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, also called '''colon cancer''' or '''bowel cancer''', includes
Cancer ous growths in the
Colon ,
Rectum and
Appendix . It is the third most common form of cancer and the second leading cause of cancer-related death in the Western world. Colorectal cancer causes 655,000 deaths worldwide per year.
1 Many colorectal cancers are thought to arise from
Adenoma tous
Polyp s in the colon. These mushroom-like growths are usually
Benign , but some may develop into cancer over time. The majority of the time, the diagnosis of localized colon cancer is through
Colonoscopy . Therapy is usually through surgery, which in many cases is followed by
Chemotherapy .
Colon cancer often causes no symptoms until it has reached a relatively advanced stage. Thus, many organizations recommend periodic screening for the disease with
Fecal Occult Blood testing and colonoscopy. When symptoms do occur, they depend on the site of the lesion. Generally speaking, the nearer the lesion is to the anus, the more bowel symptoms there will be, such as:
- Change in bowel habits
- --- change in frequency ( Constipation and/or Diarrhea ),
- --- change in the quality of stools
- --- change in consistency of stools
- Bloody Stools or rectal bleeding
- Stools with mucus
- Tarry stools ( Melena ) (more likely related to upper gastrointestinal eg stomach or duodenal disease)
- Feeling of incomplete defecation ( Tenesmus ) (usually associated with rectal cancer)
- Reduction in diameter of feces
- Bowel Obstruction (rare)
Especially in the cases of cancer in the ascending colon, sometimes only the less specific constitutional symptoms will be found:
- Anemia , with symptoms such as dizziness, malaise and palpitations. Clinically there will be Pallor and a complete blood picture will confirm the low hemoglobin level.
- Anorexia
- Asthenia , weakness
- Unexplained weight loss.
There may also be symptoms attributed to distant
Metastasis :
- Shortness of breath as in lung metastasis
- Epigastric or right upper quadrant pain, as in liver metastasis. Rarely can there be Jaundice if the outflow of Bile is blocked. Clinically there might be Liver Enlargement .
The lifetime risk of developing colon cancer in the United States is about 7%. Certain factors increase a person's risk of developing the disease. These include:
- Age. The risk of developing colorectal cancer increases with age. Most cases occur in the 60s and 70s, while cases before age 50 are uncommon unless a family history of early colon cancer is present.
- Polyps of the colon, particularly adenomatous polyps, are a risk factor for colon cancer. The removal of colon polyps at the time of colonoscopy reduces the subsequent risk of colon cancer.
- History of cancer. Individuals who have previously been diagnosed and treated for colon cancer are at risk for developing colon cancer in the future. Women who have had cancer of the ovary, uterus, or breast are at higher risk of developing colorectal cancer.
- Heredity:
- --- Family history of colon cancer, especially in a close relative before the age of 55 or multiple relatives
- --- Familial Adenomatous Polyposis (FAP) carries a near ''100%'' risk of developing colorectal cancer by the age of 40 if untreated
- --- Hereditary Nonpolyposis Colorectal Cancer (HNPCC) or Lynch syndrome
- Long-standing Ulcerative Colitis or Crohn's Disease of the colon, approximately 30% after 25 years if the entire colon is involved
- Smoking. Smokers are more likely to die of colorectal cancer than non-smokers. An American Cancer Society study found that "Women who smoked were more than 40% more likely to die from colorectal cancer than women who never had smoked. Male smokers had more than a 30% increase in risk of dying from the disease compared to men who never had smoked." {Link without Title}
- Diet. Studies show that a diet high in red meatChao A, Thun MJ, Connell CJ, McCullough ML, Jacobs EJ, Flanders WD, Rodriguez C, Sinha R, Calle EE. ''Meat consumption and risk of colorectal cancer.'' JAMA 2005;293:172-82. PMID 15644544. and low in fresh fruit, vegetables, poultry and fish increases the risk of colorectal cancer. In June 2005, a study by the European Prospective Investigation Into Cancer And Nutrition suggested that diets high in red and processed meat, as well as those low in fiber, are associated with an increased risk of colorectal cancer. Individuals who frequently ate fish showed a decreased risk. However, other studies have cast doubt on the claim that diets high in fiber decrease the risk of colorectal cancer; rather, low-fiber diet was associated with other risk factors, leading to confounding.Park Y, Hunter DJ, Spiegelman D, Bergkvist L, Berrino F ''et al''. [http://jama.ama-assn.org/cgi/content/abstract/294/22/2849 Dietary fiber intake and risk of colorectal cancer: a pooled analysis of prospective cohort studies . ''JAMA'' 2005;294:2849-57. PMID 16352792. The nature of the relationship between dietary fiber and risk of colorectal cancer remains controversial.
