sites. Stage 4 colon cancer has spread to a distant organ. 
How Can I Reduce My Risk of Developing Colon Cancer?
Even those at a higher risk of developing colon cancer can lower their risk through lifestyle changes. These include:
- Increasing your consumption of nutrient-rich fruits, vegetables, and whole grains
- Quitting smoking
- Drinking alcohol in moderation or not at all
- Maintaining a healthy weight
- Exercising regularly
Adjusting your diet and lifestyle to prevent colon cancer and undergoing regular preventative screenings as directed by your physician can lower your risk of developing colon cancer.