Definition
Rectal cancer is cancer that begins in the rectum. The rectum is the last several inches of the large intestine. It starts at the end of the final segment of your colon and ends when it reaches the short, narrow passage leading to the anus.
Cancer inside the rectum (rectal cancer) and cancer inside the colon (colon cancer) are often referred to together as “colorectal cancer.”
According to the American Cancer Society, colorectal cancer disproportionately affects the Black community, where the rates are the highest of any racial/ethnic group in the US. Blacks are about 20% more likely to get colorectal cancer and about 40% more likely to die from it than most other groups.
Symptoms
Signs and symptoms of rectal cancer include:
- A change in bowel habits, such as diarrhea, constipation or more-frequent bowel movements
- Dark maroon or bright red blood in stool
- Narrow stool
- A feeling that your bowel doesn’t empty completely
- Abdominal pain
- Unexplained weight loss
- Weakness or fatigue
Diagnosis
Rectal cancer can be found during a screening test for colorectal cancer or a diagnosis can be based on your symptoms.
Causes
Rectal cancer begins when healthy cells in the rectum develop changes (mutations) in their DNA. A cell’s DNA contains the instructions that tell a cell what to do.
The changes tell the cells to grow uncontrollably and to continue living after healthy cells would die. The accumulating cells can form a tumor. With time, the cancer cells can grow to invade and destroy healthy tissue nearby. Cancerous cells may also break away and travel (metastasize) to other parts of the body.
In many rectal cancers, it’s unclear what causes the mutations that cause the cancer to form.
Gene mutations may be passed from parents to children and increase the risk of colorectal cancer. However, these mutations are involved in only a small percentage of rectal cancers. Some genes linked to colorectal cancer increase the risk of developing the disease, but they don’t make it inevitable.
The following are genetic colorectal cancer syndromes are:
- Lynch syndrome. Lynch syndrome, also known as hereditary nonpolyposis colorectal cancer (HNPCC), increases the risk of colon cancer and other cancers. People with Lynch syndrome tend to develop colon cancer before age 50.
- Familial adenomatous polyposis (FAP). FAP is a rare disorder that causes thousands of polyps in the lining of your colon and rectum. People with untreated FAP have a significantly increased risk of developing colon or rectal cancer before age 40.
Either of these syndromes other, rarer inherited colorectal cancer syndromes can be detected by genetic testing. If you have a family history of colon cancer, you should talk with your doctor about your risk factors.
Risk Factors
Factors that may increase the risk of rectal cancer are the same as those that increase the risk of colon cancer. Colorectal cancer risk factors include:
- Older age. Although colorectal cancer can be diagnosed at any age, most people with this type of cancer are older than 50. However, the rates of colorectal cancer in people younger than 50 have been increasing, but doctors aren’t sure why.
- African-American descent. Blacks have a greater risk of colorectal cancer than people of European ancestry.
- A personal history of colorectal cancer or polyps. Your risk of colorectal cancer is higher if you’ve already had rectal cancer, colon cancer or adenomatous polyps.
- Inflammatory bowel disease. Chronic inflammatory diseases of the colon and rectum, such as ulcerative colitis and Crohn’s disease, increase your risk of colorectal cancer.
- Inherited syndromes that increase rectal cancer risk. Genetic syndromes passed through generations of your family can increase your risk of colon and rectal cancer, including FAP and Lynch syndrome.
- Family history of colorectal cancer. You’re more likely to develop colorectal cancer if you have a parent, sibling or child with colon or rectal cancer.
- Eating a diet low in vegetables. Colorectal cancer is often associated with a diet low in vegetables and high in red meat, especially when the meat is charred or well done.
- Too little exercise. If you’re inactive, you’re more likely to develop colorectal cancer. By getting regular physical activity, you can reduce your risk of cancer.
- Diabetes. People with poorly controlled type 2 diabetes may have an increased risk of colorectal cancer.
- Obesity. Obese people have an increased risk of colorectal cancer in comparison to people who are considered to be at a healthy weight.
- Smoking. People who smoke may have an increased risk of colorectal cancer.
- Drinking alcohol. Regularly drinking more than three alcoholic beverages a week may increase your risk of colorectal cancer.
- Radiation therapy for previous cancer. Radiation therapy directed at the abdomen to treat previous cancers may increase the risk of colorectal cancer.
Treatment
In the past, long-term survival was uncommon for people with rectal cancer, even if they had extensive treatment. However, treatment advances over the last few decades have caused rectal cancer survival rates to greatly improve.
Rectal cancer treatment often involves a combination of therapies. When possible, surgery is used to cut away the cancer cells. Other treatments, such as chemotherapy and radiation therapy, may be used after surgery to kill any cancer cells that remain and reduce the risk that your cancer returns.
If surgeons are concerned that the cancer can’t be removed completely without hurting nearby organs and structures, your doctor may suggest a combination of chemotherapy and radiation therapy as your initial treatment. These combined treatments can shrink the cancer making it easier to remove during an operation.
Prevention
To reduce your risk of colorectal cancer, consider trying to:
- Talk to your doctor about cancer screening
- Exercise most days of the week
- Eat a variety of fruits, vegetables and whole grains
- Maintain a healthy weight
- Stop smoking
- Drink alcohol in moderation
Although rectal and colon cancers are similar in many ways, their treatments are quite different. This is mainly because the rectum sits in a tight space, barely separated from other organs and structures. The tight space can make surgery to remove rectal cancer complex.