Colorectal Cancer

What is colorectal cancer?

Colorectal cancer is an abnormal proliferation of cells in the colon or rectum or in the appendix. Colorectal cancer is the third leading cause of death from cancer among men and women all over the world wide but more common in developed countries. About 60 % of cases were diagnosed in the developed world. It is commonly known as colon cancer or bowel cancer. It is commonly manifested by rectal bleeding and anemia which are sometimes associated with weight loss and changes in bowel habits.

 

Most colorectal cancer occurs due to increasing age and lifestyle changes with only a minority of cases associated with underlying genetic disorders. It usually starts in the lining of the bowel then grows into the muscle layers underneath, and through the bowel wall. Screening is effective in preventing the complications. It is recommended after the age of 50 and continuing until a person is 75 years old. Most commonly diagnostic measure is sigmoidoscopy or colonoscopy.

Cancers in the first stage ,that are confined within the wall of the colon are often curable with surgery while cancer that has spread widely around the body is usually not curable and management then focuses on extending the person’s life via chemotherapy and improving quality of life.

                                       colo rectal cancer

 

  •  Etiology of colorectal cancer.

  • Risk factors of colorectal cancer.

  • Distribution of colorectal cancer.

  • Clinical presentation of colorectal cancer.

  • Pathology of colorectal cancer.

  • Physical examination of colorectal cancer.

  • Staging and prognosis of colorectal cancer.

  • Diagnostic measures of colorectal cancer

  • Therapy of colorectal cancer.

  • Follow-up of colorectal cancer.

  • Alternative therapies for colorectal cancer.

  • Prevention of  colorectal cancer.

  • Conclusion.

 

Etiology of colorectal cancer.

The exact etiology of colorectal cancer is not well known. It is believed that colorectal cancer occur when there is an alteration in the normal cells of colon. Normally there is a systematic and controlled division of healthy cells for the proper functioning of the body.In case of colorectal cancer there is an abnormal multiplication of cells in an uncontrolled manner. As a result of this abnormal cell growth in colon and rectum leads to the development of precancerous cell in the lining of the intestine.Over a period of time some this abnormal cells can change in to cancerous cells.Colorectal cancer can arise through two mutational pathways: chromosomal instability or microsatellite instability. Genetic mutations at germline are the basis of inherited colon cancer syndromes; an accumulation of somatic mutations in a cell is the basis of sporadic colon cancer.

Risk factors of colorectal cancer.

  • Hereditary polyposis syndromes.
  1. Familial polyposis (high risk).
  2. Gardner’s syndrome (high risk).
  3. Turcot’s syndrome (high risk).
  4. Peutz-Jeghers syndrome (low to moderate risk) .
  • Inflammatory bowel diseases (IBD), both ulcerative colitis and Crohn’s disease increases the risk for the development of colorectal cancer.
  • Family history of “cancer family syndrome.”
  • Heredofamilial breast cancer and colon cancer.
  •  Previous  history of colorectal carcinoma risk the risk of developing the disease again.
  • Women undergoing irradiation of gynaecologic cancer.
  • Risk of  colorectal cancer increases when the first degree relatives affected with it .
  • Age over 50 years:- Most  identified cases of colorectal cancer above the age of 50 years . Colorectal cancer  can occur in younger age group but prevalence is less.
  • Race:- The  colorectal cancer  more in African – American and American -Indians as compared to others.
  • Diet containing high fats and low fiber- one of the common risk factor associate with the development of the colorectal cancer is the diet containing  the low fiber and high calories and fats. Studies shown that increased risk of colorectal cancer is more in people consuming red meat more.
  • Lack of exercise or sedentary life style is found to be another important risk factor for the development of colorectal cancer.So improving the activity or doing regular exercise reduces the risk of colorectal cancer.
  • Diabetes: – It is found that colorectal cancer is more in client with diabetes and insulin resistance.
  • Obesity increases the risk of developing colorectal cancer. The risk of dying obese client with  colorectal cancer is   more compared to that of the clients with normal weight.
  • Smoking:- Nicotine also increases the risk of developing colorectal cancer.
  • Alcohol:-Chronic alcoholism or heavy consumption of alcohol increases the risk of colorectal cancer.
  • Radiation:-When radiation therapy is used as  treatment for  cancer  of  abdomen increases the risk of developing colorectal cancer.
  • If the client have the previous history of ovarian or endometrial  cancer then the risk for the development of colorectal cancer is more.
  • Hereditary nonpolyposis colorectal cancer: autosomal dominant disorder characterized by early age of onset (mean, 44 years),  synchronous and metachronous colon cancers, and right-sided or proximal colon cancers and mucinous and poorly differentiated colon cancers. Diagnosis can be made through genetic testing for germline mutations in hMSH2 or hMLH1.

