Colorectal Cancer
What is Colorectal cancer?
Colorectal cancer starts in the colon or rectum, which are parts of your large intestine. This cancer usually begins as small growths called polyps on the inner lining of the colon or rectum. Most polyps are not cancerous, but some can turn into cancer over time. When cells in these areas start growing out of control, they can form tumors.
This is one of the most common cancers in the United States. It affects both men and women, usually after age 50. The good news is that colorectal cancer is highly treatable when caught early. Regular screening can even prevent it by finding and removing polyps before they become cancerous.
Understanding your risk factors and getting screened at the right time can make a real difference. Most colorectal cancers grow slowly over several years. This gives you time to catch problems early through testing and lifestyle changes.
Symptoms
Many people with early colorectal cancer have no symptoms at all. This is why screening is so important even when you feel fine. When symptoms do appear, they may include:
- Changes in bowel habits lasting more than a few days, including diarrhea or constipation
- Feeling that you need to have a bowel movement that is not relieved by doing so
- Rectal bleeding or blood in your stool
- Dark or black stools
- Cramping or abdominal pain
- Weakness and fatigue
- Unintended weight loss
- Narrow stools
These symptoms can also be caused by other conditions like hemorrhoids or infections. However, you should talk to a doctor if they last more than a week or two.
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Causes and risk factors
Colorectal cancer develops when cells in the colon or rectum develop changes in their DNA. These changes cause cells to grow and divide uncontrollably. Risk factors include being over age 50, having a family history of colorectal cancer or polyps, and having inflammatory bowel disease like Crohn disease or ulcerative colitis. People with inherited genetic syndromes like Lynch syndrome or familial adenomatous polyposis have higher risk.
Lifestyle factors play a big role in colorectal cancer risk. Eating a diet high in red and processed meats may increase risk. Being overweight, not exercising regularly, smoking, and drinking alcohol all contribute to higher risk. People with type 2 diabetes also have increased risk. A diet low in fiber and high in refined carbohydrates may make polyps more likely to form.
How it's diagnosed
Colorectal cancer is diagnosed through several types of screening tests. Colonoscopy is the most common method, allowing doctors to see inside the entire colon and rectum and remove polyps during the same procedure. Other screening options include flexible sigmoidoscopy, CT colonography, and stool-based tests that check for blood or abnormal DNA. Most guidelines recommend starting regular screening at age 45 for people at average risk.
If screening tests find something abnormal, doctors may order specialized blood tests and imaging scans. Some blood tests look for specific genetic mutations like BRAF that appear in about 10% of colorectal cancers. Other biomarkers like IGF-2 may be elevated in people with colorectal cancer. These tests help doctors understand the type of cancer and plan treatment. Talk to a doctor about which screening tests are right for you based on your age and risk factors.
Treatment options
Treatment for colorectal cancer depends on the stage, location, and specific characteristics of the cancer. Common approaches include:
- Surgery to remove cancerous polyps, tumors, or sections of the colon or rectum
- Chemotherapy using drugs to kill cancer cells or stop them from growing
- Radiation therapy to destroy cancer cells with high-energy beams
- Targeted therapy drugs that attack specific features of cancer cells
- Immunotherapy to help your immune system fight cancer cells
- Eating a plant-rich diet with plenty of fiber from vegetables, fruits, and whole grains
- Maintaining a healthy weight through regular physical activity
- Limiting red meat, processed meats, and alcohol
- Not smoking or quitting if you currently smoke
Treatment often combines several of these approaches. Your care team will create a plan based on your specific situation. After treatment, regular follow-up testing helps ensure the cancer does not come back.
Frequently asked questions
Most medical organizations recommend starting regular colorectal cancer screening at age 45 for people at average risk. If you have a family history of colorectal cancer or polyps, you may need to start screening earlier. Talk to your doctor about when you should begin based on your personal and family health history.
Many colorectal cancers can be prevented through regular screening and healthy lifestyle choices. Screening can find and remove polyps before they turn into cancer. Eating a high-fiber diet, exercising regularly, maintaining a healthy weight, limiting alcohol, and not smoking all reduce your risk. These changes work together to protect your colon health over time.
Colon cancer starts in the colon, which is the longer part of the large intestine. Rectal cancer begins in the rectum, the last several inches of the large intestine before the anus. Both are types of colorectal cancer and share many risk factors and symptoms. Treatment approaches may differ slightly based on the exact location of the cancer.
Screening frequency depends on which test you choose and your risk level. A colonoscopy is typically done every 10 years if results are normal and you have average risk. Flexible sigmoidoscopy is usually every 5 years. Stool-based tests may be done annually. Your doctor will recommend the best schedule for your situation.
About 10% of colorectal cancers have a BRAF mutation, which is a change in a specific gene. Cancers with BRAF mutations may be more aggressive and respond differently to certain treatments. Testing for this mutation helps doctors choose the most effective chemotherapy options. It also provides information about prognosis and helps guide personalized treatment plans.
Most colorectal cancers are not inherited, but family history does matter. About 5 to 10% of cases are linked to inherited genetic syndromes like Lynch syndrome or familial adenomatous polyposis. If you have multiple close relatives with colorectal cancer, especially if they were diagnosed before age 50, genetic counseling may be helpful. Even without inherited syndromes, having family members with colorectal cancer increases your risk.
Eating plenty of vegetables, fruits, and whole grains provides fiber that protects your colon. Regular physical activity, at least 150 minutes per week, significantly lowers risk. Maintaining a healthy body weight matters because obesity increases risk. Limiting red and processed meats, avoiding excessive alcohol, and not smoking all help prevent colorectal cancer.
Some specialized blood tests can help doctors understand colorectal cancer once it has been found through screening. BRAF mutation analysis checks for genetic changes in cancer cells. IGF-2 is a hormone that may be elevated in people with colorectal cancer. These tests are not used for initial screening but help guide treatment decisions and monitor disease.
If your doctor finds a polyp during a colonoscopy, they will usually remove it right away. The polyp is then sent to a lab to check whether it contains any cancer cells. Most polyps are benign, meaning they are not cancerous. Removing polyps prevents them from potentially turning into cancer later. Your doctor will tell you when you need your next colonoscopy based on what they found.
Yes, research shows that diet plays a significant role in colorectal cancer risk. Eating processed meats like bacon and hot dogs regularly increases risk. Diets high in red meat also raise risk. In contrast, eating plenty of fiber from plant foods helps protect your colon. Foods rich in vitamins, minerals, and antioxidants support healthy cell function and may prevent the DNA changes that lead to cancer.