Colorectal cancer
Pathophysiology
Colorectal cancer probably arises from colorectal polyps.[1] Adenomatous polyps convert to cancers at a rate of about 1% per year.[2]
Treatment
Medications
- Cetuximab
Cetuximab, an IgG1 chimeric monoclonal antibody against epidermal growth factor receptor, may help according to a randomized controlled trial.[3]
Screening
A clinical practice guideline jointly written by the American Cancer Society and other groups recommends one of:[4]
- Flexible sigmoidoscopy every 5 years
- Barium enema every 5 years
- Virtual colonography (a noninvasive test based on computed tomography) every 5 years
- Colonoscopy every 10 years
When polyps are found, a clinical practice guideline jointly written by the American Cancer Society and other groups states:[5]
- High risk polyps are 1) 3 or more synchronous adenomas, 2) adenomas ≥1 cm in diameter, or 3) villous histology or high-grade dysplasia.
- High risk polyps should have follow-up colonoscopy in 3 years
- Low risk polyps should have repeat colonoscopy in 5 to 10 years
- If no adenomas are found, follow-up evaluation should be at 10 years
A validation of these guidelines found:[6]
- High risk adenomas - 9% of an advanced adenoma at 4 years of follow-up.
- Low risk adenomas - 5% of an advanced adenoma at 4 years of follow-up.
Prevention
Aspirin chemoprophylaxis
A clinical practice guideline by the U.S. Preventive Services Task Force (USPSTF) recommended against taking aspirin (grade D recommendation).[7] The Task Force acknowledged that aspirin may reduce the incidence of colorectal cancer, but "concluded that harms outweigh the benefits of aspirin and NSAID use for the prevention of colorectal cancer". A subsequent meta-analysis 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".[8] However, long-term doses over 81 mg per day may increase bleeding events.[9]
Calcium
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.".[10] Subsequently, one randomized controlled trial by the Women's Health Initiative (WHI) reported negative results.[11] A second randomized controlled trial reported reduction in all cancers, but had insufficient colorectal cancers for analysis.[12]
References
- ↑ Levine JS, Ahnen DJ (December 2006). "Clinical practice. Adenomatous polyps of the colon". N. Engl. J. Med. 355 (24): 2551–7. DOI:10.1056/NEJMcp063038. PMID 17167138. Research Blogging.
- ↑ Stryker SJ, Wolff BG, Culp CE, Libbe SD, Ilstrup DM, MacCarty RL (November 1987). "Natural history of untreated colonic polyps". Gastroenterology 93 (5): 1009–13. PMID 3653628. [e]
- ↑ Jonker DJ, O'Callaghan CJ, Karapetis CS, et al (2007). "Cetuximab for the treatment of colorectal cancer". N. Engl. J. Med. 357 (20): 2040–8. DOI:10.1056/NEJMoa071834. PMID 18003960. Research Blogging.
- ↑ Levin, B., Lieberman, D. A., McFarland, B., Smith, R. A., Brooks, D., Andrews, K. S., et al. (2008). Screening and surveillance for the early detection of colorectal cancer and adenomatous polyps, 2008: a joint guideline from the American Cancer Society, the US Multi-society Task Force on Colorectal Cancer, and the American College of Radiology. CA Cancer J Clin, CA.2007.0018. DOI:10.3322/CA.2007.0018.
- ↑ Winawer SJ, Zauber AG, Fletcher RH, et al (May 2006). "Guidelines for colonoscopy surveillance after polypectomy: a consensus update by the US Multi-Society Task Force on Colorectal Cancer and the American Cancer Society". Gastroenterology 130 (6): 1872–85. DOI:10.1053/j.gastro.2006.03.012. PMID 16697750. Research Blogging.
- ↑ Laiyemo AO, Murphy G, Albert PS, et al (March 2008). "Postpolypectomy colonoscopy surveillance guidelines: predictive accuracy for advanced adenoma at 4 years". Ann. Intern. Med. 148 (6): 419–26. PMID 18347350. [e]
- ↑ (2007) "Routine aspirin or nonsteroidal anti-inflammatory drugs for the primary prevention of colorectal cancer: U.S. Preventive Services Task Force recommendation statement". Ann. Intern. Med. 146 (5): 361-4. pmid=17339621. [e] PMID 17339621
- ↑ Flossmann E, Rothwell PM (2007). "Effect of aspirin on long-term risk of colorectal cancer: consistent evidence from randomised and observational studies". Lancet 369 (9573): 1603-13. DOI:10.1016/S0140-6736(07)60747-8. PMID 17499602. Research Blogging. PMID 17499602
- ↑ Campbell CL, Smyth S, Montalescot G, Steinhubl SR (2007). "Aspirin dose for the prevention of cardiovascular disease: a systematic review". JAMA 297 (18): 2018-24. DOI:10.1001/jama.297.18.2018. PMID 17488967. Research Blogging. PMID 17488967
- ↑ Weingarten MA, Zalmanovici A, Yaphe J (2005). "Dietary calcium supplementation for preventing colorectal cancer and adenomatous polyps". Cochrane database of systematic reviews (Online) (3): CD003548. DOI:10.1002/14651858.CD003548.pub3. PMID 16034903. Research Blogging.
- ↑ Wactawski-Wende J, Kotchen JM, Anderson GL, et al (2006). "Calcium plus vitamin D supplementation and the risk of colorectal cancer". N. Engl. J. Med. 354 (7): 684-96. DOI:10.1056/NEJMoa055222. PMID 16481636. Research Blogging.
- ↑ Lappe JM, Travers-Gustafson D, Davies KM, Recker RR, Heaney RP (2007). "Vitamin D and calcium supplementation reduces cancer risk: results of a randomized trial". Am. J. Clin. Nutr. 85 (6): 1586-91. PMID 17556697. [e]