Colorectal cancer is a preventable disease but is still the second most common cause of cancer deaths in the United States. Thanks to screening tests such as colonoscopy that can identify and remove polyps (growths on the colon’s lining, some of which can become cancerous over time), this doesn’t have to be the case. Colorectal cancer screening helps people stay healthy—and saves lives.
“The whole idea behind colonoscopy is to interrupt the polyp-to-cancer sequence,” says Lynn F. Butterly, MD, Gastroenterology and Hepatology, Dartmouth Health. “In other words, if you have a polyp, over 10 to 15 years it might develop into colorectal cancer. We're trying to interrupt that process by finding the polyp before it has a chance to become a cancer—and removing it.”
Screening test options
For individuals who are at average risk for colorectal cancer, there are several ways to screen for it, including at-home test kits that can be mailed back to a lab or provider’s office. These stool tests include fecal occult blood tests (FOBTs, such as FIT) and multi-target stool DNA (Cologuard). Fecal occult blood tests look for and identify blood hidden in stool. If the test shows a positive result, a colonoscopy is necessary to complete the screening and make sure there are no growths in the colon that caused the test to be positive. If the FOBT result is negative, it should be retaken in 1 year.
Cologuard is an at-home stool DNA test that’s more sensitive than FOBTs and can identify precancerous polyps and colorectal cancer more frequently, according to a large comparison study. While more expensive than FIT, Cologuard is covered by most insurances and doesn’t need to be repeated for 3 years if results are negative.
Colonoscopies are procedures that allow for polyps to be identified and painlessly removed during the tests. This prevents a polyp from being able to develop into cancer. If cancer is already present, finding it early allows for better treatment outcomes. At least 40% of patients are found to have polyps.
When to screen
In 2018, the American Cancer Society changed its recommendation to start colorectal screenings earlier: at age 45 instead of 50 for people at average risk. Data from the New Hampshire Colonoscopy Registry supports this recommendation. If results are normal and the patient is at average risk, the test is repeated in 10 years. When polyps are found, or if there is a significant family history of colorectal cancer or polyps, a colonoscopy is repeated sooner depending on the patient’s individual results and risk factors.
People with a family history of parents, siblings or children having potentially pre-cancerous polyps or colorectal cancer are at an increased risk for polyps or cancer. They should be screened by colonoscopy starting at age 40 (instead of age 45), or 10 years earlier than the family member’s age at diagnosis of colorectal cancer—whichever comes first. For example, if a patient’s mother was diagnosed with colorectal cancer at 45, the patient should have a colonoscopy at age 35.
Treatments today and looking ahead
Most people with colorectal cancer are diagnosed from biopsies resulting from a colonoscopy. There are three main treatment approaches to colorectal cancer: surgery, chemotherapy and radiation. Gabriel Brooks, MD, Medical Oncology, Dartmouth Cancer Center, explains that for patients with stage 1 or average risk stage 2 colon cancer, surgery is usually the only required treatment. Stage 3 colon cancer or higher risk stage 2 patients typically have surgery followed by chemotherapy to reduce the chance of cancer returning. Radiation is used mostly for the treatment of rectal cancer, often as the first treatment.
The Cancer Center is working on various clinical trials for determining the best treatment for different types and stages of colorectal cancer. Two of these trials focus on immunotherapy and new technology that monitors DNA circulating in the blood, called circulating tumor DNA.
“Colon cancer and rectal cancer are, in many cases, treatable, but they are also preventable,” Brooks says. “Even though screening may seem like a mild inconvenience, believe me, cancer treatment is a greater inconvenience.”
To learn more about colorectal cancer screening and treatment, view a recent
Dartmouth Health webinar featuring Butterly and Brooks here.