Colorectal cancer screening: Clinical sciences

Colorectal cancer screening is an important and effective tool aimed to identify populations who are at risk for developing colorectal cancer and to detect precancerous lesions early. Over the last few decades, early screening has become even more critical as the incidence of colorectal cancer has increased for patients between the ages of 40 and 54 years. The risk of developing colorectal cancer during one’s lifetime depends on both genetic and environmental factors. So, the initial portion of screening involves identifying these risk factors in order to help us determine which patients need to be screened earlier.

Alright, screening a patient for colorectal cancer starts with assessing for any risk factors that are associated with future development of the cancer. The top five risk factors that puts your patient at high risk include personal or family history of colorectal cancer; hereditary colon cancer syndromes such as familial adenomatous polyposis or FAP, and Lynch syndrome, also known as hereditary non-polyposis colorectal cancer; as well as inflammatory bowel disease or IBD for short, like ulcerative colitis and Crohn disease; abdominopelvic radiation treatments; and cystic fibrosis. If your patient has any of these risk factors, they are considered high risk and will need to be screened for colorectal cancer earlier than the average risk patient, depending on their specific risk factors.

In addition, there are other less significant risk factors that put your patient at average risk for colorectal cancer. These include male sex; race such as Black, Native American, and Alaskan Native; history of transplantation or immunosuppression; obesity; tobacco and alcohol use; a diet high in red or processed meats; and long-term androgen deprivation therapy used for instance in prostate cancer treatment. Although these characteristics can be associated with increased incidence of colorectal cancer, patients with these factors are still considered average risk and screening is recommended to start at 45 years of age.

Alright, let’s talk about screening test options for average risk patients. Patients who are considered to be at average risk have two options for screening tests. The first option is to undergo initial screening colonoscopy starting at age 45. If the exam is normal or only hyperplastic polyps are present, then your patient can follow up with a repeat colonoscopy in 10 years. However, if adenomatous polyps are found, then they would need a repeat colonoscopy earlier depending on the individual characteristics.

This should be done in 5 years for patients with 1 to 2 adenomatous polyps smaller than 1 cm in size, or with low-grade dysplasia on pathology. On the other hand, the patient should return for colonoscopy in 3 years if they have more than 3 polyps larger than 1 cm with high-grade dysplasia or with villous features.

On the other hand, average risk patients can choose alternative methods of testing other than a colonoscopy. These include fecal immunochemical tests and fecal occult blood tests which would need to be performed every year; double-contrast barium enema, and CT colonography performed every 5 years. If the exam is normal, your patient may continue with their screening test of choice every 1 to 5 years as recommended. However, if there are any suspicious or inconclusive findings such as blood in the stool or polyps, then a colonoscopy should be performed as soon as possible.

Okay, now let’s turn our attention to the high risk patients. Remember, the presence of at least one of the following five major risk factors are what categorizes a patient as being at high risk: personal or family history of colorectal cancer, hereditary colon cancer syndromes such as familial adenomatous polyposis, or FAP, and Lynch syndrome, inflammatory bowel disease like ulcerative colitis and Crohn’s disease, abdominopelvic radiation treatments, and cystic fibrosis. These factors contribute to an increased likelihood of developing colorectal cancer through abnormal replication of colorectal mucosal cells, so these patients need screening earlier in life. The timing of the screening depends on which of the risk factors they have.

For instance, if the patient has no family history of hereditary colon cancer syndromes and no personal history of IBD, but they have a family history of colorectal cancer, personal history of abdominal radiation treatment, or cystic fibrosis, you should initiate colonoscopy screening at age 40 or 10 years younger than their first-degree relative’s age at initial diagnosis of colorectal cancer. For instance, if one of the patient’s parents was diagnosed with colorectal cancer at age 40, your patient should undergo their initial screening at age 30.

Now, if the result of the initial colonoscopy is normal or only hyperplastic polyps are found, then the patient can return for a repeat colonoscopy in 5 years. On the other hand, if adenomatous polyps are present, the timing for a repeat colonoscopy will vary depending on the individual characteristics, just as the average risk patients.