- In a prospective follow-up of more than 120,000 individuals, those with advanced adenoma or a large sessile polyp were substantially more likely to develop colorectal cancer (CRC) than those with no polyp
- Large size, multiplicity and villous histology of adenomas all predicted higher CRC risk
- Individuals with non-advanced adenoma or a small sessile polyp were not at increased risk of CRC
Professional society guidelines advise regular colonoscopic surveillance for individuals diagnosed with conventional adenomas or serrated polyps on screening endoscopy. The recommended intervals vary widely, though, and the advice is based largely on weak or modest evidence about the risk of colorectal cancer (CRC) after polypectomy.
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To fill the knowledge gap, Xiosheng He, MD, former postdoctoral researcher at Massachusetts General Hospital, Mingyang Song, MD, ScD, assistant professor in the Department of Medicine, and colleagues prospectively analyzed data on three very large cohorts. Their findings, published in Gastroenterology, provide support for certain current guidelines.
The researchers analyzed data on 122,899 individuals: 106,220 U.S. female registered nurses (43,147 participants in the Nurses' Health Study and 63,073 in the Nurses' Health Study 2) and 16,679 male health care professionals (people in the Health Professionals Follow-up Study).
Participants in these studies complete health questionnaires every two years, and questions about flexible sigmoidoscopy or colonoscopy were added in 1989 (Nurses' Health Study 2) or 1990 (the other two studies). If a participant reported that a colorectal polyp or CRC had been diagnosed at first endoscopy in the past two years, the researchers requested permission to obtain endoscopic and pathologic reports.
Endoscopic findings were categorized as no polyp, conventional adenoma or serrated polyp (hyperplastic polyp, traditional serrated adenoma or sessile serrated adenoma, with or without cytological dysplasia). Follow-up lasted 22 to 24 years, depending on the cohort (median of 10 years).
At the conclusion of their study, researchers documented the following:
Incidence of Conventional Adenoma and CRC Risk
- Any conventional adenoma: Hazard ratio (HR) for CRC of 2.61 compared with participants who had no polyp
- Any advanced adenoma: HR of 4.07
- Non-advanced adenoma: No increased risk of CRC
Influences on CRC Risk with Conventional Adenoma
Type of advanced histology:
- Tubulovillous adenoma: HR of 3.17
- Villous adenoma: HR of 8.51
- High-grade dysplasia: HR of 5.95
- 1–2 small conventional adenomas with villous component: HR of 2.91
- At least one ≥10 mm tubular adenoma: HR of 3.40
- 3–10 tubular adenomas of any size: HR of 3.15
- 1–2 small tubular adenomas: No increased risk of CRC
The sublocation of adenomas did not significantly affect risk.
Serrated Polyps and CRC Risk
- Any serrated polyp: HR of 1.52 (95% CI, 1.00–2.31; P = .05)
- Large serrated polyps: HR of 3.35
- Small serrated polyps: No increased risk of CRC
There was no association between CRC risk and the multiplicity or sublocation of serrated polyps.
Some U.S. and European guidelines advise repeat colonoscopy within three years for patients diagnosed with an advanced adenoma, a large serrated polyp or one to two small villous adenomas. These data support those recommendations.
On the other hand, it seems that patients who have non-advanced adenomas or small serrated polyps don't need more intensive surveillance than individuals in whom no polyp is detected at first endoscopy.
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