Colon Cancer

3,566 views

Colon cancer develops from the lining of the “large bowel or colon. In 70% of cases, the tumor develops in the sigmoid (loop located in the left iliac fossa). Cancers of the colon and rectum are quite similar, are grouped under the term of colorectal cancers. There is always a malignancy liebekunien adenocarcinoma, developed from the mucosa.



Epidemiology

Cancer is the second in terms of frequency in women (after breast cancer) and third in men (after lung cancer and the prostate). Colon cancers have a high frequency in France every day, 100 people learn they have cancer colorectal. More precisely, we find 33,000 new cases per year, and 16,000 people die. Among non-smokers, they are the second leading cause of cancer mortality. Men are slightly more affected than women (incidence rate of 40 percent and 27-mile, respectively. In Africa and Asia, there are far fewer colorectal cancers than in Northern Europe or the U.S. (up to 20 times less). In addition, migrants who leave a poor country to a country where the risk is important, see their rates increase colorectal cancer within 10-20 years after their migration. These facts suggest that the Mode Life, food and physical effort, plays an important role on the risk of cancer. This suggests that effective prevention is possible (see below).
It is essentially a cancer in middle age, nearly 85% of cases occurring after age 65. Its frequency seems to increase.
Hereditary forms (Mendelian) are rare (less than 5% of cases) even if a family history is found in nearly one fifth of cases. The family forms are better prognosis.

Causes or risk factors

  • Age: rare for fifty years, colorectal cancers are becoming quite common about 65 years.
  • Heredity or mutations: the risk of colorectal cancer is higher if a relative has (had) a colorectal cancers.
    The risk is even stronger there are more people living in the family, that this case (s) are close (s) (father, mother, brother, sister), and that this case (s) are young .
    It has identified high-risk families, where people have a specific mutation that predisposes to cancer. These families represent only 5% of colorectal cancers:

    • Familial adenomatous polyposis (FAP in English) where numerous polyps appear in all carriers of mutated APC gene. In adulthood, one of these polyps inevitably degenerate into cancer unless the colon is removed by surgery. The APC gene is a tumor suppressor gene and its alteration is considered as an initiator of colorectal carcinogenesis (1% of colorectal cancers). It acts upstream of Wnt. Just a mutation in one of two copies of the gene for adenomatous polyposis induce family (with onset in adolescence of hundreds to thousands of polyps in the colon;
    • Lynch Syndrome, or Hereditary nonpolyposis colon (HNPCC in English). There are fewer polyps in FAP, and a lower risk of cancer, but surveillance is necessary by regular colonoscopies.
    • In addition to mutations that may be induced during learning (exposure to radioactivity or mutagenic products in food), a mutation in Notch can significantly accelerate or aggravate the colorectal carcinogenesis. This gene is a protein that acts as a “switch” that when he turned induces a cascade of reactions within the cell, allowing cell proliferation (normal and necessary as it is controlled in any cell, any organization, especially during embryonic development); The Notch gene, with the Wnt gene plays a major role in intestinal cell signaling, ensuring the development and organization of the intestine is an organ to be repeated continuously ( it is completely renewed in less than five days on a surface of villi and convolutions that if they were “extended flat” would be comparable to the size of a tennis court for doubles play. progenitor cells located in the hollow intestinal villi must constantly produce new cells, while being regulated …
      However, simultaneous activation (artificial or abnormal) of these two signaling pathways increases of more than twenty times the quantitative risk of developing adenomas (benign tumors) in mice intestinal, compared to single altered Wnt. The Notch gene seems particularly relevant in a synergistic phenomenon probably triggered by the activation of these two coupled channels, creating the conditions favoring the tumor .. Moreover, in mice, these tumors grow so fast and unusually important in the colon, suggesting the pathogenesis of colon cancer in humans.
  • Inflammatory bowel disease (IBD) including Crohn’s disease and ulcerative colitis: after twenty years, the risk of developing cancer is about one third if the entire colon is involved.
  • The lifestyle also plays an important role, as shown below in the section “Prevention”. Indeed, if we can not change our age or heredity, we can stop smoking, drink less alcohol, eat less meats but more vegetables and exercise more.

Diagnosis

  • Functional Signs.
    Colorectal cancer does not necessarily manifest signs. Therefore, after fifty years, we recommend screening tests.
    It can be shown by:

    • blood in the stool (fecal blood, apparent or hidden: in this case detected by a test);
    • continuing constipation of recent onset. Sometimes, complete obstruction, or persistent diarrhea. At the extreme, an occlusion may occur, or perforation of the tumor with peritonitis. The presence of gastrointestinal symptoms occurred in the months preceding the acute event guide to the origin of the cancer acute complications;
    • abdominal pain.