 Distribution of colorectal cancer.

  1. Rectosigmoid and rectum (30—33%)
  2. Descending colon (40—42%)
  3. Transverse colon (10—13%)
  4. Cecum and ascending colon (25—30%)
  •  Fifty percent of rectal cancers are within reach of the examiner’s finger.
  •  Fifty percent of colon cancers are within reach of the flexible sigmoidoscope.

 Clinical presentation of colorectal cancer.

The general signs and symptoms of colorectal cancer are change in the bowel movement,some time it is presented as diarrhea or in the state of constipation.Bleeding from the rectum or malaena (blood in the stool )is the another classic symptom of colorectal cancer.Other general symptoms include feeling of incomplete evacuation of the bowel,persistent discomfort in the bowel such as pain,gas etc.  The client will be having malaise (generalized weakness ) and sudden or unexpected weight loss.

Presentation is initially vague and nonspecific It is useful to divide colon cancer symptoms into those commonly associated with the right colon and those commonly associated with the left colon, because the clinical presentation varies with the location of the carcinoma.

Right colon                    

  •  Anemia (iron deficiency resulting from chronic blood loss).
  •  Dull, vague, uncharacteristic abdominal pain may be present or patient may be completely asymptomatic.
  •  Rectal bleeding is often missed because blood is admixed with feces.
  •  Obstruction and constipation are unusual because of large lumen and more liquid stools.

Left colon

  • Change in bowel habits (constipation, tenesmus, pencil-thin stools, diarrhea).
  •  Rectal bleeding (bright red blood coating the surface of the stool).
  • Intestinal obstruction is frequent because of small lumen.

When to consult a doctor 

If you have any of the above symptoms like changes in the bowel habits or persistent changes in the consistency of the stool or blood in the stool immediately consult a doctor to identify the cause for it.Usually the  risk for the development of colorectal cancer increases after the age of 50years but in the case of any family history  disease proper screening should be done to identify the cases earlier.

Pathology of colorectal cancer.

Most tumours arise from malignant transformation of a benign adenomatous polyp. Over 65% occur in the rectosigmoid and a further 15% recur in the caecum or ascending colon. Synchronous tumours are present in 2-5% of patients. Macroscopically, the majority of cancers are either polypoidand ‘fungating’, or annular and constricting. Spreading of colorectal cancer occurs through the bowel wall. In case of rectal cancers invasion may exceed to the pelvic viscera and side walls. Most cases lymphatic invasion is common through both portal and systemic circulations to reach the liver and, less commonly, the lungs. Tumour stage at diagnosis is the most important determinant of prognosis.

Physical examination of colorectal cancer.

  • May be completely unremarkable.
  • Digital rectal examination (DRE) can detect approximately 50% of rectal cancers.
  • Palpable abdominal mass.
  •  Tenderness and  abdominal distention are suggestive of colonic obstruction.
  • Hepatomegaly is indicative of hepatic metastases.

Staging and prognosis of colorectal cancer.

  1. The expression of DCC protein (deleted in colon cancer) in tumor cells, evaluated immunohistochemically with antibodies against DCC, is a prognostic marker in patients with colorectal cancer stage II. In colorectal stage II carcinomas, the absence of DCC identifies a subgroup of patients with lesions that behave like stage III cancers.
  2. Table 7-10 describes staging classification and prognosis of colorectal cancer.
  • Table 7-10   – Staging Classifications and Prognosis for Colorectal Cancer

 

stage

 

Diagnostic measures for colorectal cancer.

Diagnosis of colorectal cancer is based on the signs and symptoms and some common investigation.It include the following.

