Colorectal cancer is a carcinoma arising from the luminal surface of the colon.
It is the 2nd most common cancer in women and third most common cancer in male worldwide. It commonly arises from adenomatous polyps.
It is strongly linked to age with 83% occurring in people ≥60 years old.
Rectal cancer is defined as cancerous lesions located within 12 cm of the anal verge.


Colorectal Screening

  • Primary goals are colorectal cancer prevention & early detection
  • Substantially reduces mortality rates in individuals between the age of 50 to 70 year 
  • May either be done among high-risk groups (eg those with IBD or with adenomatous polyps) or to the general population
  • No single screening test is 100% sensitive
  • Screening IBD patients helps detect colorectal cancer at an earlier stage but does not reduce mortality from colorectal cancer

Screening for the General Population

  • Colonoscopy
    • Best screening modality for high risk patients & best follow-up strategy for evaluating patients with positive gFOBT
    • Only screening test shown to reduce the incidence of colorectal cancer among screened individuals
    • Advantages include its wide availability, it allows single-session diagnosis & treatment, ability to examine entire colon, comfortable when done with sedation, & is the only test recommended at 10-year intervals
    • Interval for colonoscopy depends on factors such as family history of colorectal cancer (especially in 1st-degree relatives <50 years old), age at colitis diagnosis, presence of primary sclerosing cholangitis (PSC) & severity of inflammation
  • Flexible sigmoidoscopy
    • Recommended direct visualization test used for the detection of adenomatous polyps & carcinoma
    • Studies have shown that this test helps reduce mortality risk from CRC
    • Advantages: Requires less preparation & no sedation
    • Disadvantage for this procedure includes colonic perforation, bleeding & examination is limited only to the distal colon
  • Carcinoembryonic antigen (CEA)
    • May be considered as a screening tool for colorectal cancer although some medical societies do not recommend this due to its low sensitivity (46%) & specificity (89%)
    • Also used in monitoring of treatment response & cancer recurrence
  • Chromoendoscopy with dye-spraying/image-enhanced endoscopy (IEE)
    • Yields higher results in detecting dysplasia compared with standard white-light endoscopy
    • Use of indigo carmine dye, although more costly, is preferred over methylene blue (as the former does not induce DNA damage)
  • Computed Tomography Colonography (Virtual Colonoscopy/CTC)
    • A non-invasive technique that may be used to detect polyps or carcinomas >10 mm in size
    • Not suitable for detecting lateral spread & polyps measuring <1 cm
    • Advantages: Does not require sedation, is noninvasive & with very low test-related complications
  • Capsule colonoscopy (Pill Cam colon 2)
    • Approved imaging test for screening of proximal colon for individuals at high risk for colorectal cancer who have undergone colonoscopy but were not able to complete the procedure, & have contraindications to colonoscopy, CT colonography, & sedation
    • Advantages: Non-invasive imaging tool with lesser risk for complications compared to colonoscopy
    • Disadvantages: Needed bowel preparations are more extensive compared to colonoscopy
  • Guaiac-based fecal occult blood testing (gFOBT)
    • Shown by several studies to reduce mortality from CRC 
    • A negative result does not ensure that patient is free from colorectal cancer
    • Disadvantages: Possibility to miss tumors that is not bleeding or only slightly bleeding & high false-positive rates due to reaction from non-heme in food or blood in the upper gastrointestinal tract
  • Fecal immunochemical testing (FIT)
    • Has higher detection rates for advanced adenomas & cancer compared to gFOBT
    • No diet restriction necessary for the test & a single test is sufficient
  • Fecal immunochemical testing-Deoxyribonucleic Acid (FIT-DNA)
    • An emerging screening test that uses FIT to detect DNA biomarkers in stool samples
    • Recommended screening test for average-risk individuals because of its high sensitivity compared to FIT
  • Blood-based screening test
    • Septin 9 (SEPT9) DNA methylated blood test is another new modality used for CRC screening
    • Circulating methylated SEPT9 DNA in plasma is a biomarker for minimally invasive CRC
    • Alternative test for individuals refusing to undergo other screening procedures
    • Disdavantage: Sensitivity in detecting CRC & advanced adenomas is low compared to other screening modalities

Screening based on Risk Stratification

  • Individuals at average risk
    • Recommended at age ≥50 years (≥45 years of age for African Americans or American Indians)
    • Colonoscopy is the preferred screening modality & may be done every 10 years
    • If colonoscopy is incomplete, repeat colonoscopy should be considered or other screening methods (eg double-contrast barium enema) in a shorter interval
    • Other recommended screening tests include annual fecal-based tests (ie gFOBT, FIT, FIT-DNA), flexible sigmoidoscopy every 5 years
  • Individuals at increased risk
    • Following screening colonoscopy & complete polypectomy:
      • Low-risk adenomas (≤2 tubular adenomas measuring <1 cm): 1st follow-up colonoscopy within 5 years, if normal, repeat every 5-10 years
      • Advanced/multiple adenomas (3-10 polyps measuring ≥10 mm & with any villous features or high-grade dysplasia): Repeat colonoscopy within 3 years; subsequent colonoscopies within 5 years, or depending on findings
      • Polypectomy of large sessile polyps (associated with high rate of recurrence): Follow-up colonoscopy within 2-6 months

