- ACRONYMS AND DEFINITIONS
- ACG - American College of Gastroenterology
- ACS - American Cancer Society
- AGA - American Gastroenterological Association
- ASGE - American Society for Gastrointestinal Endoscopy
- CRC - Colorectal cancer
- FAP - Familial adenomatous polyposis
- USMSTF - U.S. Multi-Society Task Force on Colorectal Cancer which represents the ACG, AGA, and ASGE
- UC - Ulcerative colitis
- WHO - World Health Organization
- TERMINOLOGY
- Adenoma - general term for a benign tumor that originates from a gland. A gland is an organ that synthesizes a substance for secretion in the body. Colon polyps are often referred to as "adenomas."
- Adenomatous - Adjective that means "originating from a gland"
- Hyperplastic - Adjective that means "overgrowth of tissue or cells."
- Pancolitis - Inflammation of the entire colon
- Pedunculated - Attached to a surface by a stalk
- Polyp - A polyp is an abnormal growth of tissue originating from a mucous membrane. Polyps can be attached to the mucous membrane by a stalk (pedunculated), or attached directly to the surface (sessile).
- Serrated - Adjective that means "sawtooth pattern." Serrated polyps have a saw tooth pattern on their surface, and most of them sessile. Serrated polyps are subdivided into 3 groups (see polyp type below).
- Sessile - Adjective that means "attached directly to a surface" (no stalk)
- Tubular - Adjective that means "consisting of tubes." Most colonic adenomas are tubular with networks of branching adenomatous epithelium.
- Villous - Adjective that means "covered with villi." Villi are hair-like projections on the surface of a tissue. Villous adenomas carry a higher risk for developing into cancer. [1]
- COLON POLYPS (ADENOMAS)
- Overview
- All colon polyps are referred to as adenomas. Adenomas are subdivided into groups based on size, histology, and location. The risk that an adenoma will become cancerous is based on a combination of these 3 characteristics.
- The table below details the different types of adenomas based on size, histology, and location
Adenoma Characteristics |
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Size - Adenoma size is the most important predictor of cancer risk. The size of an adenoma is based on its diameter.
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Histology - Histology is the second most important factor in predicting cancer risk. In general, adenomas can be divided into two large groups based on their histology - conventional adenomas and serrated adenomas. Degree of dysplasia is another factor that affects cancer risk in both types of adenomas.
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Location
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- Prevalence
- Colon polyps are very common with a prevalence of up to 50% in people presenting for screening colonoscopy
- The table below gives the prevalence of CRC and polyps in a study where 4404 people at average risk for colon cancer had a screening colonoscopy performed. The average age of the patients in the study was 68.6 years and 44.6% were male.
Prevalence of CRC and Polyps in 4404 Patients at Average Risk for CRC who had a Screening Colonoscopy | |
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Finding | Prevalence |
CRC | 0.7% |
Advanced adenoma | 9.7% |
Tubular adenomas < 10 mm or hyperplastic polyps | 37% |
No polyp | 52.6% |
- CRC risk with colon polyps
- The current standard of care for colon polyps is polyp removal and surveillance with follow-up colonoscopy. This makes it difficult to study the natural course of polyps since they are typically removed.
- A handful of small studies have followed the natural course of colon polyps. These studies have typically been short with follow-up of 2 - 3 years. The longest study was a study published in the eighties that followed 226 patients with polyps ≥ 10 mm size with barium enemas for an average of 5.6 years. In that study, the risk of cancer at the polyp site at 5, 10, and 20 years was 2.5%, 8%, and 24%, respectively. [PMID 3653628]
- A large cohort study looked at the risk of CRC based on findings from the subject's first colonoscopy or flexible sigmoidoscopy (flex sig). Most of the endoscopies were done for routine screening, and a majority of the subjects had more than 2 surveillance endoscopies over a median follow-up of 10 years. The risk of CRC based on initial endoscopy findings is presented in the table below.