  •  Blood test- it includes the complete   blood count and fecal occult blood test may be also done to identify the cause of bleeding.
  • Screening and diagnosis is best made with colonoscopy with biopsy.Colonoscopy examination helps to visualize the inner lining of the intestine by using a long ,slender and flexible tube with camera at the tip.It also helps to identify the ulcer,polyp, bleeding, tumors and areas of inflammation in lining of large intestine.The diagnosis of colorectal cancer is confirmed by taking biopsies from the suspected tumor or lesion with help of a surgical instrument passed through colonoscope.
  •  Virtual colonoscopy (VC) is a newer modality that uses helical (spiral) CT scan to generate a two- or three-dimensional virtual colorectal image. For Virtual colonoscopy (VC) there is no need of sedation, but like optical colonoscopy, it requires air insufflations and some bowel preparation (either bowel cathartics or ingestion of iodinated contrast medium with meals during the 48 hours before CT). It also involves exposure to radiation substantially. In case, if the client is identified  with lesions by VC will require traditional colonoscopy 30% of the time to biopsy the lesions.
  • X-ray with barium enema helps to get clear images of colon and to diagnose the colorectal cancer.

Therapy for colorectal cancer.

The treatment mainly depends on the stage of disease. The primary treatment available for the colorectal cancer is surgery,   radiation therapy and chemotherapy .

  • Early diagnosis and identification of clients helps to relieve the illness by early surgical removal of the curable disease (Dukes A, B) is necessary because survival time is directly related to the stage of the carcinoma at the time of diagnosis (see Table 7-10).
  • Surgery:-If the colorectal cancer is in early stage ,as a very small polyp it can be removed during the colonoscopy. When it is a large polyp it require laproscopic surgery for its removal.In case of invasive colon cancer partial colectomy is done to remove cancerous part along with the margin of normal tissue on the both side.In case of advanced colon cancer surgery is recommended not to cure the disease but to relieve the symptoms and discomfort.
  • Chemotherapy – chemotherapy drugs are used to destroy the cancerous cells.It is usually recommended when the cancerous cells have spread beyond the colon or through the lymph node.
  • Radiation:-In some cases combination of radiation and chemotherapy may be useful for rectal cancer. Radiation  therapy  in colon cancer is not routine due to the sensitivity of the bowels to radiation

Video of  Colorectal Cancer

  • Laboratory studies have identified molecular sites in tumor tissue that may serve as specific targets for treatment by using epidermal growth factor receptor antagonists and angiogenesis inhibitors. The monoclonal antibodies cetuximab [Erbitux] and bevacizumab [Avastatin] have been approved by the FDA for advanced colorectal cancer. Bevacizumab is an angiogenesis inhibitor that binds and inhibits the activity of human vascular endothelial growth factor (VEGF). Cetuximab is an EGFR (epidermal growth factor receptor) blocker that inhibits the growth and survival of tumor cells that overexpress EGFR. Cetuximab got synergism with irinotecan, and when it is given to in patients with advanced disease resistant, irinotecan increases response rate from 10% when cetuximab is used alone to 22% with combination of cetuximab and irinotecan. The addition of bevacizumab to fluorouracil/leucovorin in patients with advanced colorectal cancer has been reported to increase the response rate from 17% to 40%.In clients who undergone resection of liver metastases from colorectal cancer is treated with a combination of hepatic arterial infusion of floxuridine and IV fluorouracil which  improves the outcome at 2 years.
  • Palliative care:-In people with end stage colorectal cancer, usually palliative care is provided to improve quality of life. In case of non-curative colon cancer, surgical removal of some of the cancerous tissues can be done by  stent placement or bypassing part of the intestines. This is done to improve symptoms and reduce complications such as abdominal pain ,intestinal obstruction and bleeding from the tumor. Non-operative methods of symptomatic treatment include radiation therapy as well as analgesics to decrease tumor size and pain.

 Follow-up of colorectal cancer.

  1. Fecal occult blood testing every 6 months for a period of 4 years, then yearly.
  2. Colonoscopy yearly for initial 2 years, then every 3 years
  3. CEA level
  • CEA should not be used as a screening test for colorectal cancer because it can be elevated in patients with many other conditions      (smoking, IBD, alcoholic liver disease).
  • A normal CEA level does not exclude the diagnosis of colorectal cancer.
  • A baseline CEA level is useful in all patients with colorectal cancer because it can be used postoperatively as a measure of completeness of tumor resection or to monitor tumor recurrence; if used to monitor tumor recurrence, CEA should be obtained every 2 months for a period of 2 years, then every 4 months for a period of  2 years, and then yearly.
  • The role of CEA for monitoring patients with resected colon cancer has been questioned because of the small number of cancer cures attributed to CEA monitoring despite the substantial cost in dollars and the physical and emotional stress associated with monitoring.

Alternative therapies of colorectal cancer.

There is no defin

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