FRIDAY, March 2 (HealthDay News) -- Approximately one in three U.S. adults between the ages of 50 and 75 who should be screened for colorectal cancer have not been, according to the American Society for Gastrointestinal Endoscopy.

As National Colorectal Cancer Awareness Month kicks off, the society is reminding older adults about the benefits of a colonoscopy exam to screen for colorectal cancer, which is largely preventable, while offering tips on getting screened.

"Colorectal cancer is one of the most preventable cancers because the majority of colorectal cancers arise from precancerous growths in the colon called polyps, which can be found during a colonoscopy screening exam and removed before they turn into cancer," Dr. Gregory Ginsberg, president of the American Society for Gastrointestinal Endoscopy (ASGE), said in a society news release.

ASGE experts say everyone should be screened starting at age 50, and repeat the screening once a decade thereafter if the initial test results come back normal.

Those with a family history of colorectal cancer should get screened starting at age 40. Other high-risk groups, such as black people and those with inflammatory bowel disease, should discuss getting screened sooner with their doctors.

Before the screening, it is important to follow pre-colonoscopy instructions carefully to ensure the colon is thoroughly cleaned so no polyps or cancers are missed during the procedure, Ginsberg said.

Studies suggest that not following the prescreening guidelines results in more missed polyps.

More information

For more on colonoscopies, visit the American Society for Gastrointestinal Endoscopy.