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Shannon Shelton Miller

Shannon Shelton Miller is an award-winning writer and journalist who specializes in education, parenting, culture and diversity, sports, and health and beauty articles. She has been published in the New York Times, the Washington Post,, Slate, InStyle and the Huffington Post.

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Colorectal Cancer 101

Understand the basics of colorectal cancer, who’s at risk and how you can increase your chances of survival if you develop the disease

Conditions & Treatments

Medically reviewed by Robert Nagourney, M.D.

Colorectal cancer begins in the colon or the rectum, and is also called colon or rectal cancer, depending on where cancer cells are first found.

The colon is the part of the large intestine that food moves through, and the rectum is the lower part of the colon where waste is stored before it leaves the body, through the anus.

  • An estimated 106,000 new cases of colon cancer and 44,850 new cases of rectal cancer will be diagnosed in 2022.
  • Risk factors include getting older, diet, obesity, drinking too much alcohol and a family history of cancer.
  • Men have a higher rate of colon cancer than women (30% higher) and an even higher rate of rectal cancer than women (60%). Colon cancer is more common in non-Hispanic Black populations and less common in Asian populations.
  • When colorectal cancer develops, tumors form on the surface of the colon and rectum and grow into small masses known as polyps. If found early, the polyps can be removed, but if they are not detected early, they can move deeper into tissues, invade lymph nodes and ultimately spread to other parts of the body.
  • If you have a family history of colorectal cancer or other risk factors, including having had another cancer, talk to your healthcare provider (HCP) to see what age you should get screened. It could be earlier than 45.
  • Lifestyle and diet can reduce your risk of developing colorectal cancer. People can lower their risk by decreasing weight, lowering alcohol intake, quitting smoking, and decreasing the amount of processed food and red meat they eat. Regular exercise also helps reduce the risk of developing colorectal cancer.
  • Colorectal cancer may not cause symptoms at first, but patients should see their HCP if they notice symptoms such as diarrhea, constipation or narrowing of the stool that lasts for more than a few days; rectal bleeding; blood in their stool; cramping or abdominal pain; weakness and fatigue; or unexplained weight loss.
  • There are several ways to screen for colorectal cancer, including detecting blood in the stool, measuring DNA changes in the stool, and direct examination of the colon and rectum using an instrument called a colonoscope. This instrument is inserted into the rectum and is used to examine the colon tissue. It’s also used to biopsy or remove any suspicious areas.
  • Colorectal cancer treatment is determined by its stage at diagnosis. Early-stage cancer with no evidence of deep invasion or spread can be treated with surgery alone. Once the disease spreads to lymph nodes, patients are given some type of treatment, such as chemotherapy or immunotherapy, after surgery to lower the risk of it coming back.
  • Patients who have advanced disease that has spread to distant organs like the lungs or liver should begin receiving treatment immediately. A patient’s healthcare team will decide the best course of treatment.
  • For rectal cancer, patients often receive chemotherapy and radiation before surgery. This process is known as total neoadjuvant therapy or TNT. If those treatments remove the cancer, some patients might not need surgery at all. Even when surgery is needed,TNT can help improve patient outcomes and survival rates from cancer.
  • Researchers are working to improve future colorectal cancer treatments by measuring each patient's cancer cells to determine how well their current treatments worked and make adjustments if needed. HCPs usually remove the cancer cells during a biopsy or before surgery.
  • Colorectal cancer doesn’t have to be a death sentence. Making healthy lifestyle changes, getting screened regularly and working closely with your healthcare team to develop a treatment plan can increase your chances of long-term survival from the disease.

This resource was created with support from Merck.

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