Digestion, Men's Health, Women's Health | October 12, 2014 | Author: The Super Pharmacist
Colorectal cancer is the fourth most common of all cancer types. It is a form of cancer known as an adenoma, that tends to arise from polyps (benign growths in this region of the gastrointestinal tract). Early detection of these polyps, before the proliferation of cancerous cells is established, may significantly affect the mortality rate of this disease.
There are a number of factors and medical conditions associated with the increased risk of polyp development, which include:
In addition, the incidence of colorectal cancer has been found to have a component of genetic predisposition.This includes the association of genetic changes resulting in an over-expression of a protein called the epidermal growth factor receptor (EGFR). This is associated with malignancy and metastasis in colorectal cancer. Patients may have mutations in another group of genes called RAS.
Mutations in another gene called APC is associated with polyp formation and malignant cell growth, i.e. the very early stages of this type of cancer.
Early detection of cancer (or polyps) may be achieved by analysis of patient faeces (which contains colonic and rectal cells); specifically by detection of APC mutations. Colorectal cancer is also detected by more invasive methods such as colonoscopy or flexible sigmoidoscopy. Of these, sigmoidoscopy is associated with earlier detection.
A new option, colonoscopy in combination with faecal APC analysis, is associated with even more accurate diagnosis. However, colonoscopy is associated with disadvantages such as a perforation and mortality.
There are also new developments in the diagnostic and screening procedures for colorectal cancer.
These include a variation on endoscopy, which involves a capsule that can be swallowed and then transmits video telemetry from the relevant region of the gut. This may be an alternative to the more invasive (and thus potentially discomfiting) conventional methods of endoscopy used to diagnose cancer. However, the procedure carries risks, mainly that of capsule retention, in which cases minor surgery may be required to remove it.
Another alternative imaging technique is computed tomography (CT)-aided colonoscopy, or virtual colonoscopy. This is the combination of CT imaging with virtual reality software, to give a three-dimensional image of the colon or rectum. This may address the drawbacks of conventional colonoscopy, which include a degree of invasiveness, concomitant patient discomfort, and the necessity of intravenous sedation. The efficacy of virtual colonoscopy may be affected by variables such as the presence of stool and/or fluid in the region of the tract to be visualised. However, research indicates that the procedure is as effective as conventional techniques. Some studies indicate the positive impact of virtual colonoscopy in screening for disorders such as colorectal cancer.
Early-stage colorectal cancer is defined as stage 0-2.
Surgery may be the most effective treatment for early stage colon and rectal cancer. If polyps are detected, they may be excised in order to prevent the progression to malignant growths and metastases. This is associated with a high probability of avoiding the development of malignancy.
Tumours can also be excised; alternatively, the regions of the lower gastrointestinal tract containing multiple tumours can be removed, and the remaining 'ends' sutured together, which is known as resection. There are cases in which the tumours are too numerous, or have spread too extensively, for resection to be performed effectively or safely. Therefore, other treatments that reduce tumour size and/or inhibit their growth are necessary beforehand.
The more effective of these are described below.
There are many therapy options for colorectal cancer that combine antibodies, or molecules that detect and bind to specific proteins in the body, with chemotherapeutic agents. The antibodies inhibit EGFR-associated proliferation, while the chemotherapy kills cancer cells. Unfortunately, cancers with mutations in RAS genes appear to be resistant to this option.
Recent research indicates that significant increases in GAB2, a protein acting downstream of EGFR, is associated with progression in colorectal cancer. This may represent a novel therapeutic target. Other potential targets include VEGF, a growth factor that plays an important role in blood vessel developments. As tumours often 'grow' their own micro-vessels to survive, VEGF inhibition may be a viable strategy to combat tumour growth and metastasis.
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