The first few feet of large intestine are referred to as the colon. The last 8-12 inches of large intestine are called the rectum. Colon and rectal cancer (also known as colorectal cancer) occurs when a mass grows within the inner lining of the large intestine. This often starts as a benign polyp that over time continues to grow and eventually transforms into an invasive tumor. The location of the tumor is what determines whether it is called a colon cancer or a rectal cancer.
Colon and rectal cancers combine to be one of the most common malignancies in the United States, with more than 130,000 Americans diagnosed each year. About 5% of Americans will be diagnosed with colorectal cancer in their lifetime.
Age is the most significant risk factor for colon cancer. Most colon cancer occurs in people over the age of 50 and the risk increases with age. Family history also is an important risk factor. Approximately 20% of colorectal cancers are hereditary. In particular, first degree relatives, such as siblings or parents, who have been diagnosed with colorectal cancer could be a significant risk factor. Other risk factors include a history of colorectal polyps as well as long standing inflammatory bowel disease such as Crohn’s colitis or ulcerative colitis.
Early in its course, colon cancer can be asymptomatic. As the tumor grows, symptoms will start to develop. Early symptoms are often related to bleeding. These can be as obvious as blood in your stool or on tissue paper after having a bowel movement. Subtle symptoms such as fatigue, however, can be a sign of slow indolent bleeding that is not visible to the eye, but results in low blood levels in your body over time. This is called anemia. Late symptoms include abdominal pain, abdominal distention, and/or nausea or vomiting as a result of an obstructing tumor. Unexpected weight loss also can be seen in advanced disease.
Most colon and rectal cancers are found during a colonoscopy. Screening colonoscopies are recommended starting at age 50 in patients without a significant family history of colon or rectal cancer. A significant family history may be an indication to perform screening colonoscopy before age 50. If you have symptoms that are suspicious for colon or rectal cancer, the colonoscopy is referred to as diagnostic. Any concerning polyps or masses visualized during your colonoscopy will be biopsied and evaluated for cancer by our pathologists.
Most colon cancers are found fairly early, and treatment usually starts with surgery to remove about a 12-18 inch long segment of large intestine that contains the cancer. It is also important to remove the lymph nodes surrounding the tumor. Occasionally, surgery alone is not enough to treat that cancer and chemotherapy is added to reduce the chance of cancer recurrence.
The decision to treat with chemotherapy is often based on the final pathologic evaluation of the cancer after it has been removed by surgery. Indications for chemotherapy are usually related to the presence or absence of cancer in the lymph nodes although other indications do exist.
The rectum is surrounded by fatty connective tissue and as a result, the ability to remove some rectal cancers is improved by first treating the cancer with combined chemotherapy and radiation. The goal of the chemoradiation is to shrink the tumor prior to surgery. The decision to treat with chemoradiation prior to surgery will be made by your team of physicians.
Most colon or rectal cancer surgery can be performed in a minimally invasive fashion through the use of multiple small incisions rather than one larger incision. This allows for shorter hospital stays and faster recovery with less pain and less complications. The type of surgery depends on the location of the tumor and specific details will be provided by your surgeon.