Colon and Rectum Carinoma

Colon and Rectum Carcinoma

Colorectal cancer is the fourth most common cancer in the United States, affecting 140,000 people annually and causing more than 50,000 deaths. The colon is the last portion of the digestive system and the rectum is the end of the colon just above the anus. The colon extracts water and salts before the waste material is eliminated through the anus. Together, they form the large intestine. Cancers that begins in the colon and rectum are called colon cancer and rectal cancer. Together, they are known as colorectal cancer. In general, cancer than begins in any of the two regions can be called colorectal cancer. The inner wall of the large intestine is the primary site of these tumors. If benign, they are termed polyps. The malignant tumors can spread to other nearby organs. Cancer in colon and rectum include adenocarcinomas (more than 95%), sarcomas, carcinoid tumors (see article on neuroendocrine carcinomas, gastrointestinal stromal tumors,  and lymphomas.

 

Types of Colon and rectum adenocarinoma

Most colon cancers are adenocarcinomas, cancers that begin in cells that make and release mucus and other fluids. Adenocarcinomas account for about 90-95 percent of all colorectal cancers. The presence of mucus makes them very aggressive and therefore difficult to treat. It comprises of about 10-15 percent of adenocarcinomas.

Epidemiology

The frequency of colorectal cancer varies widely worldwide among different populations. This form of cancer is the third most common cancer in males and females in the United States. The influence of this disease is more widespread in the Western world than in Asian and African countries. The incidence of colorectal cancer is increasing in people who are becoming accustomed to the western diet.

Risk factors or causes

It is difficult to pinpoint the cause of colorectal cancer. Nevertheless, certain factors may be associated with colon and rectal cancer. These are the following:

  • Age – The chances of developing this disease increases with age. Colorectal cancer is more likely to occur as people get older. It is rare in young people unless they have inherited specific genes/risk factors.
  • Polyps – Polyps are fleshy glandular structures that project from the inner lining of the colon or rectum. Polyps which can turn cancerous are called adenomas while those which remain non-cancerous are called hyperplastic or inflammatory polyps. Polyps are usually found in people 50 years of age or older. Polyps can be safely removed by a process called polypectomy. Polyps and colon cancer tend to run in families. Familial adenomatous polyposis (FAP) is a rare, inherited disorder characterized by the presence of multiple polyps (hundreds to thousands) in the colon and rectum. Essentially all people with this syndrome will have colon cancer by age 40 if the colon is not removed. Colectomy (removal of the colon) is recommended in such cases. Celecoxib (an anti-inflammatory drug) has been approved by the FDA to treat FAP but is not without risks.
  • Previous history – Risk increases with previous incidence of colon cancer, breast cancer (in women), ovarian cancer and uterine cancer.
  • Family history – If a close family member had this cancer, the chances for developing this disease increases in other members of the family. Hereditary Non-Polyposis Colon Cancer (HNPCC) is a genetic disorder increases the risk of colon cancer.
  • Ulcerative colitis or Crohn colitis – These two forms of inflammatory bowel disease increase the chances to develop colorectal cancer.
  • Diet – High amount of red and processed meats in diet and less vegetables and fruits can increase the risk.
  • Obesity, type 2 diabetes and alcohol abuse – These can all increase the risk of colorectal cancer.
  • Exercise – An inactive lifestyle may be associated to development of colorectal cancer
  • Smoking – Cigarette smoking can be a cause of colorectal cancer.

Symptoms

Many cases of colon cancer have no symptoms. The following symptoms may indicate colorectal carcinoma.