- Physical inactivity. People who are physically active are at lower risk of developing colorectal cancer.
- Virus. Exposure to some viruses (such as particular strains of Human Papilloma Virus ) may be associated with colorectal cancer.
- Alcohol. See the subsection below.
- Primary Sclerosing Cholangitis offers a risk independent to Ulcerative Colitis
- Low Selenium .
On its colorectal cancer page, the (NCI) Cancer Trends Progress Report
Alcohol Consumption
The NIAAA reports that, "Epidemiologic studies have found a small but consistent dose-dependent association between alcohol consumption and colorectal cancerLongnecker, M.P. Alcohol consumption in relation to risk of cancers of the breast and large bowel. ''Alcohol Health & Research World'' ''16(3)':223-229, 1992.Longnecker, M.P.; Orza, M.J.; Adams, M.E.; Vioque, J.; and Chalmers, T.C.
A meta-analysis of alcoholic beverage consumption in relation to risk of colorectal cancer ''Cancer Causes and Control'' ''1(1)'':59-68, 1990.even when controlling for fiber and other dietary factors.Kune, S.; Kune, G.A.; and Watson, L.F.
Case-control study of alcoholic beverages as etiological factors: The Melbourne Colorectal Cancer Study ''Nutrition and Cancer'' ''9(1)'':43-56, 1987.Potter, J.D., and McMichael, A.J.
Diet and cancer of the colon and rectum: A case-control study ''Journal of the National Cancer Institute'' ''76(4)'':557-569, 1986. Despite the large number of studies, however, causality cannot be determined from the available data."
National Institute On Alcohol Abuse And Alcoholism Alcohol and Cancer - Alcohol Alert No. 21-1993
"Heavy alcohol use may also increase the risk of colorectal cancer" (NCI). One study found that "People who drink more than 30 grams of alcohol per day (and especially those who drink more than 45 grams per day) appear to have a slightly higher risk for colorectal cancer."
Alcohol Consumption and the Risk for Colorectal Cancer 20 April 2004
Alcohol Intake and Colorectal Cancer: A Pooled Analysis of 8 Cohort Studies Another found that "The consumption of one or more alcoholic beverages a day at baseline was associated with approximately a 70% greater risk of colon cancer."Boston University
"Alcohol May Increase the Risk of Colon Cancer" Su LJ, Arab L.
Alcohol consumption and risk of colon cancer: evidence from the National Health and Nutrition Examination Survey I Epidemiologic Follow-Up Study . ''Nutr and Cancer''. 2004;50(2):111–119.Cho E, Smith-Warner SA, Ritz J, van den Brandt PA, Colditz GA, Folsom AR, Freudenheim JL, Giovannucci E, Goldbohm RA, Graham S, Holmberg L, Kim DH, Malila N, Miller AB, Pietinen P, Rohan TE, Sellers TA, Speizer FE, Willett WC, Wolk A, Hunter DJ
Alcohol intake and colorectal cancer: a pooled analysis of 8 cohort studies ''Ann Intern Med'' 2004 Apr 20;140(8):603-13
One study found that "While there was a more than twofold increased risk of significant colorectal neoplasia in people who drink spirits and beer, people who drank wine had a lower risk. In our sample, people who drank more than eight servings of beer or spirits per week had at least a one in five chance of having significant colorectal neoplasia detected by screening colonoscopy.".Joseph C. Anderson, Zvi Alpern, Gurvinder Sethi, Catherine R. Messina, Carole Martin, Patricia M. Hubbard, Roger Grimson, Peter F. Ells, and Robert D. Shaw
Prevalence and Risk of Colorectal Neoplasia in Consumers of Alcohol in a Screening Population ''Am J Gastroenterol'' Volume 100 Issue 9 Page 2049 Date September 2005
Other research suggests that "to minimize your risk of developing colorectal cancer, it's best to drink in moderation"
Drinking may be a cause of earlier onset of colorectal cancer.Brown, Anthony J.