CRC Risk Based on Findings from Initial Colonoscopy/Flex sig | ||
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Finding | 5-year CRC Risk | 10-year CRC Risk |
Advanced adenoma | 0.6% | 1.7% |
Nonadvanced adenoma | 0.1% | 0.3% |
Serrated polyp ≥ 10 mm | 0.4% | 1.1% |
Serrated polyp < 10 mm | 0.1% | 0.4% |
No polyp | 0.2% | 0.4% |
- FAMILY HISTORY OF COLON CANCER/POLYPS
ACG 2021 Screening Recommendations Based on Family History |
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One first-degree relative with CRC or advanced polyp at age < 60 years, or ≥ 2 first-degree relatives with CRC or advanced polyp at any age
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One first-degree relative with CRC or advanced polyp at age ≥ 60 years
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One second-degree relative with CRC or advanced polyp
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AGA 2018 Screening Recommendations Based on Family History |
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One first-degree relative with CRC
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≥ 2 first-degree relatives with CRC
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≥ 1 second-degree relative with CRC
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≥ 1 first-degree relative with advanced adenoma
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≥ 1 first-degree relative with non-advanced adenoma or polyp of unknown histology
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USMSTF 2017 Screening Recommendations Based on Family History |
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Single first-degree relative with CRC or advanced adenoma diagnosed at age < 60 years or two first-degree relatives with CRC or
advanced adenomas diagnosed at any age
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Single first-degree relative with CRC or advanced adenoma diagnosed at age ≥ 60 years✝
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- Advanced adenoma is defined as having any of the following:
- ≥ 10 mm in size
- Adenoma with tubulovillous or villous histology
- Adenoma with high-grade dysplasia
- PERSONAL HISTORY OF COLON CANCER
- The AGA makes the following recommendations for surveillance after colon cancer surgical resection
- Colonoscopy 3 - 6 months after resection if no unresectable metastases are found during surgery
- Colonoscopy 1 year after resection
- If colonoscopy at 1 year is normal, then the interval before the next colonoscopy is 3 years
- If colonoscopy at 3 years is normal, then the interval before the next colonoscopy is 5 years
- Patients with rectal cancer who undergo low anterior resection may have periodic examinations of the rectum every 3 - 6 months for the first 2 - 3 years after surgery to check for local recurrence [3]
- NOTE: In some patients, other testing is indicated including annual CT scans of the chest and abdomen for 3 years, and CEA blood testing every 3 - 6 months for 2 - 3 years
- PERSONAL HISTORY OF COLON POLYPS
- Overview
- Post-colonoscopy follow-up recommendations from the USMSTF are divided into two groups depending on whether the polyps were conventional adenomas or serrated adenomas (see polyp types above)
- The first table gives recommendations for conventional adenomas and the second table is for serrated adenomas. If both types are found, the recommendation with the shortest follow-up should be used. See continued surveillance for recommendations on subsequent colonoscopies.
- All recommendations are for people who were at average risk before their screening colonoscopy
USMSTF Recommendations for Post-colonoscopy Follow-up of Conventional Adenomas | |
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Screening colonoscopy finding | Interval before first follow-up colonoscopy |
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7 - 10 years |
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3 - 5 years |
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3 years |
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3 years |
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3 years |
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3 years |
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1 year |
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6 months |
USMSTF Recommendations for Post-colonoscopy Follow-up of Serrated Polyps | |
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Screening colonoscopy finding | Interval before first follow-up colonoscopy |
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10 years |
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10 years |
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5 - 10 years |
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3 - 5 years |
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3 years |
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3 years |
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3 years |
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3 - 5 years |
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3 years |
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6 months |
- CONTINUED SURVEILLANCE AFTER FIRST FOLLOW-UP COLONOSCOPY
- Overview
- The recommendations below are for continued surveillance after the first follow-up colonoscopy for colon polyps
- Initial colonoscopy - first screening colonoscopy
- First follow-up colonoscopy - first colonoscopy done after the initial colonoscopy
1 - 4 tubular adenomas < 10 mm found on initial colonoscopy | |
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Findings on first follow-up colonoscopy | Recommended interval for next surveillance |
Normal | 10 years |
1 - 2 tubular adenomas < 10 mm | 7 - 10 years |
3 - 4 tubular adenomas < 10 mm | 3 - 5 years |
High-risk adenoma | 3 years |
High-risk adenoma found on initial colonoscopy | |
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Findings on first follow-up colonoscopy | Recommended interval for next surveillance |
Normal | 5 years |
1 - 2 tubular adenomas < 10 mm | 5 years |
3 - 4 tubular adenomas < 10 mm | 3 - 5 years |
High-risk adenoma | 3 years |
- High-risk adenoma(s) is defined as having any of the following:
- ≥ 10 mm in size
- Adenoma with tubulovillous/villous histology
- Adenoma with high-grade dysplasia
- 5 - 10 adenomas < 10 mm in size [14]
- CYSTIC FIBROSIS
- Overview
- The risk of colorectal cancer in patients with cystic fibrosis is 5 - 10 times greater than that of the general population. The risk is 25 - 30 times greater in patients who have had an organ transplant.
- In 2017, a multispecialty task force issued guidelines for colon cancer screening in patients with cystic fibrosis
- Colon cancer screening recommendations for patients with cystic fibrosis:
- Patients without organ transplant: start screening at age 40 with colonoscopy. Screen every 5 years.
- Patients with organ transplant: start screening at age 30 with colonoscopy. Screen within 2 years of organ transplant surgery. Screen every 5 years.