    The symptoms are often less specific, with, for example:

    • anemia which causes fatigue and a persistent skin more pale (due to intestinal bleeding). It typically occurs due to iron deficiency (low levels of serum iron and ferritin blood). The search for occult blood, in this case led to a diagnosis of colon cancer in about 10% of cases;
    • unexplained weight loss;
    • later, liver metastases can generate an abnormally enlarged liver on palpation.
  • Physical examination. It is, generally speaking, disappointing. The rectal examination, by a gloved finger inserted into the anus to look for possible anomalies rectum. Fast and inexpensive, this review only detect anomalies around the rectum (30% screening of rectal tumors).
  • Investigations.
    Colonoscopy (or colonoscopy) is the gold standard: a probe (long-coated flexible plastic) is inserted through the anus and then slid slowly into the intestine, most often during general anesthesia. It allows to observe the lining of the anus to the ileocolic junction, at the cecum and appendix, and to take samples. If you find a polyp, it is removed entirely and will be analyzed in the laboratory by histology, and its removal greatly reduces the risk of cancer (see below paragraph Prevention). Sigmoidoscopy, a more rapid and less complete, uses a short semi-rigid probe that allows exploration of the rectum and sigmoid colon, but not the remainder of the colon.
    The tissue samples is included in a paraffin block to extract thin sections of a few micrometers. After staining, these sections are examined under a microscope by a doctor specializing in pathology (or histology). This review classifies the sample according to the shape of the tumor and the type of cells.
    We found most often in the intestines of adenomas (adenomatous polyps =). Regarded as Benin, the polyp may develop into cancer if left in place, it is large (more than one centimeter in diameter), and / or is villous (= with villus). The small tubular polyps and polyps are less risky. There are also hyperplastic polyps considered virtually risk-free. Finally, we found in colon adenocarcinomas, which are the real cancers, including dysplastic cells crossing the lamina propria. This first stage of the invasion may evolve to spread to other organs and lead to the emergence of liver metastases in most cases causing death more frequently than the primary tumor.
    Today diagnostic imaging based on the use of CT scan or with the help of a technique for colonic distension. This particular technique justifies the specific term of CT colonography. Distention can be done with an enema with water or with gas insufflation.
    In the first case of water enema CT colonography talking about water. His statement is essentially a diagnosis of colorectal cancer and is proposed as an alternative to colonoscopy to symptoms suggestive of colon cancer, especially in elderly or frail to which it is preferable to dispense with a general anesthetic first intention. This technique allows the diagnosis of cancer and the comprehensive review of research of a metastasis, especially liver or lung.
    The second technique called virtual colonoscopy with CT colonography obtained by gaseous distention, preferably with carbon dioxide, is now a powerful alternative to colonoscopy for the diagnosis not only cancer but also for precancerous lesions, adenomas. This scanning method requires a booming bowel preparation prior to 48 hours, quite similar to that of colonoscopy. The scanner is externally without injection of contrast and with a very low radiation, up to 10 times lower than that of a typical abdominal scan. With precise control, in real time, the insufflation pressure risks of perforation are almost non-existent and in any case much lower than those of colonoscopy. A radiologist trained in this technique can achieve a detection rate of significant lesions, higher than that obtained by a colonoscopy because some lesions, particularly behind the folds, may be missed by colonoscopy. The CT colonography does not allow resection of a polyp but was shown on large series of patients that could, starting with CT, 90% reduction in the number of colonoscopies needed.

Treatment

When cancer is detected at an early stage, the cure (90% cure for stage I). If the cancer is discovered late, the chances of recovery are much lower (less than 5% healing stage IV). The first treatment is surgery, which removes the tumor and surrounding lymph nodes (lymphadenectomy). (Very superficial cancers are sometimes completely removed endoscopically, without additional surgery necessary if there is no crossing of the mucosal muscles). It combines adjuvant chemotherapy, if the lymph node contains metastases or if there is liver or lung metastases, radiotherapy if excision has been complete, with residual tumor on individual vital organs.
In the case of low rectal cancer, the presence of lymph nodes seen on CT or ultrasonography is an indication of preoperative chemoradiotherapy.

Related Posts

  1. One Response to “Colon Cancer”

  2. By Mallie Riek on Dec 17, 2011 | Reply

    I am not rattling excellent with English but I find this really leisurely to translate.

Post a Comment