Alcohol, tobacco, and male gender up risk of earlier onset colorectal cancer
image of identified in sigmoid
Colon on screening
Colonoscopy in the setting of
Crohn's Disease .]]
Colorectal cancer can take many years to develop and early detection of colorectal cancer greatly improves the chances of a cure. Therefore, screening for the disease is recommended in individuals who are at increased risk. There are several different tests available for this purpose.
- Digital Rectal Exam (DRE): The doctor inserts a lubricated, gloved finger into the rectum to feel for abnormal areas. It only detects tumors large enough to be felt in the distal part of the rectum and is not really a screening test.
- Fecal Occult Blood test (FOBT): a test for blood in the stool.
- Endoscopy :
- --- Sigmoidoscopy : A lighted probe (sigmoidoscope) is inserted into the rectum and lower colon to check for polyps and other abnormalities.
- --- s and other abnormalities that may be caused by cancer. A colonoscopy has the advantage that if Polyp s are found during the procedure they can be immediately removed. Tissue can also be taken for Biopsy .
In the United States, colonoscopy or FOBT plus sigmoidoscopy are the preferred screening options.
- Double contrast barium enema (DCBE): First, an overnight preparation is taken to cleanse the colon. An Enema containing Barium Sulfate is administered, then air is insufflated into the colon, distending it. The result is a thin layer of barium over the inner lining of the colon which is visible on X-ray films. A cancer or a precancerous polyp can be detected this way. This technique can miss the (less common) flat polyp.
- Virtual Colonoscopy replaces X-ray films in the double contrast barium enema (above) with a special Computed Tomography scan and requires special workstation software in order for the Radiologist to interpret. This technique is approaching Colonoscopy in sensitivity for polyps. However, any polyps found must still be removed by standard colonoscopy.
- Standard Computed Axial Tomography is an x-ray method that can be used to determine the degree of spread of cancer, but is not sensitive enough to use for screening. Some cancers are found in CAT scans performed for other reasons.
- can give an indication of tumor load. In particular, high levels of Carcinoembryonic Antigen (CEA) in the blood can indicate Metastasis of Adenocarcinoma . These tests are frequently False Positive or False Negative , and are not recommended for screening.
- Genetic Counseling and Genetic Testing for families who may have a hereditary form of colon cancer, such as Hereditary Nonpolyposis Colorectal Cancer (HNPCC) or Familial Adenomatous Polyposis (FAP).
- Positron Emission Tomography (PET) is a 3-dimensional scanning technology where a radioactive sugar is injected into the patient, the sugar collects in tissues with high metabolic activity, and an image is formed by measuring the emission of radiation from the sugar. Because cancer cells often have very high metabolic rate, this can be used to differentiate benign and malignant tumors. PET is not used for screening and does not (yet) have a place in routine workup of colorectal cancer cases.
- Whole-Body PET imaging is the most accurate diagnostic test for detection of recurrent colorectal cancer, and is a cost-effective way to differentiate resectable from non-resectable disease. A PET scan is indicated whenever a major management decision depends upon accurate evaluation of tumour presence and extent.
