Rectal cancer is cancer that starts in the rectum – the last section of the large intestine (the colon). Screening tests are important for diagnosing colon and rectal cancers early.
Rectal Cancer Overview
Rectal cancer is a type of cancer that occurs in the cells in the rectum — the last section of the large intestine (colon), which is the lower part of your digestive system. During digestion, food moves through the stomach and small intestine into the colon. The colon absorbs water and nutrients from the food and stores waste matter (stool). Stool moves from the colon into the rectum before it leaves the body.
Rectal cancer is often grouped together with colon cancer, and together they are called colorectal cancer.
Rectal cancer most often begins in the cells that line the inside of the rectum. Rectal cancer often first forms as precancerous polyps.
Many cases of colorectal cancer have no symptoms. If symptoms are present, they may include blood in the stool, diarrhea, constipation or other changed in bowel habits, and weight loss for no known reason.
Colorectal cancer is the third most common type of cancer in men and women in the United States. It is a leading cause of cancer death, but deaths from colorectal cancer have decreased in recent years with the widespread use of regular screenings, including colonoscopies and fecal occult blood tests, which check for blood in the stool.
Rectal Cancer Symptoms
Many people with colorectal cancer experience no symptoms in the early stages of the disease. When symptoms appear, they will likely vary, depending on the cancer's size and location in your large intestine.
Signs and symptoms of colorectal cancer include:
- diarrhea or constipation
- a feeling that your bowel does not empty completely
- blood (either bright red or very dark) in your stool
- stools that are narrower than usual
- frequent gas pains or cramps, or feeling full or bloated
- weight loss with no known reason
- nausea or vomiting
Rectal Cancer Causes
In most cases, the cause of colorectal cancer is not clear. Doctors know that colorectal cancer occurs when healthy cells in the colon become altered. Healthy cells grow and divide in an orderly way to keep your body functioning normally. But when a cell is damaged and becomes cancerous, cells continue to divide — even when new cells are not needed. These cancer cells can invade and destroy normal tissue nearby, and cancerous cells can travel to other parts of the body.
Factors that may increase your risk of colorectal cancer include:
- older age. The majority of people diagnosed with colon cancer are older than 50 years. Colorectal cancer can occur in younger people, but it occurs much less frequently.
- African-American race. African-Americans have a greater risk of colorectal cancer than do people of other races.
- a personal history of colorectal cancer or polyps. If you have already had colon cancer or adenomatous polyps, you have a greater risk of colorectal cancer in the future.
- inflammatory intestinal conditions. Chronic inflammatory diseases of the colon, such as ulcerative colitis and Crohn's disease, can increase your risk of colorectal cancer.
- inherited syndromes that increase colorectal cancer risk. Genetic syndromes passed through generations of your family can increase your risk of colorectal cancer. These syndromes include familial adenomatous polyposis and hereditary nonpolyposis colorectal cancer, which is also known as Lynch syndrome.
- family history of colorectal cancer and colon polyps. You're more likely to develop colorectal cancer if you have a parent, sibling or child with the disease. If more than one family member has colorectal cancer or rectal cancer, your risk is even greater. In some cases, this connection may not be hereditary or genetic. Instead, cancers within the same family may result from shared exposure to an environmental carcinogen or from diet or lifestyle factors.
- low-fiber, high-fat diet. Colon cancer and rectal cancer may be associated with a diet low in fiber and high in fat and calories. Research in this area has had mixed results. Some studies have found an increased risk of colorectal cancer in people who eat diets high in red meat. Diets high in vegetables, fruits, and whole grains have been linked with a decreased risk of colorectal cancer, but fiber supplements do not seem to help. It's not clear if other dietary components (for example, certain types of fats) affect colorectal cancer risk.
- a sedentary lifestyle. If you are inactive, you are more likely to develop colorectal cancer. Getting regular physical activity may reduce your risk of colorectal cancer.
- diabetes. People with diabetes and insulin resistance may have an increased risk of colorectal cancer.
- obesity. People who are very overweight or obese have an increased risk of colorectal cancer and an increased risk of dying of colorectal cancer when compared with people considered normal weight.
- smoking. People who smoke cigarettes may have an increased risk of colorectal cancer.
- alcohol. Heavy use of alcohol may increase your risk of colorectal cancer.
- radiation therapy for cancer. Radiation therapy directed at the abdomen to treat previous cancers may increase the risk of colorectal cancer.
Rectal Cancer Diagnosis
Regular screening can often find colorectal cancer early, when it is most likely to be curable. In many people, screening can also prevent colorectal cancer altogether. This is because some polyps, or growths, can be found and removed before they have the chance to turn into cancer.
Tests used to screen for colorectal cancers include:
- guaiac-based fecal occult blood test (gFOBT) and fecal immunochemical test (FIT). Samples of stool (feces) are checked for blood, which might be a sign of a polyp or cancer.
- stool DNA test. A sample of stool is checked for certain abnormal sections of DNA (genetic material) from cancer or polyp cells.
- sigmoidoscopy. A flexible, lighted tube is put into the rectum and lower colon to check for polyps and cancer.
- colonoscopy. A longer, flexible tube is used to look at the entire colon and rectum.
