Written and peer-reviewed by physicians—but use at your own risk. Read our disclaimer.

banner image


Trusted medical answers—in seconds.

Get access to 1,000+ medical articles with instant search
and clinical tools.

Try free for 5 days

Colorectal cancer

Last updated: January 27, 2021

Summarytoggle arrow icon

Colorectal cancer (CRC) is the fourth most commonly diagnosed cancer the United States. Risk factors include a positive family history, hereditary syndromes, diet, and a number of conditions, such as inflammatory bowel disease. Most colorectal cancers are adenocarcinomas (95%). Clinical signs are often nonspecific and may include a change in bowel habits, rectal bleeding, and weight loss. Iron deficiency anemia in men > 50 years and postmenopausal women should be considered a warning sign for CRC. Since the introduction of screening with colonoscopy or sigmoidoscopy and fecal occult blood testing, early stage carcinomas have become easier to diagnose in asymptomatic patients. Complete colonoscopy with histopathologic analysis confirms the diagnosis. Staging of the cancer is necessary to evaluate the extent of the disease and determine the appropriate treatment. Curative surgical resection of colorectal cancers and metastases is the preferred method of treatment. Colon cancers are resected via hemicolectomy, while rectal cancers are preferably resected via low anterior resection with total mesorectal excision. Resection is complemented by adjuvant chemotherapy for colon cancer, and neoadjuvant and adjuvant chemoradiation for rectal cancer. Regular follow-ups are recommended after surgical resection.

  • Incidence [1][2]
    • Fourth most common cancer in the US overall
    • Accounts for ∼ 8% of all new cancer cases in the US
    • Peak incidence: between 65 and 74 years of age
  • Prevalence: ∼ 0.4%
  • Mortality: second leading cause of cancer-related deaths in the US overall

Epidemiological data refers to the US, unless otherwise specified.

Risk factors for colon cancer [3]

Protective factors [3]

  • Long-term use of aspirin and other NSAIDs
  • Physical activity
  • Diet rich in fiber and vegetables and lower in meat


  • Often times asymptomatic, particularly during the early stages

Constitutional symptoms [6]

Symptoms of right-sided carcinomas [6][7]

Iron deficiency anemia in men > 50 years and postmenopausal women should raise suspicion for colorectal cancer.

Symptoms of left-sided carcinomas [6][7]

  • Definition
  • Symptoms
    • Changes in bowel habits (size, consistency, frequency)
    • Blood-streaked stools
    • Colicky abdominal pain (due to obstruction)
    • Mostly infiltrating mass

Symptoms of rectal carcinomas [6][7]

Colorectal cancer must be ruled out in a patient presenting with rectal bleeding, even if the patient has a history of hemorrhoids.

Symptoms of advanced disease

Symptoms of metastatic disease [8]

The stages of colorectal cancer are based on the TNM staging system by the American Joint Committee for Cancer (AJCC).

Stages of colorectal cancer
AJCC staging (simplified) TNM stage Corresponding Dukes classification stage Description
  • Up to T2, N0, M0
  • A
  • Up to T4, N0, M0
  • B
  • Any T, N1/N2, M0
  • C
  • Any T, any N, M1
  • D

Work-up of colorectal cancer is indicated in symptomatic patients and asymptomatic patients with abnormalities detected during routine screening.

Initial work-up

In up to 5% of cases, multiple adenocarcinomas are present. A complete colonoscopy is necessary to rule out additional tumors.

Staging and further tests

  • Determination of disease extent
  • Treatment monitoring: via carcinoembryonic antigen (CEA)
    • Can not be used for screening
    • Assess serum levels prior to initiating treatment
    • Monitor CEA levels during the course of treatment and the follow-up period to evaluate treatment response and recurrence


95% of all colorectal cancers are adenocarcinomas.

Molecular pathology [10][11]

Small bowel neoplasms

The differential diagnoses listed here are not exhaustive.

Treatment primarily depends on the location of the tumor and the TNM stage. [13]

  • Curative approach
  • Palliative approach
    • Distant metastases beyond the liver and/or lung
    • Patient is not a surgical candidate due to poor general health.
    • Treatment involves palliative chemotherapy and palliative surgery.

Surgical management

Systemic therapy

Radiation therapy is not a standard modality in the treatment of colon cancers.

Surgical management [14]

Transanal excision

  • Indication: early, localized disease (stage I)
  • Procedure: minimally invasive excision of small superficial tumors

Low anterior resection (LAR)

  • Indication: locally advanced disease (stage II–III)
  • Procedure: sphincter-preserving resection of the rectum and sigmoid
    • Total mesorectal excision (TME): en bloc excision of the mesorectum, regional lymph nodes, and vasculature
    • Resection 5 cm beyond the proximal margin of the tumor
    • Resection > 2 cm beyond the distal margin of well-differentiated tumors or > 5 cm beyond the distal margin of poorly differentiated tumors
    • Reconstruction (e.g., side-to-side anastomosis) and optional diverting ostomy
  • Limitations: A minimum distal margin to the tumor is required for reconstruction and preservation of anorectal function.