- Stool DNA testing is an emerging technology in screening for colorectal cancer. Pre-malignant adenomas and cancers shed DNA markers from their cells which are not degraded during the digestive process and remain stable in the stool. Capture, followed by Polymerase Chain Reaction amplifies the DNA to detectable levels for assay. Clinical studies have shown a cancer detection sensitivity of 71%-91%. 2
The
Pathology of the tumor is usually reported from the analysis of tissue taken from a biopsy or surgery. A pathology report will usually contain a description of
Cell Type and grade. The most common colon cancer cell type is
Adenocarcinoma which accounts for 95% of cases. Other, rarer types include
Lymphoma and
Squamous Cell Carcinoma .
Cancers on the right side (ascending colon and
Cecum ) tend to be exophytic, that is, the tumour grows outwards from one location in the bowel wall. This very rarely causes obstruction of
Feces , and presents with symptoms such as
Anemia . Left-sided tumours tend to be circumferential, and can obstruct the bowel much like a napkin ring.
''Histopathology'': Adenocarcinoma is a malignant epithelial tumor, originating from glandular epithelium of the colorectal mucosa. It invades the wall, infiltrating the
Muscularis Mucosae , the
Submucosa and thence the muscularis propria. Tumor cells describe irregular tubular structures, harboring pluristratification, multiple lumens, reduced stroma ("back to back" aspect). Sometimes, tumor cells are discohesive and secrete mucus, which invades the interstitium producing large pools of mucus/colloid (optically "empty" spaces) - ''mucinous (colloid)'' adenocarcinoma, poorly differentiated. If the mucus remains inside the tumor cell, it pushes the nucleus at the periphery - "signet-ring cell." Depending on glandular architecture, cellular pleomorphism, and mucosecretion of the predominant pattern, adenocarcinoma may present three degrees of differentiation: well, moderately, and poorly differentiated.
1
Colon cancer staging is an estimate of the amount of penetration of a particular cancer. It is performed for diagnostic and research purposes, and to determine the best method of treatment. The systems for staging colorectal cancers largely depend on the extent of local invasion, the degree of lymph node involvement and whether there is distant
Metastasis .
Definitive staging can only be done after
Surgery has been performed and pathology reports reviewed. An exception to this principle would be after a colonoscopic polypectomy of a malignant pedunculated polyp with minimal invasion. Preoperative staging of rectal cancers may be done with
Endoscopic Ultrasound . Adjuncts to staging of metastasis include
Abdominal Ultrasound ,
CT ,
PET Scanning , and other imaging studies.
Dukes' classification, first proposed by Dr Cuthbert E. Dukes in 1932, identifies the stages as:Dukes CE. The classification of cancer of the rectum. ''Journal of Pathological Bacteriology'' 1932;35:323.
- A - Tumour confined to the intestinal wall
- B - Tumour invading through the intestinal wall
- C - With lymph node(s) involvement
- D - With distant metastasis
The most common current staging system is the
TNM system, though many doctors still use the older Dukes system. The
TNM system assigns a number:
- T - The degree of invasion of the intestinal wall
- --- T0 - no evidence of tumor
- --- Tis- cancer in situ (tumor present, but no invasion)
- --- T1 - invasion through submucosa into lamina propria (basement membrane invaded)
- --- T2 - invasion into the muscularis propria (i.e. proper muscle of the bowel wall)
- --- T3 - invasion through the Muscularis Propria
- --- T4 - invasion of surrounding structures (e.g. bladder) or with tumour cells on the free external surface of the bowel
- N - the degree of Lymphatic node involvement
- --- N0 - no Lymph Node s involved
- --- N1 - one to three nodes involved
- --- N2 - four or more nodes involved
- M - the degree of Metastasis
- --- M0 - no metastasis
- --- M1 - metastasis present
The stage of a cancer is usually quoted as a number I, II, III, IV derived from the TNM value grouped by prognosis; a higher number indicates a more advanced cancer and a likely worse outcome.
