Thursday, 29 March 2018

Colon Cancer: Polyps, The Main Precursors

Colon cancer: Polyps, the main precursors.

Colon Cancer: Polyps, The Main Precursors
Colon Cancer: Polyps, The Main Precursors

Certain types of polyps that grow in the colon are the precursors of more than 95% of cancer cases in this organ. The risk appears at the 50-year border and could be avoided with the detection and removal of these premalignant lesions.

The colon cancer or colorectal cancer is precisely the most frequent tumor diagnosed in USA, with 41,441 cases in 2015. In both men and women, it is the second most frequent tumor after prostate and breast cancer.

Despite the frequency, it is a tumor whose survival has doubled in the last 20 years. In addition, retrospective analyzes have shown five-year survival rates after surgery of metastases of up to 70%, "a milestone and a breakthrough", considers this scientific society.

But still more than 15,000 people die every year in USA as a result of cancer of the large intestine and rectum, according to 2014 data from the sources, although the trend is decreasing.

A mortality that could fall even more if family history was taken into account, another of the risk factors, and we would undergo 50-year-old screening programs, such as stool occult blood and colonoscopy. , important for early detection.

But prevention also involves a balanced diet rich in fruits, vegetables and fiber and low-fat foods ; reduce tobacco and alcohol; maintain a normal body weight and exercise on a regular basis.

Why do polyps appear in the colon?

Polyps appear in the colon mucosa due to a combination of factors, such as lifestyle, especially feeding. But the origin lies in a failure in the mechanism of cell regeneration by not self-destruct at the end of life (apoptosis or programmed cell death), which causes an uncontrolled increase in cells. The same process that generates malignant tumors.

Polyps hardly show symptoms. Nor when they grow and turn into cancer. The warning light should come on if there are changes in bowel habit, abdominal pain and bleeding.

"We know that polyps take about ten years to degenerate into cancer. For that reason, if nothing was found in a colonoscopy, the intervals of 5 to 10 years to perform the controls set the parameters.

Types of polyps

But not all polyps end up degenerating into malignant tumors, only 5% of them. But it is true that that small percentage is the precursor of more than 95% of cancer cases in the large intestine. Everything depends on the type that is:

Inflammatory : There is no risk of cancer and the cause may be some ulcer.

Hyperplastic : They also do not degenerate into cancer.

Adenomas:  The most common and the most likely to become malignant. Several subtypes: tubular, villous and tubulo-villi.

Serrated: Less common but also at risk of becoming cancer.

According to the form of growth, they can be classified as:

Pediculate: it has a mushroom shape with stem, less risk of degenerating into cancer.

S├ęsil: It lacks stem but it does have a base of implantation, like a wart.

Flat and even depressed (inward): a high risk of being carcinogenic and is the most complicated to extract with endoscopy.

The size of the polyp also influences the risk of degenerating into cancer, a sessile or pedunculated type must be greater than one centimeter to lead to cancer, while a plane of a few millimeters can already be.

The polyps are detected and extracted with colonoscopy , an image and therapeutic test in which the endoscope covers the meter and a half of the large intestine that requires a previous intestinal cleansing and is usually performed with sedation.

Colon cancer and its risk factors

The most frequent colon cancer is, in 90% of cases, the adenocarcinoma that originates in the glands, while lymphomas, sarcomas and melanomas are more rare.

The main screening tests for precancerous polyps and tumors are the stool blood test and the colonoscopy.

"However, this screening in USA is in a situation of inequality, since the coverage of the program differs according to the Autonomous Communities. In some there is almost 100% coverage and others have little coverage or lack a screening program, "denounces the an American Association Against Cancer that calls for this test to be implemented throughout the national territory.

The main risk factor for colon cancer is age, in the 50s. "In studies it has been proven that from that age the appearance of polyps that could degenerate into cancer begins to increase and that is due to that cellular failures are accumulating.

Family history is another of the risk factors both for tumors generated by polyps (more than 95%), and for those non-polyposis hereditary syndromes (less than 5%) that are due to certain genetic mutations that pass from parents to children, like Lynch syndrome .

Advances in the treatment of colon cancer

The treatment of colon cancer, as has occurred in other tumors, has been a great advance in the last twenty years. It is a tumor that responds positively to surgery along with chemotherapy and is also receptive to biological therapies, in combination with chemotherapy, which allow preselecting patients based on genetic mutations.

These target treatments consist of antiangiogenic monoclonal antibodies (which inhibit the formation of the vessels that the tumor needs to grow) and others directed to genetic alterations, such as EGFR.

The immunotherapy or immune stimulation to fight the tumor, a therapeutic strategy that is already a reality in melanoma or lung, has not yet been proven effective in colorectal cancer system.

It seems that, for the moment, this tumor is not so sensitive, except in a subgroup of patients with microsatellite instability (less than 5% of all cases) and who are chemoresistant. They have a worse prognosis but they seem to be showing more sensitivity to immunotherapy.

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Colon Cancer: Polyps, The Main Precursors
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