Colorectal cancer (CRC) is the second leading cause of cancer related deaths in the United States. Nearly 137,000 people in the US are diagnosed with colon cancer every year and over 50,000 people die of colon cancer every year. CRC can largely be prevented with screening and the early detection and removal of polyps. In addition, the five year survival for patients with CRC is over 90% when the cancer is discovered at an early stage.
Colon and Rectal Invasive Cancer Incidence per 100,000 by age band:
Colon Cancer Incidence NYS: 2008-2012
Overall incidence (lifetime risk) is 1:17 for men and 1:18 for women
The US Preventive Services Task Force recommends screening for colon cancer beginning at age 50 and continuing until 75 years of age for average risk patients. Most of us are average risk and family history will tell us who we should screen earlier. A single first-degree relative with CRC or an advanced adenoma before age 60 has increased risk. A person with two first degree relatives with CRC or advanced adenoma at any age is at higher risk. Higher risk persons should have colonoscopy every 5 years beginning at age 40 or 10 years younger than the age at diagnosis of the youngest relative. African Americans should begin screening at age 45 due to a higher incidence of CRC in this population. There is some question about earlier screening of heavy smokers and medically significant obesity, but this is not included in the recommendations at this time.
Who is high risk?
- One first degree relative with cancer or advanced adenoma before age 60
- Two or more first degree relatives with colorectal cancer at any age
- African Americans (begin screening at age 45)
Colorectal Cancer Incidence by Race/Ethnicity:
SEER 18 2008-2012
Recommendations for average risk patients:
U.S.Preventive Services Task Force recommends high sensitivity fecal occult blood testing (FOBT) every year, flexible sigmoidoscopy (FSIG) every 5 years along with FOBT every 3 years, or colonoscopy every 10 years. They do not recommend routine screening for adults over age 75 although there may be patients between 75 and 85 for whom screening may be supported on an individual basis.
The American Cancer Society has a much longer list of screening tools that includes FSIG every 5 years, colonoscopy every 10 years, double contrast barium enema every 5 years, CT colonoscopy every 5 years, guaiac based FOBT every years or stool DNA testing every 3 years.
The American College of Gastroenterology prefers colonoscopy every 10 years beginning at age 50 (age 45 for African Americans) as a “cancer prevention” test and an annual fecal immunochemical test (FIT) for those who decline colonoscopy as a “cancer detection” test.
Comparing the screening tests:
Stool cancer detection tests: Guaiac based FOBT has largely been supplanted by FIT, which uses antibodies to detect human hemoglobin specifically. Dietary restrictions are not necessary and annual testing has been shown to reduce deaths due to CRC by 15 to 30%. The DNA stool tests for CRC detect blood and nine DNA biomarkers for CRC and adenomas, but the test is expensive. The DNA test does find more lesions than FIT, but it also has a much higher false positive rate.
Radiologic tests: CT colonography (virtual colonoscopy) requires the same prep as colonoscopy and any lesions or potential lesions will still require colonoscopy for evaluation. Medicare and many insurance companies do not cover CT colonography. Double contrast barium enema is less sensitive than colonoscopy for detecting polyps or cancer and also has a fairly high radiation exposure risk.
Endoscopy: FSIG is an endoscope to examine the lowest 60 cm of the colon and rectum. Although it has been shown to substantially reduce CRC incidence and mortality, it has fallen out of favor in most practices with the improved access to colonoscopy.
Colonoscopy is preferred by the ACG because it sees the whole colon, but it does have risk. There is a perforation rate of 1-3 per 1000, significant bleeding in 1-6 per 1000 and transient bacteremia is seen in about 4% of procedures. A 2010 review showed the mortality from colonoscopy procedures to be 0.03%. Overall complication rate is 7 per 1000 (less than 1%).
Making a choice:
So how do we make sense of so many recommendations for screening our average risk patients, particularly in rural areas and in health centers with limited access to colonoscopy? First of all, FIT is a good screening test; it is low risk and has been shown to decrease mortality. Colonoscopy is a great test, but it is limited by access to gastroenterologists and surgery centers. Considering that the incidence of colon cancer merges with the risk of colonoscopy around age 65, it is a cost effective and very reasonable option to perform FIT annually from age 50 to 65, then to have a colonoscopy at age 65.
Average risk patients:
- FIT every year beginning at age 50
- Colonoscopy every 10 years
- FIT every year from 50 to 65, then colonoscopy at age 65