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Tubular-adenoma-colorectal-cancer

Image: Tubular adenoma 2 intermed mag, by Nephron. License: CC BY-SA 3.0


Introduction

Colorectal cancer (CRC) is a common and serious disease. It has a low incidence before age 40, with the incidence increasing to about 3.7 per 1000 by age 80. Early removal of premalignant adenomas can prevent malignant cancer and CRC-related death.

Modern screening tests can meet this goal as they can detect early-stage adenocarcinomas and adenomatous polyps. Adults over 50 years of age are more likely to have adenomatous polyps which are related to a higher risk of CRC. The survival rates of CRC depend on the following:

  • Diagnosis while it is limited to the bowel walls (90%)
  • Lymph node involvement but no metastasis (68%)
  • Distant metastasis (10%)
Colorectal-Cancer

Image: Colorectal cancer, by Blausen Medical Communications, Inc. License: CC BY 3.0

Epidemiology of Colorectal Cancer

CRC is the second most common cancer in women and the third most common cancer in men, accounting for 9% of cancer deaths overall. About 1 in 3 persons who develop CRC die because of related complications. The lifetime incidence increases from 5% in a patient with low risk to 90% if the disease occurs after the age of 50. Women are at an increased risk of CRC if they have a history of adenomatous polyps. A family history of adenomatous polyps or CRC in one or more first-degree relatives or a history of CRC in two or more second-degree relatives also increases risk.

Women who are at high risk of developing CRC include individuals who have a history of inflammatory bowel diseases, such as chronic ulcerative colitis or Crohn’s disease. The risk is also high if they have a personal or family history of familial adenomatous polyposis (FAP) or hereditary non-polyposis colon cancer (HNPCC or Lynch syndrome). Women with HNPCC are also at risk for endometrial, ovarian, and other related cancers.

Lifestyle factors associated with CRC:

  • Smoking
  • Lack of physical activity and regular exercise
  • Alcohol intake
  • Red and processed meats
  • Obesity

When to screen for CRC

The screening for CRC should start at age 50 or at age 45 in African Americans. The US Preventive Services Task Force (USPSTF) recommends that screening should continue until age 75. To screen or not to screen becomes an individualized decision after the age of 75. The decision is based on the overall health of the patient prior to screening.

Two types of screening

  • Tests for cancer prevention
  • Tests for cancer detection

Cancer prevention tests are preferred over cancer detection tests.

Screening Tests

Three categories of individuals could substantially benefit from screening tests:

  • Adults with no past screening history
  • Individuals who are capable of receiving cancer treatment if diagnosed with CRC
  • Individuals who are free of life-limiting conditions

American Academy of Family Physicians (AAFP) recommendations:

The AAFP suggests screening for colorectal cancerous growth at age 50. The screening should continue up to age 75. The proposed tests for screening purposes are fecal immunochemical tests (FITs), flexible sigmoidoscopy, and colonoscopy.

The various screening techniques differ with regard to their advantages and disadvantages, and the importance of their findings.

The decision for screening in the age group 76–85 years is an individual one. The general health of the patient and past screening history should be considered before settling on a screening choice.

The AAFP does not recommend screening for CRC in adults after the age of 85.

U.S. Preventive Services Task Force (USPSTF) recommendations:

USPSTF recommendations for colorectal disease screening are the ones given by the AAFP. The guidelines also include screening tests for CRC.

Stool-based screening tests are performed at various intervals. A guaiac-based fecal occult blood test is used for screening purposes at an interval of 1 year. The FIT is repeated every year. A multitarget stool DNA test with a FIT is recommended every 1–3 years.

The direct visualization screening tests involve colonoscopy, which is recommended every 10 years for screening purposes. CT colonography and flexible sigmoidoscopy are repeated every 5 years. Flexible sigmoidoscopy with FIT is recommended, repeating flexible sigmoidoscopy every 10 years and FIT every year.

American College of Gastroenterology (ACG) recommendations:

The ACG recommendations differentiate between screening tests and identification tests for CRC. Specific ACG guidelines include:

  • Tests used for cancer prevention are preferred over diagnostic tests
  • Screening tests should start at age 50 or at age 45 in the case of African Americans. The preferred test is colonoscopy at an interval of 10 years.
  • If the patient refuses colonoscopy and other screening tests, a yearly FIT should be suggested.

According to ACG recommendations, two classes of individuals should undergo a colonoscopy starting at age 40, with a repeat every 5 years:

  1. People who have at least one first-degree relative with a history of advanced adenoma or CRC diagnosis before age 60.
  2. Individuals who have two first-degree relatives diagnosed with advanced adenoma or CRC.

Intervals for follow-up colonoscopy:

  • Cases of villous adenoma and high-grade dysplasia should undergo a follow-up every 3 years.
  • Dysplasia in a sessile serrated polyp should be followed up every 3 years.
  • Large serrated adenoma should undergo follow-up colonoscopy every 5–10 years.
  • Individuals with more than 10 adenomas should have a colonoscopy every 3 years.
  • After resection of a large adenoma, follow-up is recommended within less than a year.
  • In status post-curative resection of large CRC, follow-up should be 3–5 years after the resection.
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