In response to a rising incidence in colorectal cancer among young and middle-aged people, the American Cancer Society updated guidelines on Wednesday to recommend screenings begin at age 45, five years earlier than the previous 50 guideline.

The recommendation says that people age 45 to 75 with average risk for colon cancer get regular screenings with a stool test, colonoscopy or other imaging test.

The United States Preventive Services Task Force, an independent volunteer panel supported by the Department of Health and Human Services, however, continues to recommend that screening begin at age 50.

The Cancer Society change is a welcome development, said Dr. Sam Mikhail of the Mark H. Zangmeister Cancer Center in Columbus.

“It’s an important step in the right direction,” he said. “We are seeing a trend where more young people are diagnosed with colon cancer than two or three or four decades ago.”

Colorectal cancer is the second-leading cause of cancer deaths in the United States, killing about 50,000 people each year. Since 1994, there has been a 51 percent increase in colorectal cancer among people ages 20 to 49, according to data collected by the National Cancer Institute.

A 2014 study by researchers at the University of Texas MD Anderson Cancer Center projected that, from 2010 to 2030, colon cancer would increase by 90 percent among patients ages 20 to 34, and by 28 percent among patients 35 to 49. For rectal and related cancers, the expected increases were 124 percent for the younger age group and 46 percent for the older group.

Because most data on screening benefits include only people older than 50, the Cancer Society designates the new guideline as a “qualified” recommendation. That’s weaker than the “strong” recommendation it continues to make for those 50 and up.

Mikhail said more research needs to be focused on younger people to determine whether even lower screening ages would be beneficial.

Dr. Darrell Gray, medical director of endoscopy and gastroenterology services at Ohio State University Hospital East, sees people as young as 20 receiving devastating colorectal cancer diagnoses. Still, he viewed the new recommendation with caution.

“There’s part of me that is excited to see this recommendation,” he said. “At the same time I must temper my excitement with the evidence, and right now we still have limited evidence on the effectiveness of cancer screening among adults less than 50. … It’s hard to say at this point that the potential benefit outweighs the harm.”

That harm, he said, is a negligible risk that colonoscopy could cause a bowel perforation or lead to a complication from sedation.

Mikhail and Gray were among several speakers seeking to raise awareness among health care providers at an April event held in Columbus called “A Call to Action: Colorectal Cancer in the Young — an Alarming Trend.”

At the event, Kim Newcomer of the Washington-based Colorectal Cancer Alliance presented results of a survey that showed that 73 percent of young patients were diagnosed at an advanced stage, when treatment options are limited.

Mikhail said on Wednesday that late diagnoses could occur in part because many doctors think of cancer as a disease of older people. And they don’t consider colon cancer when a young patient has symptoms, such as abdominal discomfort, a change in bowel habits, rectal bleeding or unexplained anemia, he said.