HMN 2025: What is the Hidden bowel cancer risk in common growths

Flinders University and Flinders Medical Center researchers have found a critical link between having two types of polyps, common growths found in the bowel, and an increased risk of developing cancer, according to a new study published in Clinical Gastroenterology and Hepatology (CGH) titled “Risk of advanced colorectal neoplasia at follow-up colonoscopy after synchronous adenoma and clinically significant serrated polyp.”

Bowel, or colorectal, cancer is the second deadliest and fourth most common type of newly diagnosed cancer in Australia.

Most bowel cancers start as benign polyps, non-threatening growths, on the wall or lining of the bowel, however there are two types—adenomas and serrated polyps—that can develop into cancer.

The new study analyzed over 8,400 colonoscopy records and found that people with both adenomas and serrated polyps were up to five times more likely to develop advanced pre-cancerous changes than those with just one type.

“Polyps are common and usually harmless, but when both types appear together—what we call synchronous lesions—the risk of serious bowel disease or cancer rises sharply,” says Dr. Molla Wassie, lead author and researcher at the FHMRI Bowel Health Service.

Even more concerning, nearly half of all patients with serrated polyps also had adenomas, suggesting this high-risk group is more widespread than previously thought.

“This is one of the largest studies of its kind,” says Dr. Wassie.

“Our findings support growing international evidence that these two types of polyps may represent separate cancer pathways that can be active at the same time—making early detection and regular monitoring even more important.”

The study also found that serrated polyps may progress to cancer faster than adenomas, reinforcing the need for tailored colonoscopy surveillance guidelines.

“Polyps become more common as we age, but the key is catching and removing them early,” says Dr. Wassie.

“If you’ve had both types of polyps, it’s especially important to stay on top of your colonoscopy schedule.”