The completeness of the TME has a strong impact on the prognosis.

Abdominoperineal resection (APR)

Systemic therapy

Screening for colorectal cancer

Screening for colorectal cancer and adenomatous polyps is performed in asymptomatic men and women ≥ 45 years of age.

Low-risk individuals

High-risk individuals

Surveillance [16]

Surveillance following polypectomy
Histology Recommended interval until next control colonoscopy

Hyperplastic polyp

  • 10 years

Low-risk adenoma

  • 5–10 years

High-risk adenoma

  • 3 years

> 10 adenomas

Follow-up [17]

Every patient needs to be monitored for 5 years following the completion of treatment.

  • Patient history, physical examination CEA level
    • Every 3–6 months for 2 years
    • Every 6 months for additional 3 years
  • Chest/abdominal CT: every 6–12 months for 5 years
  • Colonoscopy
    • 1 year after surgical resection
    • 4 years after surgical resection
    • 9 years after surgical resection

85% of recurrences occur within the first three years following treatment.

  1. Key Statistics for Colorectal Cancer. https://www.cancer.org/cancer/colon-rectal-cancer/about/key-statistics.html. Updated: January 5, 2017. Accessed: February 10, 2017.
  2. Cancer Stat Facts: Colorectal Cancer. https://seer.cancer.gov/statfacts/html/colorect.html. . Accessed: November 12, 2020.
  3. Colorectal Cancer Risk Factors. https://www.cancer.org/cancer/colon-rectal-cancer/causes-risks-prevention/risk-factors.html. . Accessed: November 11, 2020.
  4. Xie J, Itzkowitz SH. Cancer in inflammatory bowel disease. World journal of gastroenterology. 2008; 14 (3): p.378-89.
  5. Abdulamir AS, Hafidh RR, Abu bakar F. The association of Streptococcus bovis/gallolyticus with colorectal tumors: the nature and the underlying mechanisms of its etiological role. J Exp Clin Cancer Res. 2011; 30 (1): p.11. doi: 10.1186/1756-9966-30-11 . | Open in Read by QxMD
  6. Colorectal Cancer Signs and Symptoms. https://www.cancer.org/cancer/colon-rectal-cancer/detection-diagnosis-staging/signs-and-symptoms.html. Updated: June 29, 2020. Accessed: November 11, 2020.
  7. Phipps AI, Lindor NM, Jenkins MA, et al. Colon and Rectal Cancer Survival by Tumor Location and Microsatellite Instability. Diseases of the Colon & Rectum. 2013; 56 (8): p.937-944. doi: 10.1097/dcr.0b013e31828f9a57 . | Open in Read by QxMD
  8. Moghadamyeghaneh Z, Alizadeh RF, Phelan M, et al. Trends in colorectal cancer admissions and stage at presentation: impact of screening. Surg Endosc. 2015; 30 (8): p.3604-3610. doi: 10.1007/s00464-015-4662-3 . | Open in Read by QxMD
  9. Apple core sign (colon). https://radiopaedia.org/articles/apple-core-sign-colon-1. Updated: February 10, 2017. Accessed: February 10, 2017.
  10. Adenoma-carcinoma sequence. https://radiopaedia.org/articles/adenoma-carcinoma-sequence-2. Updated: February 10, 2017. Accessed: February 10, 2017.
  11. Colorectal carcinoma. https://radiopaedia.org/articles/colorectal-carcinoma. Updated: February 10, 2017. Accessed: February 10, 2017.
  12. Cancer Stat Facts: Small Intestine Cancer. https://seer.cancer.gov/statfacts/html/smint.html. . Accessed: November 12, 2020.
  13. Colon Cancer Treatment (PDQ®). https://www.cancer.gov/types/colorectal/hp/colon-treatment-pdq. Updated: August 18, 2017. Accessed: January 7, 2018.
  14. Bibbins-Domingo K, Grossman DC, et al. Screening for Colorectal Cancer. JAMA. 2016; 315 (23): p.2564. doi: 10.1001/jama.2016.5989 . | Open in Read by QxMD
  15. Lieberman DA, Rex DK, Winawer SJ, Giardiello FM, Johnson DA, Levin TR. Guidelines for colonoscopy surveillance after screening and polypectomy: A consensus update by the US Multi-Society Task Force on colorectal cancer. Gastroenterology. 2012; 143 (3): p.844-857. doi: 10.1053/j.gastro.2012.06.001 . | Open in Read by QxMD
  16. Living as a Colorectal Cancer Survivor. https://www.cancer.org/cancer/colon-rectal-cancer/after-treatment/living.html. Updated: June 29, 2020. Accessed: November 12, 2020.
  17. Rectal Cancer Treatment (PDQ®)–Health Professional Version. https://www.cancer.gov/types/colorectal/hp/rectal-treatment-pdq. Updated: April 27, 2017. Accessed: January 7, 2018.