Colorectal cancer target referralcancer detection rate and diagnostic efficacy of the criteria - Essay Example

Etiology of colorectal carcinoma is not clear but a few etiological factors have been implicated. These are as under, 1. Geographic variations: The incidence of large bowel carcinoma shows wide variation throughout the world. It is much more common in North America, Northern Europe, then in South America, Africa, and Asia. Colorectal cancer is generally thought to be a disease of affluent societies because its incidence is directly correlated with the socioeconomic status of the countries. 2.

Dietary factors: Diet plays a significant part in the causation of colorectal cancer. A low intake of vegetable fiber-diet leading to low stool bulk is associated with higher risk of colorectal carcinoma. Consumption of large amounts of fatty foods by populations results in excessive cholesterol and their metabolites which may be carcinogenic. Excessive consumption of refined carbohydrates that remain in contact with colonic mucosa for prolonged duration changes the bacterial flora of the bowel, thus resulting in production of carcinogenic substances. 3. Adeno-carcinoma sequence: There is strong evidence to suggest that colonic adenoma-carcinoma arises from pre-existing adenomas referred to as adeno-carcinoma sequence.

Incidence of adenomas in population is directly proportional to the prevalence of colorectal cancer. 4. . cular genetics have revealed that there are sequential multi-step mutations in evolution of colorectal cancer from adenomas by mechanisms such as -catenin mechanism and microsatellite instability mechanism. Distribution of the primary colorectal cancer reveals that about 60% of the cases occur in the rectum, followed in descending order, by sigmoid and descending colon (25%), caecum and ileocaecal valve (10%), ascending colon, hepatic and splenic flexures (5%); and quite uncommonly in the tranverse colon.

Clinical symptoms in colorectal cancer appear after considerable time. These include occult bleeding, changes in bowel habits, loss of weight ( cachexia), loss of appetitie (anorexia), anemia, weakness, malaise. The most common complications are obstruction and hemorrhage; less often perforation and secondary infection may occur. The prognosis of colorectal cancer depends upon few variables such as extent of bowel movement, presence or absence of metastases, histological grade of tumor and location of the tumor.

The most important prognostic factor in CRC is however, the stage of the disease at the time of diagnosis. Three staging systems are in use. They include Duke's ABC staging, Astler - Coller Staging which is a further modification of Duke's Staging and TNM staging described by American Joint Committee (Mohan 601).The methods used in the diagnosis of CRC are as follows:Fecal Occult Blood Testing (FOBT)FOBT is one of the most effective methods for colorectal cancer screening. Reports reveala reduction in colorectal cancer mortality of 12%-33% in a long-term follow up available in four randomized controlled trials and three non-randomized trials of 330,000 and 200,000 individuals respectively.

FOBT isvery acceptable as it is non-invasive,programme.