- All patients with adenomas should have a follow-up colonoscopy in 3 years, or sooner if indicated
- Patients should receive a cystic fibrosis-specific intensive bowel preparation [8]
- FAMILIAL ADENOMATOUS POLYPOSIS (FAP)
- The AGA makes the following recommendations for patients with FAP
- Colonoscopy at age 10 - 12 years
- Annual flexible sigmoidoscopy
- Colectomy if genetic testing is positive [3]
- HEREDITARY NONPOLYPOSIS COLON CANCER (LYNCH SYNDROME)
- NOTE: The name "hereditary nonpolyposis colon cancer" can be confusing. It is a condition that predisposes someone to colon cancer, but it does not mean the person has colon cancer.
- The AGA makes the following recommendations for patients with Lynch syndrome
- Begin colonoscopy at age 20 - 25 years, or 10 years before the youngest case in the immediate family
- Colonoscopy every 1 - 2 years and genetic testing [3]
- The ACG makes the following recommendations for patients with Lynch syndrome
- Begin colonoscopy at age 20 - 25 years
- Colonoscopy every 2 years until age 40 years, then annually
- Genetic testing [2]
- INFLAMMATORY BOWEL DISEASE (CROHN'S, ULCERATIVE COLITIS)
- Ulcerative colitis (ACG 2019 recommendations)
- Initial: Screen patients with UC of extent greater than the rectum with colonoscopy at 8 years after diagnosis
- Follow-up screening: Screen with colonoscopy every 1 - 3 years depending on UC severity and other risk factors for colon cancer
- Patients with UC and primary sclerosing cholangitis: Screen annually with colonoscopy
- Other methods of colon cancer screening (e.g. fecal DNA, CT colonography) are not recommended in UC patients [12]
- Crohn's disease (ASGE 2015 recommendations)
- The optimal colon cancer screening interval for patients with Crohn's disease has not been defined
- For patients with disease involving at least 1/3 of the colon, the screening guidelines for ulcerative colitis may applied
- For patients with disease involving < 1/3 of the colon, no consensus recommendation has been determined [7]
- SERRATED POLYPOSIS SYNDROME
- The WHO defines serrated polyposis syndrome as the presence of any of the following criteria:
- 1. At least 5 serrated polyps proximal to the sigmoid colon with at least two ≥ 1 cm in diameter
- 2. Any serrated polyps proximal to the sigmoid colon in an individual with a first-degree family member who has serrated polyposis syndrome
- 3. More than 20 serrated polyps of any size throughout the colon [1]
- The AGA makes the following recommendations for patients with serrated polyposis syndrome
- Annual colonoscopy [1]
- BIBLIOGRAPHY
- 1 - PMID 22763141 - AGA GL 2012
- 2 - PMID 19240699 - ACG GL 2009
- 3 - PMID 18384785 - AGA GL 2008
- 4 - PMID 20068560 - ACG GL on UC 2010
- 5 - PMID 16564852 - ASGE IBD GL 2006
- 6 - PMID 19174807 - ACG GL on Crohn's 2009
- 7 - PMID 25800660 - ASGE 2015 GL
- 8 - PMID 29289528 - Cystic Fibrosis Colorectal Cancer Screening Consensus Recommendations, Gastroenterology, (2017)
- 9 - American Cancer Society website
- 10 - PMID 28600072 - Colorectal Cancer Screening: Recommendations for Physicians and Patients From the U.S. Multi-Society Task Force on Colorectal Cancer, Gastroenterology (2017)
- 11 - PMID 30121253 - Clinical Practice Guideline on Screening for Colorectal Cancer in Individuals With a Family History of Nonhereditary Colorectal Cancer or Adenoma: The Canadian Association of Gastroenterology Banff Consensus, Gastroenterology (2018)
- 12 - PMID 30840605 - ACG Clinical Guideline: Ulcerative Colitis in Adults, Am J Gastroenterol (2019)
- 13 - PMID 22710576 - Serrated Lesions of the Colorectum: Review and Recommendations From an Expert Panel, Am J Gastroenterol (2012)
- 14 - PMID 32044106 - Recommendations for Follow-Up After Colonoscopy and Polypectomy: A Consensus Update by the US Multi-Society Task Force on Colorectal Cancer, Gastroenterology (2020)
- 15 - PMID 15616205 - Fecal DNA versus Fecal Occult Blood for Colorectal-Cancer Screening in an Average-Risk Population, NEJM (2004)
- 16 - PMID 18691580 - Polyp Size and Advanced Histology in Patients Undergoing Colonoscopy Screening: Implications for CT Colonography, Gastroenterology (2008)
- 17 - PMID 23746988 - Assessment of Volumetric Growth Rates of Small Colorectal Polyps With CT Colonography: A Longitudinal Study of Natural History, Lancet Oncology (2013)
- 18 - PMID 31302144 - Long-term Risk of Colorectal Cancer After Removal of Conventional Adenomas and Serrated Polyps, Gastroenterology (2019)
- 19 - PMID 33657038 - ACG Clinical Guidelines: Colorectal Cancer Screening, Am J Gastroenterol (2021)