- Stage 0
- --- Tis, N0, M0
- Stage I
- --- T1, N0, M0
- --- T2, N0, M0
- Stage IIA
- --- T3, N0, M0
- Stage IIB
- --- T4, N0, M0
- Stage IIIA
- --- T1, N1, M0
- --- T2, N1, M0
- Stage IIIB
- --- T3, N1, M0
- --- T4, N1, M0
- Stage IIIC
- --- Any T, N2, M0
- Stage IV
- --- Any T, Any N, M1
Colorectal cancer is a disease originating from the
Epithelial Cells lining the
Gastrointestinal Tract .
Hereditary or
Somatic Mutation s in specific
DNA sequences, among which are included
DNA Replication or
DNA Repair Gene s
3, and also the
APC ,
K-Ras ,
NOD2 and
P53 genes, lead to unrestricted cell division. The exact reason why (and whether) a diet high in fiber might prevent colorectal cancer remains uncertain. Chronic inflammation, as in
Inflammatory Bowel Disease , may predispose patients to malignancy.
The treatment depends on the staging of the cancer. When colorectal cancer is caught at early stages (with little spread) it can be curable. However when it is detected at later stages (when distant
Metastases are present) it is less likely to be curable.
Surgery remains the primary treatment while chemotherapy and/or radiotherapy may be recommended depending on the individual patient's staging and other medical factors.
Surgeries can be categorised into curative, palliative, bypass, fecal diversion, or open-and-close.
Surgical treatment can be offered if the tumor is localized.
- Very early cancer that develops within a Polyp can often be cured by removing the polyp (i.e., polypectomy) at the time of Colonoscopy .
- In colon cancer, a more advanced tumor typically requires surgical removal of the section of colon containing the tumor with sufficient margins, and radical en-bloc resection of Mesentery and Lymph Node s to reduce local recurrence (i.e., colectomy). If possible, the remaining parts of colon are Anastomosed together to create a functioning colon. In cases when anastomosis is not possible, a Stoma (artificial orifice) is created.
- Curative surgery on rectal cancer includes Total Mesorectal Excision (anterior resection) or abdominoperineal excision.
In case of multiple metastases, (non curative)
Resection of the primary tumor is still offered in order to reduce further
Morbidity caused by tumor bleeding, invasion, and its catabolic effect. Surgical removal of isolated liver metastases is, however, common and may be curative in selected patients; improved
Chemotherapy has increased the number of patients who are offered surgical removal of isolated liver metastases.
If the tumor invaded into adjacent vital structures which makes
Excision technically difficult, the surgeons may prefer to the tumor (ileotransverse bypass) or to do a proximal '''fecal diversion''' through a
Stoma .
The worst case would be an surgery, when surgeons find the tumor unresectable and the small bowel involved; any more procedures would do more harm than good to the patient. This is uncommon with the advent of laparoscopy and better radiological imaging. Most of these cases formerly subjected to "open and close" procedures are now diagnosed in advance and surgery avoided.
Laparoscopic -assisted
Colectomy is a
Minimally-invasive technique that can reduce the size of the incision, minimize the risk of infection, and reduce post-operative pain.
Cleveland Clinic colorectal surgeons developed the “no touch” technique to prevent the spread of cancer cells during colorectal surgery.http://www.universitycircle.org/content/healthcare.asp
As with any surgical procedure, colorectal surgery may result in complications including
Chemotherapy is used to reduce the likelihood of metastasis developing, shrink tumor size, or slow tumor growth. Chemotherapy is often applied after surgery (adjuvant), before surgery (neo-adjuvant), or as the primary therapy if surgery is not indicated (palliative). The treatments listed here have been shown in
Clinical Trial s to improve survival and/or reduce mortality rate and have been approved for use by the
US Food And Drug Administration .
