Colon and rectal cancer, collectively known as colorectal cancer, develop when cells grow out of control in the colon or rectum, sections of the large intestine. Cancer may also arise elsewhere and spread to the intestines.

Colorectal cancer is the second leading cause of cancer death in the United States, after lung cancer. Although cases and deaths have been declining for several decades—thanks to screening, lifestyle changes and better treatment—incidence is rising among younger adults.

Colorectal cancer mostly occurs among people over 50. African Americans have the highest rate in the United States. Other unchangeable risk factors include genetics (for example, an inherited condition called Lynch syndrome), family history and inflammatory bowel disease.

Lifestyle factors also play a role. Obesity, lack of physical activity, smoking, alcohol and a diet high in red and processed meats increase the risk for colo­rectal cancer, while a diet high in fruits, vegetables and whole grains has a protective effect.

Many people with colorectal cancer don’t develop symptoms until the later stages of disease, but screening can catch cancer early, when it’s easier to treat. Fecal tests look for blood or DNA changes in a stool sample; these tests can be done at home. Visualization tests involve viewing either the entire colon (colonoscopy) or the lower part of the colon and rectum (sigmoidoscopy) to detect and remove polyps, or abnormal precancerous growths.

As of 2021, U.S. guidelines recommend that people at average risk should be screened for colorectal cancer starting at age 45 (down from age 50 in the previous guidelines). However, people at higher risk may benefit from starting screening sooner. Both fecal tests and visualization tests are recommended—the most effective test is the one that gets done.

Treatment for colorectal cancer depends on the location, size and number of tumors and whether the cancer has spread to nearby lymph nodes or other parts of the body. Precancerous growths and localized tumors in the colon and rectum can often be surgically removed. More advanced cancer may require removal of part of the intestine. Radiation may be used to shrink tumors, which can help relieve pain and other symptoms.

Systemic therapy is administered by mouth or via IV infusion. Neoadjuvant therapy is given before surgery to shrink tumors and make them easier to remove, while adjuvant therapy is given after surgery to kill off any remaining malignant cells and reduce the risk of recurrence.

Traditional chemotherapy works by killing fast-growing cells, including cancer cells. Many targeted therapies work by interfering with tumor development. Erbitux (cetuximab) and Vectibix (panitumumab), for example, block the activity of EGFR, a protein involved in cell growth, while Avastin (bevacizumab) and Cyramza (ramucirumab) target VEGF, a protein that promotes the development of blood vessels that feed tumors. Immunotherapy helps the immune system fight cancer. The checkpoint inhibitors Keytruda (pembrolizumab), Opdivo (nivolumab) and Yervoy (ipilimumab) are used to treat colorectal cancer with specific genetic characteristics. Another checkpoint inhibitor, Jemperli (dostarlimab), has shown promising results for rectal cancer in a clinical trial.

Colorectal cancer treatment continues to evolve, and several new therapies are under study. Ask your doctor whether a clinical trial might be a good option for you.