- double contrast barium enema. This is an x-ray test of the colon and rectum.
- CT colonography (virtual colonoscopy). This is a type of CT scan of the colon and rectum.
gFOBT, FIT, and stool DNA testing mainly find cancer, but they can also find polyps.
Sigmoidoscopy, colonoscopy, double contrast barium enema, and CT colonography are good at finding cancer and polyps. Polyps found before they become cancer can be removed, so these tests may prevent colorectal cancer. This is why these tests are preferred if they are available and you are willing to have them.
Once you have been diagnosed with colorectal cancer, your doctor will order tests to determine the extent (stage) of your cancer. Staging helps determine what treatments are most appropriate for you.
Staging tests may include imaging procedures such as abdominal and chest CT scans. In many cases, the stage of your cancer may not be determined until after colorectal cancer surgery.
The stages of colorectal cancer are:
- Stage I. The cancer has grown through the superficial lining (mucosa) of the colon or rectum but has not spread beyond the colon wall or rectum.
- Stage II. The cancer has grown into or through the wall of the colon or rectum but has not spread to nearby lymph nodes.
- Stage III. Your cancer has invaded nearby lymph nodes but is not affecting other parts of your body yet.
- Stage IV. Your cancer has spread to distant sites, such as your liver or lung.
Living With Rectal Cancer
If you have or have had colorectal cancer, you can take steps to manage the stress that accompanies the diagnosis.
- Learn about colorectal cancer so you can make informed decisions about your care.
- Have a schedule of follow-up tests and go to each appointment.
- Take care of yourself so that you are ready to fight cancer. This includes eating a healthy that includes plenty of fruits, vegetables and whole grains, exercising for at least 30 minutes most days of the week, and getting enough sleep so that you wake feeling rested.
- Accept help and support from family and friends.
- Talk with other cancer survivors or attend support groups.
Rectal Cancer Treatments
The type of treatment your doctor recommends will depend largely on the stage of your cancer. The three primary treatment options for colorectal cancer are surgery, chemotherapy, and radiation.
Surgery for colorectal cancer. If your cancer is small, localized in a polyp, and in a very early stage, your doctor may be able to remove it completely during a colonoscopy. Larger polyps may be removed using endoscopic mucosal resection. If the pathologist determines that it is likely that the cancer was completely removed, there may be no need for additional treatment.
Polyps that cannot be removed during colonoscopy may be removed using laparoscopic surgery. In this procedure, your surgeon performs the operation through several small incisions in your abdominal wall, inserting instruments with attached cameras that display your colon on a video monitor. The surgeon may also take samples from lymph nodes in the area where the cancer is located.
If your cancer has grown into or through your colon, your surgeon may recommend a partial colectomy to remove the part of your colon that contains the cancer, along with a margin of normal tissue on either side of the cancer. Nearby lymph nodes are usually also removed and tested for cancer.
If your cancer is very advanced or your overall health very poor, your surgeon may recommend an operation to relieve a blockage of your colon or other conditions in order to improve your symptoms. This surgery is not done to cure cancer, but instead to relieve signs and symptoms, such as bleeding and pain.
In specific cases where the cancer has spread only to the liver and if your overall health is otherwise good, your doctor may recommend surgery to remove the cancerous lesion from your liver. Chemotherapy may be used before or after this type of surgery. This treatment may improve your prognosis.
Chemotherapy. Chemotherapy uses drugs to destroy cancer cells. Chemotherapy for colorectal cancer is usually given after surgery if the cancer has spread to the lymph nodes. In this way, chemotherapy may help reduce the risk of cancer recurrence.
Chemotherapy can also be given to relieve symptoms of colorectal cancer that has spread to other areas of the body. Chemotherapy may be used before surgery to shrink the cancer before an operation. In people with rectal cancer, chemotherapy is typically used along with radiation therapy.
The following drugs are approved for use in colorectal cancer:
- bevacizumab (Avastin)
- capecitabine (Xeloda)
- cetuximab (Erbitux)
- fluorouracil (Adrucil, Efudex, Fluoroplex)
- irinotecan Hydrochloride (Camptosar)
- leucovorin Calcium (Wellcovorin)
- oxaliplatin (Eloxatin)
- panitumumab (Vectibix)
- ramucirumab (Cyramza)
- regorafenib (Stivarga)
- ziv-Aflibercept (Zaltrap)
Radiation therapy. Radiation therapy uses powerful energy sources, such as X-rays, to kill cancer cells that might remain after surgery, to shrink large tumors before an operation so that they can be removed more easily, or to relieve symptoms of colon cancer and rectal cancer.
Radiation therapy is rarely used in early-stage colorectal cancer. Radiation therapy, usually combined with chemotherapy, may be used after surgery to reduce the risk that the cancer may recur.
Targeted drug therapy. Drugs that target specific defects that allow cancer cells to grow are available to people with advanced colorectal cancer, including bevacizumab (Avastin), cetuximab (Erbitux), panitumumab (Vectibix) and regorafenib (Stivarga). Targeted drugs can be given along with chemotherapy or alone. Targeted drugs are typically reserved for people with advanced colorectal cancer.