Screening for Special Population

  • Obese people
    • Screening should be initiated as early as 45 years of age
  • Smokers
    • Based on various studies, screening is recommended among active smokers & those with >20 pack-years of smoking
    • Screen as early as 45 years of age, esp for those with >20 pack-years of smoking

Screening for Patients with Inflammatory Bowel Disease

  • Colonoscopy should be done in all ulcerative colitis & Crohn’s colitis patients every 1-2 years & should be started 8-10 years after onset of symptoms or when in remission
  • Strictures (esp in ulcerative colitis) should be assessed thoroughly through biopsy & brush cytology
  • When deemed appropriate, endoscopic polypectomy with biopsies of surrounding mucosa are done to check for dysplasia

Screening for Patients with Personal History of Colorectal Cancer

  • Colonoscopy 1 year post-operatively (within 3-6 months if preoperative colonoscopy is incomplete)
    • If normal, this is repeated in 2-3 years then every 5 years
    • If sessile serrated polyps (SSP) or adenomas are found, colonoscopy is done in 1-3 years
    • Subsequent colonoscopic intervals will vary among patients but should not exceed 5 years
  • For patients with rectal cancer treated with transanal local excision, proctoscopy with endorectal ultrasound (EUS) or MRI of the rectal anastomosis should be done
    • Repeat every 3-6 months for the 1st 2 years, then every 6 months until 5 years

Screening for Individuals with Positive Family History of Colorectal Cancer

  • Individuals with 1st-degree relative (FDR) with colorectal cancer at any age
    • Colonoscopy beginning 10 years before the earliest diagnosis in the family or at age 40 & repeated every 5-10 years; if positive, may repeat according to colonoscopy results
  • Individuals with at least one 2nd-degree relative with colorectal cancer diagnosed at <50 years
    • Colonoscopy beginning at age 50 & repeated every 5-10 years or according to findings
  • Individuals with 1st-degree relative (FDR) with advanced adenomas
    • Colonoscopy beginning at relative’s age of onset of adenoma or at age 40 years & repeated every 5-10 years or according to findings

Screening for Patients After Surgical/Endoscopic Removal of Adenomatous Polyps

  • Risk of colorectal cancer is increased in patients with ≥3 adenomas measuring >1 cm at 1st colonoscopy or those with villous or high-grade dysplastic component
  • Low-risk patients are those with 1 or 2 adenomas <1 cm without villous or high-grade dysplastic features & may not require colonoscopic surveillance
    • However, colonoscopy may be performed at 5 years if other factors are present (eg family history)
  • Patients with either one adenoma measuring >1 cm in size or 3-4 small adenomas <1 cm are considered intermediate risk & surveillance colonoscopy is recommended every 3 years
  • Presence of ≥5 small adenomas or ≥3 adenomas, with at least one measuring ≥1 cm in size, patient is high risk & should have colonoscopy yearly
  • Surveillance colonoscopy is recommended for adults age 50-75 years 
  • Surveillance colonoscopy is not recommended to continue beyond 75 years of age


Colorectal Cancer Prevention


  • Regarded as the most important acquired factor in colorectal cancer
  • Diets rich in fiber may help reduce the risk for colorectal cancer
  • Calcium salts & calcium-rich foods may have protective role in colorectal cancer since they decrease colon cell turnover & reduce the cancer-promoting effects of fatty acids & bile acids
  • Consumption of red meat should be limited to <500 g (18 oz) per week but processed food should be avoided

Weight management

  • Maintain body mass index (BMI) near the lower limit of the normal range

Physical Activity

  • Adults should aim to have at least 2.5 hours of moderate intensity exercise (eg brisk walking) a week or 30 minutes on at least 5 days a week


  • Should be limited to no more than 2 drinks per day (30 g of ethanol or 4 units) for men & one drink per day (15 g of ethanol or 2 units) for women


  • Patients should be discouraged from smoking or, for smokers, encouraged to quit smoking

Follow Up

  • Detecting relapse in advance is the main goal
    • Rise in carcinoembryonic antigen level is usually the first signal of recurrence & is most effective in patients with elevation preoperatively
  • Colorectal cancer surveillance include:
    • History, physical examination every 3-6 months for 2 years, then every 6 months for a total of 5 years
    • CEA test at baseline, then every 3-6 months for 2 years, then every 6 months for a total of 5 years if cancer is potentially resectable for isolated metastases
    • Colonoscopy at 1 year post-resection or every 3-6 months after resection if not done preoperatively due to an obstructing lesion; repeat at 3 years, then every 5 years thereafter
      • If follow-up colonoscopy reveals advanced adenoma, repeat colonoscopy in 1 year
      • More frequently done if colorectal cancer presented before 50 years of age
      • Important also in identifying & removing metachronous polyps, especially in the first 2 years after resection
    • CT scan of the chest, abdomen & pelvis yearly for 5 years among stage II & III patients
      •  Consider every 6-12 months for the first 3 years in patients who are at higher risk of recurrence
      •  Important in monitoring potentially resectable metastases
    •  Endoscopic surveillance for patients who underwent endoscopic removal of polyps with invasive cancer should be individualized
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