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  • Growth rates and histopathological outcomes of small (6–9 mm) colorectal polyps based on CT colonography surveillance and endoscopic removal

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Original research
Growth rates and histopathological outcomes of small (6–9 mm) colorectal polyps based on CT colonography surveillance and endoscopic removal
  1. B Dustin Pooler1,
  2. David H Kim1,
  3. Kristina A Matkowskyj2,3,
  4. Michael A Newton4,5,
  5. Richard B Halberg6,7,
  6. William M Grady8,9,
  7. Cesare Hassan10,11,
  8. Perry J Pickhardt1
  1. 1 Department of Radiology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA
  2. 2 Department of Pathology and Laboratory Medicine, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA
  3. 3 William S Middleton Memorial Veterans Hospital and Clinics, Madison, Wisconsin, USA
  4. 4 Department of Biostatistics and Medical Informatics, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA
  5. 5 Department of Statistics, College of Letters and Science, University of Wisconsin-Madison, Madison, Wisconsin, USA
  6. 6 Department of Medicine, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA
  7. 7 Department of Oncology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA
  8. 8 Department of Medicine, Division of Gastroentrology, University of Washington School of Medicine, Seattle, Washington, USA
  9. 9 Division of Translational Science and Therapeutics, Fred Hutchinson Cancer Center, Seattle, Washington, USA
  10. 10 Department of Biomedical Sciences, Humanitas University, Milan, Italy
  11. 11 Endoscopy Unit, IRCCS Humanitas Research Hospital, Milan, Italy
  1. Correspondence to Dr Perry J Pickhardt, University of Wisconsin-Madison, Madison, WI 53792-3252, USA; ppickhardt2{at}uwhealth.org

Abstract

Background and aims The natural history of small polyps is not well established and rests on limited evidence from barium enema studies decades ago. Patients with one or two small polyps (6–9 mm) at screening CT colonography (CTC) are offered CTC surveillance at 3 years but may elect immediate colonoscopy. This practice allows direct observation of the growth of subcentimetre polyps, with histopathological correlation in patients undergoing subsequent polypectomy.

Design Of 11 165 asymptomatic patients screened by CTC over a period of 16.4 years, 1067 had one or two 6–9 mm polyps detected (with no polyps ≥10 mm). Of these, 314 (mean age, 57.4 years; M:F, 141:173; 375 total polyps) elected immediate colonoscopic polypectomy, and 382 (mean age 57.0 years; M:F, 217:165; 481 total polyps) elected CTC surveillance over a mean of 4.7 years. Volumetric polyp growth was analysed, with histopathological correlation for resected polyps. Polyp growth and regression were defined as volume change of ±20% per year, with rapid growth defined as +100% per year (annual volume doubling). Regression analysis was performed to evaluate predictors of advanced histology, defined as the presence of cancer, high-grade dysplasia (HGD) or villous components.

Results Of the 314 patients who underwent immediate polypectomy, 67.8% (213/314) harboured adenomas, 2.2% (7/314) with advanced histology; no polyps contained cancer or HGD. Of 382 patients who underwent CTC surveillance, 24.9% (95/382) had polyps that grew, while 62.0% (237/382) remained stable and 13.1% (50/382) regressed in size. Of the 58.6% (224/382) CTC surveillance patients who ultimately underwent colonoscopic resection, 87.1% (195/224) harboured adenomas, 12.9% (29/224) with advanced histology. Of CTC surveillance patients with growing polyps who underwent resection, 23.2% (19/82) harboured advanced histology vs 7.0% (10/142) with stable or regressing polyps (OR: 4.0; p<0.001), with even greater risk of advanced histology in those with rapid growth (63.6%, 14/22, OR: 25.4; p<0.001). Polyp growth, but not patient age/sex or polyp morphology/location were significant predictors of advanced histology.

Conclusion Small 6–9 mm polyps present overall low risk to patients, with polyp growth strongly associated with higher risk lesions. Most patients (75%) with small 6–9 mm polyps will see polyp stability or regression, with advanced histology seen in only 7%. The minority of patients (25%) with small polyps that do grow have a 3-fold increased risk of advanced histology.

  • COLONIC POLYPS
  • COLORECTAL CANCER
  • COLORECTAL ADENOMAS
  • COMPUTER TOMOGRAPHY

Data availability statement

Data are available on reasonable request.

https://doi.org/10.1136/gutjnl-2022-326970

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    Data availability statement

    Data are available on reasonable request.

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    Footnotes

    • Contributors All authors participated in and contributed materially to the design of this study, as well as manuscript writing, production, and editing. The decision to publish and final submitted manuscript was approved by all authors. Data collection was conducted principally by PJP, DHK, KAM and BDP. Data and statistical analysis was conducted principally by MAN and BDP. PJP and BDP serve as joint guarantors for the study and accept full responsibility for the finished work.

    • Funding This research was supported in part by the National Institutes of Health NCI grants 1R01 CA144835-01, 1R01 CA169331-01 and 1R01 CA220004-01.

    • Disclaimer There are no competing interests or conflicts of interest for any author. The authors wish to disclose the following non-competing interests: PJP: advisor to Bracco, GE HealthCare and Nanox-AI; DHK: shareholder of Elucent; KAM: interests in Amgen, Astellas Pharma US and Merck; WMG: interests in Guardent Health, SEngine, Freenome, Natera, Diacarta, GLG, Guidepoint and LucidDX. The other authors have no disclosures.

    • Competing interests None declared.

    • Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research.

    • Provenance and peer review Not commissioned; externally peer reviewed.