Rectal Cancer

Along with colon cancer, rectal cancer is also known as colorectal cancer, because both start in the large intestine. Rectal cancer involves the last six inches of the large intestine. This is the rectum, where your body stores stool until a bowel movement. Rectal cancer usually starts with polyps on the inner lining of the rectum. Tumors in the lower rectum may also be close to the anal sphincter muscle, which is important for using the bathroom normally. This can affect treatment options. 

Types & Stages

Colorectal cancer arises from the lining of the colon or rectum, usually from cells that secrete mucus. Most colorectal cancers are adenocarcinomas. These cancers start in cells that make mucus to lubricate the inside of the colon and rectum. 

Other, much less common types of tumors can also start in the colon and rectum. These include:

• Carcinoid tumors. These start from special hormone-making cells in the intestine. 
   
• Gastrointestinal stromal tumors (GISTs) start from nerve cells in the wall of the gastrointestinal tract. Some are benign (not cancer). These tumors are most commonly found in the stomach and small intestine. They’re not commonly found in the colon or rectum.
   
• Lymphomas are cancers of immune system cells. They mostly start in lymph nodes, but they can also start in the colon, rectum or other organs.
   
• Sarcomas can start in blood vessels, muscle layers or other connective tissues in the wall of the colon and rectum. Sarcomas of the colon or rectum are rare. 

Signs & Symptoms

Rectal cancer may not cause symptoms early on. Symptoms usually happen when the disease is advanced. Signs and symptoms include:

• a change in bowel habits, such as diarrhea, constipation or a more-frequent need to pass stool
• a feeling that the bowel doesn't empty completely
• abdominal pain
• dark maroon or bright red blood in stool
• narrow stool
• unexplained weight loss
• weakness or fatigue

Anyone experiencing these symptoms should speak with their primary care physician.

Diagnosis

Rectal cancer diagnosis often begins with an imaging test to look at the rectum. It can also be found during a screening test for colorectal cancer. Colonoscopy is considered the gold standard because it is the only test that can identify and treat polyps in the entire colon. If a polyp is detected during screening, it often can be removed and biopsied at that time, eliminating the need for additional procedures. This is called a polypectomy. 

While people often dread undergoing a colonoscopy, recent changes make it a gentler experience. For example, Stony Brook uses many different kinds of bowel preparations—some are even in pill form. Your doctor will determine which preparation you’ll tolerate best. 

Treatment

Treatment for rectal cancer may begin with surgery to remove the cancer. If the cancer grows larger or spreads to other parts of the body, treatment might start with medicine and radiation instead. Surgery to remove the cancer can be used alone or in combination with other treatments. 

Procedures may include:

• Removing very small cancers from the inside of the rectum. Very small rectal cancers may be removed using a colonoscope or another specialized type of scope inserted through the anus. This procedure is called transanal endoscopic microsurgery, a less invasive procedure than the traditional approach for reaching lesions high up in the rectum to cut away the cancer and some of the healthy tissue around it.

• Removing all or part of the rectum. Larger rectal cancers that are far enough away from the anus might be removed in a procedure that removes all or part of the rectum. This procedure is called low anterior resection. Nearby tissue and lymph nodes are also removed. This procedure preserves the anus so that waste can leave the body as it usually would.

  How the procedure is performed depends on the location of the cancer. If it affects the upper portion of the rectum, that part of the rectum is removed. The colon is then attached to the remaining rectum. This is called colorectal anastomosis. All of the rectum may be removed if the cancer is in the lower portion of the rectum. Then the colon is shaped into a pouch and attached to the anus, called coloanal anastomosis.

• Removing the rectum and anus. For rectal cancers that are located near the anus, it might not be possible to remove the cancer completely without hurting the muscles that control bowel movements. In these situations, surgeons may recommend an operation called abdominoperineal resection, also known as APR. With APR, the rectum, anus and some of the colon are removed, as well as nearby tissue and lymph nodes. Your surgeon creates an opening in your abdomen and attaches the remaining colon. This is called a colostomy. Waste leaves the body through the opening and collects in a bag that attaches to the abdomen.
   
• Stony Brook uses the da Vinci® robotic surgical system for rectal cancer surgeries.

Causes & 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:

• 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.
   
• Race/Ethnicity. In the United States, Black people have a greater risk of colorectal cancer than do other races.
   
• Diabetes. People with type 2 diabetes may have an increased risk of colorectal cancer.
   
• Drinking alcohol. Heavy drinking increases the risk of colorectal cancer.
   
• A diet low in fiber. Colorectal cancer may be related to a diet low in vegetables and high in red meat.
   
• 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.
   
• 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 colorectal cancer risk. These may include familial adenomatous polyposis, also known as FAP, and Lynch syndrome. Genetic testing can detect these and other, rarer inherited colorectal cancer syndromes.
   
• Obesity. People who are obese have an increased risk of colorectal cancer compared with people considered to be at a healthy weight.
   
• Older age. Colorectal cancer can be diagnosed at any age, but most people with this type of cancer are older than 50. The rates of colorectal cancer in people younger than 50 have been increasing, but healthcare professionals aren't sure why.
   
• Radiation therapy for previous cancer. Radiation therapy directed at the abdomen to treat previous cancers may increase the risk of colorectal cancer.
   
• Smoking. People who smoke may have an increased risk of colorectal cancer.
   
• Too little exercise. If you're inactive, you're more likely to develop colorectal cancer.

Screening

Colorectal cancer screening reduces the risk of cancer by finding precancerous polyps in the colon and rectum that could turn into cancer. The American Cancer Society recommends that people undergo screenings starting at age 45 for more adults. Individuals at high risk should start screenings earlier and have more frequent follow-ups. 

Stony Brook offers additional screening methods, including:

• flexible sigmoidoscopy, in which the doctor looks inside your large intestine with a long, flexible tube with a camera attached (an endoscope). It goes through your anus and rectum.
   
• barium enemas 
   
• fecal occult blood testing
   
• CT colonography, also known as virtual colonoscopy. This latter method, while less invasive because it uses a CT scan to look at the lining of the colon, still requires bowel preparation. It’s generally used with patients who may have an existing colon blockage or if a colonoscopy carries risks, for example, from anesthesia. Unlike a colonoscopy, in which a polyp can be removed during the screening procedure, during a virtual colonoscopy, if a polyp is detected, you’ll need an additional procedure to treat and biopsy it.