What is colorectal cancer?

Risk factors: Increasing age, a family history of colorectal cancer, familial polyposis, ulcerative colitis, and Crohn disease increase risk. A high-fat, low-fiber diet and inactivity can play a role, but the mechanism of this association is not known.

Etiology and the disease process: Some changes take place in the colon before cancer develops. A small area of precancerous cells will begin to form on the surface of the intestine. These cells can mutate into cancerous cells and will continue to grow in both directions outward from the surface and inward though deeper layers of tissue that form the multiple layers of the intestinal wall. As the abnormal growth invades these layers, it can encroach on blood vessels and lymph nodes, from which cancer cells can travel to the liver or other organs. Liver metastases are common with advanced disease.

The most common large intestine abnormality is noncancerous growths called polyps. Polyps grow into the intestine from its walls. Some polyps have a stalk. Polyps usually grow in the sigmoid colon and the rectum. Adenomatous polyps (derived from glandular tissue) are more likely to become malignant (cancerous). Approximately 25 percent of people with colon cancer have polyps somewhere else in the large intestine.

Familial polyposis is a hereditary condition. There is a genetic predisposition to grow many, even one hundred or more precancerous adenomatous polyps in the large intestine. Cases of colorectal cancer due to this condition appear before the age of forty, unlike colorectal cancers due to other causes, which have a higher rate of incidence with advancing age. Polyps are removed unless there are so many of them that it is better to remove a section of the large intestine containing the polyps. Frequent examination of the large intestine is necessary to watch for new growth. The most extreme measure to prevent the growth of more polyps is the surgical removal of the rectum and anus. A surgical opening is made in the abdominal wall (ileostomy), where solid waste can be collected in a pouch.

Incidence: In 2014 the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) Program estimated that colorectal cancer is the fourth most common cancer for men and women in the United States. It is also estimated to be the fourth leading cause of death. SEER estimated that in the United States there would be 96,830 new cases of colon cancer and 40,000 new cases of rectal cancer (136,830 cases combined) in 2014, representing 8.2 percent of all new cancer cases. NCI SEER also estimated that there would be 50,310 colorectal cancer deaths in 2014, representing 8.6 percent of all cancer deaths. From 2000 to 2004, the median age at diagnosis for colorectal cancer was seventy-one years. The median age at death was seventy-five years. From 2007 to 2011, the median age at diagnosis for colorectal cancer decreased to sixty-eight years for people of both sexes and all races in the United States, according to SEER in 2014

SEER also reported in 2014 that men, in general, had higher incidence rates per 100,000 people than women from 2007 to 2011. Among men in the United States, African Americans have the highest rate at 62.3 per 100,000; white Americans, 49.6; Asian/Pacific Islanders, 43.1; Hispanics, 44.3; and American Indian/Alaska natives, 45.5. Among women, African Americans have the highest incidence rates at 47.5 per 100,000, followed by white Americans, 37.3; American Indian/Alaska natives, 35.5; Asian/Pacific Islanders, 32.0; and Hispanics, 30.6. Trends in colorectal cancer incidence for US men and women from 1975 to 2004 showed a decline for all races and ethnicities. In 2014, SEER reported that rates for new colorectal cancer cases in the United States fell an average of 3.1 percent each year between 2002 and 2011, while death rates fell an average of 2.9 percent annually during the same period.

Symptoms: There are no symptoms of early colorectal cancer. Screening is the most important component in prevention and early detection. Symptoms such as weight loss, constipation, blood in the stool, and liver disease indicate a more advanced stage of disease.

Screening and diagnosis: There are several tests for screening and diagnosis. The type and frequency of testing depend on the patient’s age and medical history. A yearly fecal occult blood test/fecal immunochemical test (FOBT/FIT) is recommended in people age fifty or older. A physician decides which additional test—double-contrast barium x-ray, flexible sigmoidoscopy, or colonoscopy—should be given to each person, starting at age fifty and every five to ten years after for those without new symptoms.

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  Fecal occult blood test (FOBT): Three fecal samples taken at different times are placed on special cards that are sent to the laboratory for testing. The presence of blood in the sample indicates that further testing is required. A positive FOBT does not necessarily mean cancer. Blood can come from hemorrhoids, a noncancerous polyp, or inflammatory bowel diseases such as Crohn disease or ulcerative colitis.