  • Pain in the abdomen
  • Blood in the feces
  • Diarrhea or constipation
  • Stools becoming thin in caliber
  • Unexpected weight loss

Diagnosis

Diagnosis of colorectal cancer can be done with the help of the following screening tests in people age 50 or older with average risk:

  • Fecal occult blood test (FOBT) – This detects blood in the stool, either by use of a chemical called guiac (guiac FOBT) or by by immunochemistry (immunochemical FOBT). It should be performed yearly in people starting at age 50 if they do not have risk factors indicating screening should be started earlier. If blood is found, a colonoscopy must be performed.
  • Sigmoidoscopy – In this test, the rectum and sigmoid colon (last part of colon) can be visualized and studied with the help of a sigmoidoscope (a metal or plastic tube lighted at one end). Abnormal growths can be detected by this process, but only at the end of the colon. The colon needs to be cleaned, but sedation is not required and it can be done in the office. This is suggested to be done every 5 years in people over age 50.
  • Colonoscopy – Precancerous and cancerous growths throughout the colon can be detected by this technique. A colonoscope (an endoscope) is used in this case. Tissue can also be removed from the site and biopsied. Sedation is required and colon should be well cleaned before the test is done. This should be done every 10 years in people over 50 with no specific risk factors.
  • Virtual colonoscopy (also called computerized tomographic colonography) –Computed tomographic colonography (CTC), also known as virtual colonoscopy, uses virtual reality technology to provide doctors with a 3-D image that enables them to conduct an evaluation of the entire colon and rectum. It is not as painful as colonoscopy and therefore sedation is not required. The colon must still be cleaned out. It is recommended every 5 years.
  • Double contrast barium enema (DCBE) – DCBE can detect cancers and polyps to some extent (30-50 %). The patients receive an enema with barium sulphate. Air is also added. A series of x-rays then helps viewing the colon and rectum. This should be done every 5 years, and also involves cleaning out the colon.
  • Digital rectal exam (DRE) – It is a routine physical exam of the lower rectum performed to detect rectal tumors. In this test, the doctor inserts his gloved finger into the rectum to feel the presence of abnormal growths.

People at increased risk due to family history, genetic syndromes, or multiple risk factors may need to be screened more frequently.

Treatment

Treatment is mostly based on the stage and some other factors. They usually include the following:

Surgery

Surgical resection (colonoscopy) of the affected part can be done to remove Stage 0 colon cancer. More of the colon needs to be removed for stages I, II and III, thus making surgical resection more difficult. Stage II colon cancer patients may or may not receive chemotherapy or radiation after surgery. Stage III cancer is always treated with more than just surgery.

Chemotherapy

Chemotherapy using the drugs 5-fluorouracil, leukovorin, and oxaliplatin (FOLFOX) is commonly used. Capecitabine has also shown good results, and there are other choices of drugs. Chemotherapy is essential for stage III patients.

Survival in patients with stage IV colon cancer can be prolonged by chemotherapy. Monoclonal antibodies like Cetuximab (IMC-C225), Bevacizumab (Avastin), or Panitumumab (Vectibix), and others may be used for the treatment of colorectal cancer together with chemotherapy using FOLFOX or other regimens.

Radiation

Radiation therapy can be used to reduce the chances of recurrence of the disease. It can be used to shrink tumors before surgery, or if surgery is not possible. It can be used with chemotherapy.

Prognosis

Colon cancer can be effectively treated, if diagnosed early. The 5-year survival rate is high for patients of Stage I (74%), II (67% for early stage II) and III (73% for some III stages). In most cases, it is not possible to cure a stage IV cancer patient with colorectal cancer. Improvement in treatment is required for advanced stages.

There are several prognostic molecular markers for colorectal carcinoma, but more studies are required to establish their importance in prognosis of this disease.

References

  1. Greco P, Magro G. (2010) Pathologic examination and staging of rectal carcinoma: a critical review. Pathologica.;102(1):12-27.
  2. Jass JR. (2000) Histopathology of early colorectal cancer. World J Surg. Sep;24(9):1016-21.
  3. Kudo S, Kashida H, Nakajima T, Tamura S, Nakajo K. (1997) Endoscopic diagnosis and treatment of early colorectal cancer. World J Surg.;21(7):694-701.
  4. Carolyn C Compton (2003) Colorectal Carcinoma: Diagnostic, Prognostic, and Molecular Features. Mod Pathol 2003;16(4):376–388
  5. Zlobec I, Lugli A. (2008) Prognostic and predictive factors in colorectal cancer. J Clin Pathol. ;61(5):561-9.
  6. This article was originally published on September 3, 2012 and last revision and update was 9/4/2015.