Rectal Cancer Causes and Risk Factors

Rectal cancer begins in the rectum, the last several inches of the large intestine (colon) near the anus. Most rectal tumors begin as benign growths (polyps) that slowly progress over time. The progression can take up to several years, and most rectal polyps do not become cancerous.

The first warning sign of rectal cancer may be a change in bowel habits, such as persistent diarrhea or constipation, or rectal bleeding. However, precancerous polyps and early-stage rectal cancer can often be detected during a routine screening test, such as a colonoscopy, before any noticeable symptoms develop.

Collectively known as colorectal cancer, colon cancer and rectal cancer develop in the same way and share many risk factors; however, colon cancer is more common. As with most types of cancer, an early diagnosis and prompt treatment are essential to achieve the best possible outcome and quality of life.

"When you go to the doctors, have faith in them and that they're going to do the best thing for you and have your best interests at heart. And that's exactly what every doctor here at Moffitt has done."

Melissa, Rectal Cancer Survivor

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What causes rectal cancer?

Rectal cancer develops when cells in the lining of the rectum undergo harmful DNA changes. Unlike healthy cells, which reproduce in an orderly fashion and die at the end of their normal lifespan, damaged cells divide rapidly, live longer than they should and form polyps in the rectum. Rectal polyps can become cancerous and may do so at different rates depending on their size and cellular makeup.

Through extensive research, scientists have learned that the cellular mutations that lead to the development of rectal cancer can be inherited or acquired. While the precise sequence of genetic changes can vary, it usually involves alterations in several genes that regulate cell growth, cell division and programmed cell death (apoptosis). Common genetic mutations associated with rectal cancer include changes in the APC gene, KRAS gene and p53 tumor suppressor gene.

What are the risk factors for rectal cancer?

Risk factors are characteristics, behaviors and exposures that can increase the likelihood of developing rectal cancer, although they do not directly cause it. While some rectal risk factors can be controlled, others cannot.

Rectal cancer risk factors that can be controlled

By making healthy lifestyle changes, it may be possible to control certain rectal cancer risk factors, such as:

• Poor nutrition – A diet high in red and processed meats and low in fruits, vegetables, and fiber is associated with an increased risk of rectal cancer.
• Physical inactivity – A sedentary lifestyle can increase the risk of rectal cancer, while regular exercise can help reduce it.
• Obesity – Carrying excess body weight is a risk factor for many potentially serious medical conditions, including rectal cancer.
• Smoking – Tobacco use is a significant risk factor for most types of cancer, including rectal cancer.
• Alcohol consumption – Excessive consumption of alcoholic beverages has been linked to rectal cancer.

Rectal cancer risk factors that cannot be controlled

Certain rectal cancer risk factors cannot be controlled, such as:

• Advanced age – Most rectal cancers are diagnosed after age 50.
• Family history – Individuals with a close family member who was diagnosed with colorectal cancer are at high risk for rectal cancer.
• Personal history – Individuals who were previously diagnosed with an inflammatory bowel disease, such as ulcerative colitis or Crohn's disease, benign colorectal polyps, colon cancer or anal cancer have a heightened risk of developing rectal cancer.
• Inherited cancer predisposition syndromes – Certain genetic conditions, such as familial adenomatous polyposis (FAP) and Lynch syndrome, can increase the risk of developing rectal cancer.

Can rectal cancer be prevented?

Rectal cancer cannot be prevented. However, certain protective measures can be taken to manage the controllable risk factors—such as diet, physical inactivity and smoking—and lower the risk.

Overall, the most effective way to prevent rectal cancer is to have regular medical checkups and routine screening tests beginning around age 45. Colorectal cancer screening can detect precancerous polyps so they can be removed before they progress and become cancerous. In this way, colorectal cancer can be prevented. Individuals who have a personal or family history of colorectal cancer or an inherited cancer predisposition syndrome may benefit from more frequent screenings and possibly other preventive measures recommended by a physician.

Benefit from world-class care at Moffitt Cancer Center

The nationally recognized scientists and clinicians in Moffitt’s Gastrointestinal Oncology Program are continually working to gain a better understanding of rectal cancer causes and risk factors. As a National Cancer Institute-designated Comprehensive Cancer Center, Moffitt is renowned for its scientific leadership, groundbreaking research, robust clinical trials program and bench-to-bedside approach. Our goal is to quickly translate our lab discoveries into the latest treatment options for our patients.

If you would like to learn more about rectal cancer causes and risk factors, you can request an appointment with a specialist in our Gastrointestinal Oncology Program by calling 1-888-663-3488  or submitting a new patient registration form online. We do not require referrals.