Colorectal cancer, describing both colon and rectal cancer, is the third leading cause of cancer-related deaths in the US. Experts estimate that in 2022 over 100,000 new cases of colon cancer and almost 45,000 new cases of rectal cancer will be diagnosed. About 50,000 deaths due to colon and rectal cancers among Americans will occur in 2022.
Colon cancer causes and risk factors
Colorectal cancer is caused by a cancerous growth of the cells lining the colon or rectum. Cancer develops when healthy cells develop mutations within their DNA. In normal conditions, cells grow and divide in a way that supports a healthy function of the body. However, when the DNA is damaged, the cells become cancerous, divide abnormally, and form tumors. As cancer progresses, the tumor spreads and destroys the nearby tissue, later traveling to other body parts, creating metastasis.
Colon cancer risk factors:
- Having colon polyps or family members with colon polyps or colon cancer.
- Diseases affecting the colon like Crohn’s disease or ulcerative colitis, as well as diabetes.
- Advanced age: While colon cancer can occur early in life, it is more common in those aged 50 or older.
- Gender: Colorectal cancer is slightly more common among men than women.
- Inherited diseases like familial adenomatous polyposis and Lynch syndrome.
There are also colon cancer risk factors you can, to some extent, control. They include:
- Diet may play a role. For example, eating red meat in excess, processed foods, refined sugar, and not eating enough dietary fiber may contribute to the risk.
- Lifestyle habits. Based on research studies, physical inactivity, excess body weight, especially belly fat, consuming alcohol in excess, and smoking early in life are risk factors for colon cancer.
Colon cancer symptoms
Many people do not experience any symptoms in the early stages of cancer. When symptoms develop, they vary based on the location of cancer in the intestine and the size of the tumor.
- The most common symptoms are bleeding when passing stool along with significant fatigue and weakness.
- A change in bowel movement, either with constipation, diarrhea, or different consistency of the stool.
- Pain and discomfort in the abdomen.
- A sensation that the bowel doesn’t empty after a bowel movement.
- Significant weight loss (without dieting).
- Vomiting, severe cramps, and a swollen abdomen may occur when the cancerous tumor causes bowel obstruction.
Colon cancer diagnosis
If the symptoms suggest colon cancer, a doctor will order several tests, including a colonoscopy, CT scan of the abdomen, blood tests, and chest x-ray.
There are special blood tests evaluating CEA or carcinoembryonic antigen. Tracking CEA levels over time can help evaluate the prognosis and how cancer responds to the treatment.
Because colon cancer is a common condition, screening tests for colon cancer are recommended at age 45 or earlier if there are risk factors. Screening tests include stool tests, a colonoscopy every 10 years, CT scans, and CT colonography.
Colon cancer treatment
The treatment depends on the cancer stage and may involve surgery, chemotherapy, and radiation therapy. There are also newer treatments available.
The stages of cancer are labeled with Roman numbers 0, I, II, III, and IV. Stage IV is when it spreads to other parts of the body and is the most advanced form of cancer.
- Minimally invasive surgery is recommended for the early stages. Small cancerous polyps can be removed during a colonoscopy.
- More advanced forms of cancer require partial colectomy, which involves the removal of the part of the colon affected by cancer. Lymph nodes affected by cancer are also removed. If cancer spreads to the liver, the doctor may recommend surgery to remove the cancerous tumor.
- Chemotherapy is typically recommended after surgery if the cancer is advanced and has already spread to the lymph nodes and other organs. In some cases, chemotherapy can be used before surgery to shrink the tumor. Chemotherapy can be combined with radiation therapy. Radiation therapy can be used alone when surgery is not an option.
- Newer treatment options include targeted drug therapy and immunotherapy. In the case of targeted drug therapy, the drug targets specific proteins that occur in cancer cells. Immunotherapy is based on drugs that use the immune system to destroy cancer cells and is usually recommended in advanced cases.
- Palliative care involves a team of healthcare professionals, and the treatments focus on pain relief and overall improvement of quality of life. Palliative surgery is considered when removing the cancerous tumor is not possible, to remove a bowel obstruction.
The relative survival rate compares individuals with a certain type and stage of cancer to an individual without colon cancer, from the general population. For example, the relative five-year survival rate is over 90% if cancer did not spread outside of the colon or rectum, which is localized cancer. The 5-year relative survival rate for colon cancer drops below 20% if cancer spreads to the liver, lungs, or distant lymph nodes (distant cancer). Therefore, detecting colon cancer early is essential.
Colon cancer prevention
While some risk factors, such as age or inherited diseases, can’t be prevented, you can modify several risk factors. Consider improving your lifestyle to reduce the risk of colon cancer.
- Diet. Adopt a healthy diet with plenty of vegetables, fruits, whole grains, legumes, healthy oils from olive oil, herbs, and spices. Limit red meat and eliminate processed foods. The Mediterranean diet was protective against colorectal cancer in some studies.
- Stay active. Aim for 30-45 minute workouts most days of the week. Most people benefit from a combination of aerobic exercise and weight training. Regular exercise helps reduce the risk of colon cancer and also colon polyps.
- Weight management. A healthy diet combined with regular exercise can help you lose extra pounds and maintain a healthy weight. If you need to lose a lot of weight, make sure you lose it slowly, with the help of a dietician or nutritionist.
- If you have diabetes, keep it well controlled with diet and medication.
- Talk to the doctor about getting screening tests after age 45, or earlier if you have risk factors.