• Fecal immunochemical test (FIT): Also known as an immunochemical fecal occult blood test (iFOBT), to detect blood in the feces. The advantage to this test is that the patient is not required to restrict certain foods and medications before collecting the sample. Also, early evidence indicates that the FIT might be more specific in detecting blood than the FOBT.





• Double-contrast barium x-ray: An x-ray of the colon and rectum using barium for contrast. Growths, narrowing of the colon, and evidence of inflammation can be seen, as the barium outlines the large intestine. Biopsies and polyp removal are not possible with this procedure.





• Flexible sigmoidoscopy: The sigmoidoscope is a flexible tube with a light and a tiny camera at the tip. The instrument is introduced into the rectum. Polyps, other growths, and evidence of inflammation can be seen in the lower one-third of the intestine and rectum. Biopsies (tiny samples of abnormal tissue) can be taken of tissue that appears abnormal.





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  Colonoscopy: The colonoscope is a flexible tube with a light and tiny camera at the tip. The patient is given conscious sedation and frequently sleeps though the procedure. The tube is introduced through the rectum and is passed into all three sections of the large intestine. Biopsies of abnormalities can be taken. The colonoscopy is the only test that visualizes the entire colon and allows for biopsy of abnormalities.

If a biopsy is positive for cancer, further testing is required to see if the cancer has spread. The process is called staging.

• Stage 0: Very early cancer is present on the innermost layer of the intestine.





• Stage I: Cancer is in the inner layers of the colon.





• Stage II: Cancer has spread through the muscle wall of the colon.





• Stage III: Cancer has spread to the lymph nodes.





• Stage IV: Cancer has spread to other organs.

Treatment and therapy: Treatment options vary according to disease stage and the age and general health of the patient. The main treatment categories are surgery, chemotherapy, radiation therapy, and targeted therapy (specifically targeting cancer cells by stimulating the immune system). More than one of these treatments may be used. Many patients choose to get a second opinion, which allows them to have increased confidence in the treatment option that they have chosen with their physician or to explore other options. It is very important that colorectal cancer patients ask questions necessary to feel confident that they understand the disease and treatment. Patients are advised to take a trusted friend or family member to appointments and write down questions at home to ask their physician.

Surgery is the primary treatment. The type of surgery depends on the stage of disease. Laparoscopic surgery, which involves a small incision in the abdomen, can remove some Stage 0 and Stage 1 tumors and cancerous polyps (polypectomy). Surgery in the early stages can be curative. Surgical procedures range from polypectomy, often performed during a colonoscopy, to resection (removal) of major sections of the large intestine or rectum. When resection is performed, up to one-third of the intestine is removed. The ends of each section are then attached (anastomosis) where there is healthy tissue on each side. Cancer of the rectum and anus may require colectomy, a process in which the surgeon removes part or all of the colon, brings a normal section of the large intestine through an opening in the abdomen, and attaches a bag to collect solid waste.

External beam radiation therapy focuses high-energy beams directly into the tumor from outside the body, killing the cancer cells. Radiation usually follows surgery to remove a large mass or tumor. Radiation therapy is very precise and can be focused on small areas of tumor cells not seen during surgery. There are times when radiation is used before surgery to shrink a tumor and ease removal.

Radiation for colon cancer is performed with a linear accelerator. Precision calculations determine the most direct path to the tumor cells while damaging the fewest normal cells. Treatment lasts only a few minutes per day and might continue for several weeks.

Endocavitary radiation treatment for cancer of the rectum and anus is performed internally. A small, handheld device is introduced into the rectum, where the dose of radiation can more directly reach the cancer cells.

Side effects from radiation include skin irritation, nausea, bladder irritation, bowel incontinence, diarrhea, rectal irritation, and fatigue. Sexual dysfunction can occur in men and women.

Chemotherapy involves several strategies. It can be used after surgery when all evidence of cancer is gone, or it can work to prevent a return of the cancer, which is called adjuvant chemotherapy. Drugs used to treat colorectal cancer include fluorouracil (5-FU), capecitabine (Xeloda), oxaliplatin (Eloxatin), and irinotecan (Camptosar).