Radiotherapy is not used routinely in colon cancer, as it could lead to
Radiation Enteritis , and it is difficult to target specific portions of the colon. It is more common for radiation to be used in rectal cancer, since the rectum does not move as much as the colon and is thus easier to target. Indications include:
- Colon cancer
- --- pain relief and palliation - targeted at Metastatic tumor deposits if they compress vital structures and/or cause pain
- Rectal cancer
- --- neoadjuvant - given before surgery in patients with tumors that extend outside the rectum or have spread to regional lymph nodes, in order to decrease the risk of recurrence following surgery or to allow for less invasive surgical approaches (such as a low anterior resection instead of an abdomino-perineal resection)
- --- adjuvant - where a tumor perforates the rectum or involves regional lymph nodes (AJCC T3 or T4 tumors or Duke's B or C tumors)
- --- palliative - to decrease the tumor burden in order to relieve or prevent symptoms
Sometimes chemotherapy agents are used to increase the effectiveness of radiation by sensitizing tumor cells if present.
Bacillus Calmette-Guérin (BCG) is being investigated as an adjuvant mixed with autologous tumor cells in immunotherapy for colorectal cancer.Mosolits S, Nilsson B, Mellstedt H. ''Towards therapeutic vaccines for colorectal carcinoma: a review of clinical trials.'', Expert Rev. Vaccines, 2005;4:329-50. PMID 16026248.
In and specialises in the development of
Gene-based Treatment s. Further vaccine trials are underway.
According to the American Cancer Society statistics in 2006
{Link without Title} greater then 20% of patients present with metastatic (stage IV) colorectal cancer at the time of diagnosis, and up to 25% of this group will have isolated liver metastasis that is potentially resectable. Lesions which undergo curative resection have demonstrated 5-year survival outcomes now exceeding 50%. Simmonds PC, et al. Surgical Resection of hepatic metastasis from colorectal cancer: A systemic review of published studies. Br J Surg. 2006;94:982-999. PMID 16538219
Resectability of a liver met is determined using preoperative imaging studies (Ct or MRI), intraoperative ultrasound, and by direct palpation and visualization during resection. Lesions confined to the right lobe are amenable to en bloc removal with a right hepatectomy (liver resection) surgery. Smaller lesions of the central or left liver lobe may sometimes be resected in anatomic "segments", while large lesions of left hepatic lobe are resected by a procedure call hepatic trisegmentectomy. Treatment of lesions by smaller,non-anatomic "wedge" resections is associated with higher recurrence rates. Some lesions which are not initially amenable to surgical resection may become candidates if they have signifigant responses to preoperative chemotherapy or immunotherapy regimines. Lesions which are not amenable to surgical resection for cure can be treated with modalities including radio-frequency ablation (RFA), cryoablation, and chemoembolization.
Patients with colon cancer and metastatic disease to the liver may be treated in either a single surgery or in staged surgeries (with the colon tumor traditionally removed first) depending upon the fitness of the patient for prolonged surgery, the difficulty expected with the procedure with either the colon or liver resection, and the comfort of the surgery performing potentially complex hepatic surgery.
Poor pronostic factors of patients with liver metastasis include
- Synchronous (diagnosed simultaneously) liver and primary colorectal tumors
- A short time between detecting the primary cancer and subsequent development of liver mets
- Multiple metastatic lesions
- High blood levels of the tumor marker, carcino-embryonic antigen (), in the patient prior to resection
- Larger size metastatic lesions
Cancer diagnosis very often results in an enormous change in the patient's psychological wellbeing. Various support resources are available from hospitals and other agencies which provide
Counseling , social service support,
Cancer Support Group s, and other services. These services help to mitigate some of the difficulties of integrating a patient's medical complications into other parts of their life.
Survival is directly related to detection and the type of cancer involved. Survival rates for early stage detection is about 5 times that of late stage cancers. CEA level is also directly related to the prognosis of disease, since its level correlates with the bulk of tumor tissue.
Follow-up aims at diagnosing metachronous lesion(s) or distant metastasis in the early stage. History taking and physical examination every 3 to 6 months for three years after surgery. CEA every 2 to 3 months for two or more years in patients who have had resection of liver metastasis. Colonoscopy looking for synchronise lesion(s) should be done shortly after surgery if preoperatively the scope cannot pass through the tumor; otherwise it should be done every 3 to 5 years.