Systemic chemotherapy is the introduction into the body of toxic, cancer-fighting chemicals, which find cancer cells and kill them. Cancer cells divide more rapidly than normal cells. Chemotherapy drugs get inside the cancer cells more rapidly and kill them. A targeted variation is injecting chemotherapy drugs directly into an artery supplying blood to an organ (liver) that contains tumor cells.

Side effects of chemotherapy are due to the toxicity of the drugs, which kill cancerous and noncancerous cells. Common side effects are severe diarrhea, low blood counts, nausea, and vomiting. Medications are available to control the nausea and vomiting.

Targeted therapy exploits unique abnormalities of cancer cells other than just rapid cell division. Proteins called monoclonal antibodies selectively find the cancer cells and kill them. There are fewer side effects, possibly from less damage to normal cells. Targeted therapy is not without side effects or danger. Lung scarring, rashes, fatigue, infection, and allergic reactions are all realities with this therapy. Monoclonal antibody and target therapy drugs include bevacizumab (Avastin), cetuximab (Erbitux), and panitumumab (Vectibix).

Prognosis, prevention, and outcomes: People who are aware of their family history for colorectal cancer or polyps are in a good position to lessen their chances for contracting colorectal cancer. High-fat, low-fiber diets are implicated in higher rates of CRC, but the mechanism is not known. People who eat lean meat, smaller portions of meat, and more vegetables and grains have lower rates of CRC. Physical activity also seems to be important.

It is imperative that beginning at age fifty, yearly FOBT/FIT testing is performed and that colonoscopy, flexible sigmoidoscopy, or double-contrast barium x-ray is also performed every five to ten years. The main reasons people do not have these screening tests are concerns about the colon-cleansing procedure before testing, unease about taking fecal samples for the FOBT, and embarrassment.

Excellent prognosis or cure is associated with early detection. Stages 0, I, II, and III are potentially curable. Colorectal cancer that has not spread (metastasized) or invaded the intestinal wall has a greater chance for cure. More than 90 percent of patients receiving treatment during the early stages will survive at least five years. Some 39 percent of colorectal cancer is found in the early stages.

Stage IV cancer has spread to organs such as the liver, ovaries, lungs, or peritoneum. Surgery is performed not to cure the cancer but to prevent the colon from becoming blocked by the tumor. Liver metastases have been successfully removed through surgery. There have been some cures from this procedure, but this stage of disease is difficult to cure. Multiple therapies are used with Stage IV disease and include targeted therapies, chemotherapy, freezing tumors, and radiation.

Amer. Cancer Soc. Colorectal Cancer. N.p.: ACS, 2013. Digital file.

Brown, Gina. Colorectal Cancer. New York: Cambridge UP, 2007. Print.

Cassidy, Jim, Patrick Johnston, and Eric van Cutsem, eds. Colorectal Cancer. New York: Informa Healthcare, 2007. Print.

Centers for Disease Control and Prevention. "Colorectal (Colon) Cancer." CDC.gov. CDC, 28 July 2014. Web. 17 Sept. 2014.

Hamilton, Stanley R., et al. Cancers of the Colon and Rectum: A Multidisciplinary Approach to Diagnosis and Management. New York, Demos, 2013. Digital file.

Holen, Kyle, and Ki Young Chung. Dx/Rx: Colorectal Cancer. Sudbury: Jones, 2008. Print.

Jenkins, Julianne E. Colorectal Cancer: Risk, Diagnosis, and Treatments. New York: Nova, 2011. Digital file.

LaRusso, Laurie. "Colon Cancer." Health Library. EBSCO, 12 Sept. 2014. Web. 17 Sept. 2014.

LaRusso, Laurie, and Pamela Jones. "Rectal Cancer." Health Library. EBSCO, 27 May 2014. Web. 17 Sept. 2014.

MedlinePlus. "Colorectal Cancer." MedlinePlus. US NLM/NIH, 2 Sept. 2014. Web. 17 Sept. 2014.

Natl. Cancer Inst. "SEER Stat Fact Sheets: Colon and Rectum Cancer." SEER.cancer.gov. NCI/NIH, 2014. Web. 17 Sept. 2014.

Natl. Inst. of Health. "Colorectal Cancer." Report.NIH.gov. NIH, 29 Mar. 2013. Web. 17 Sept. 2014.