ASCO recommends against other routine follow-up tests such as Chest X-Ray, Ultrasound, CT, etc.
Most colorectal cancers should be preventable, through increased surveillance, improved lifestyle, and, probably, the use of dietary chemopreventative agents.
Most colorectal cancer arise from adenomatous polyps. These lesions can be detected and removed during colonoscopy. Studies show this procedure would decrease by > 80% the risk of cancer death, provided it is started by the age of 50, and repeated every 5 or 10 years.Winawer SJ, Zauber AG, Ho MN, O'Brien MJ, Gottlieb LS, Sternberg SS, Waye JD, Schapiro M, Bond JH, Panish JF, Ackroyd F, Shike M, Kurtz RC, Hornsby-Lewis L, Gerdes H, Stewart ET, The National Polyp Study Workgroup. ''Prevention of colorectal cancer by colonoscopic polypectomy.''
N Engl J Med 1993;329:1977-81. PMID 8247072.
As per current guidelines under
National Comprehensive Cancer Network , in average risk individuals with negative family history of colon cancer and personal history negative for
Adenomas or
Inflammatory Bowel Diseases , flexible sigmoidoscopy every 5 years with fecal occult blood testing annually or double contrast barium enema are other options acceptable for screening rather than colonoscopy every 10 years (which is currently the Gold-Standard of care).
The comparison of colorectal cancer incidence in various countries strongly suggests that sedentarity, overeating (i.e., high caloric intake), and perhaps a diet high in meat (red or processed) could increase the risk of colorectal cancer. In contrast, physical exercise, and eating plenty of fruits and vegetables would decrease cancer risk, probably because they contain protective phytochemicals. Accordingly, lifestyle changes could decrease the risk of colorectal cancer as much as 60-80%.Cummings JH, Bingham SA. ''Diet and the prevention of cancer.''
BMJ 1998;317:1636-40.
Fulltext . PMID 9848907.
More than 200 agents, including the above cited phytochemicals, and other food components like calcium or folic acid (a B vitamin), and
NSAID s like aspirin, are able to decrease carcinogenesis in preclinical models: Some studies show full inhibition of carcinogen-induced tumours in the colon of rats. Other studies show strong inhibition of spontaneous intestinal polyps in mutated mice (Min mice). Chemoprevention clinical trials in human volunteers have shown smaller prevention, but few intervention studies have been completed today. Calcium, aspirin and celecoxib supplements, given for 3 to 5 years after the removal of a polyp, decreased the recurrence of polyps in volunteers (by 15-40%). The "chemoprevention database" shows the results of all published scientific studies of chemopreventive agents, in people and in animals.
4
Aspirin should not be taken routinely to prevent colorectal cancer, even in people with a family history of the disease, because the risk of bleeding and kidney failure from high dose aspirin (300mg or more) outweigh the possible benefits.
5
A concluded "300 mg or more of aspirin a day for about 5 years is effective in primary prevention of colorectal cancer in randomised controlled trials, with a latency of about 10 years".
7 PMID 17499602 However, long-term doses over 81 mg per day may increase bleeding events.
8 PMID 17488967
A
Meta-analysis by the
Cochrane Collaboration of
Randomized Controlled Trials published through 2002 concluded "Although the evidence from two RCTs suggests that calcium supplementation might contribute to a moderate degree to the prevention of colorectal adenomatous polyps, this does not constitute sufficient evidence to recommend the general use of calcium supplements to prevent colorectal cancer.".
9 Subsequently, one
Randomized Controlled Trial by the
Women's Health Initiative (WHI) reported negative results.
10 A second
Randomized Controlled Trial reported reduction in all cancers, but had insufficient colorectal cancers for analysis.
11
Colorectal cancer has been for years subject of mathematical modeling.
12 Full text For a comprehensive overview of current computational approaches on colorectal cancer see the
Integrative Biology web page.
