Volumetric growth rates of sessile serrated adenomas/polyps observed in situ at longitudinal CT colonography
Sessile serrated adenomas/polyps (SSA/Ps) are now recognized as potential cancer precursors, but little is known about their natural history. We assessed the in vivo growth rates of histologically proven SSA/Ps at longitudinal CT colonography (CTC) and compared results with non-advanced tubular adenomas (TAs).
We identified a cohort of 53 patients (mean age, 54.8 ± 5.5 years; M:F, 26:27) from one center with a total of 58 SSA/Ps followed longitudinally at CTC (mean follow-up interval, 5.3 ± 1.9 years). Initial and final size measurements were determined using dedicated CTC software. Findings were compared with 141 non-advanced TAs followed at CTC (mean, 4.1 ± 2.3 years) in 113 patients (mean age, 56.8 ± 6.9 years).
SSA/Ps were more often flat (62% [36/58] vs. 14% [20/141], p < 0.0001) and right-sided (98% [57/58] vs. 46% [65/141], p < 0.0001) compared with TAs. Initial average diameter was greater for SSA/Ps (9.3 mm vs. 6.3 mm; p < 0.0001). Mean annual volumetric growth was + 12.7%/year for SSA/Ps vs. + 36.4%/year for TAs (p = 0.028). Using a previously defined threshold of + 20% increase in volume/year to define progression, 22% (13/58) of SSA/Ps and 41% (58/141) of TAs progressed (p = 0.014). None of the SSA/Ps had dysplasia or invasive cancer at histopathology.
Sessile serrated adenoma/polyps demonstrate slower growth compared with conventional non-advanced tubular adenomas, despite larger initial linear size. This less aggressive behavior may help explain the more advanced patient age for serrated pathway cancers. Furthermore, these findings could help inform future colonoscopic surveillance strategies, as current guidelines are largely restricted to expert opinion related to the absence of natural history data.
• Sessile serrated adenoma/polyps (SSA/Ps) tend to be flat, right-sided, and demonstrate slower growth compared with conventional non-advanced tubular adenomas.
• This less aggressive behavior of SSA/Ps may help explain the more advanced patient age for serrated pathway cancers.
KeywordsCT colonography Virtual colonoscopy Polyps Natural history
Sessile serrated adenoma/polyp
Traditional serrated adenomas
The authors would like to acknowledge the support of the following personnel: Holly Casson and Laura Misterek in the UW Virtual Colonoscopy Screening Program. We would also like to acknowledge the other radiologists and gastroenterologists at the UW involved in our colorectal cancer screening programs.
This work was supported in part by the U.S. NIH NCI grant 1R01 CA220004-01.
Compliance with ethical standards
The scientific guarantor of this publication is Perry J. Pickhardt.
Conflict of interest
The authors of this manuscript declare relationships with the following companies: Dr. Pickhardt is advisor to Bracco; shareholder in SHINE, Elucent, and Cellectar.
Statistics and biometry
One of the authors has significant statistical expertise (BDP). However, no complex statistical methods were necessary for this paper.
Written informed consent was obtained from all subjects (patients) in this retrospective study by the Institutional Review Board.
Institutional Review Board approval was obtained.
Study subjects or cohorts overlap
Some study subjects or cohorts have been previously reported in Kim DH, Matkowskyj KA, Lubner MG, Hinshaw JL, Muñoz del Rio A, Pooler BD, Weiss JM, Pickhardt PJ. Serrated polyps at CT colonography: prevalence and characteristics of the serrated polyp spectrum. Radiology 2016;280:455–463. However, that study was simply cross-sectional and did not assess longitudinal changes over time.
• Performed at one institution
- 23.Kim DH, Hinshaw JL, Lubner MG, Munoz del Rio A, Pooler BD, Pickhardt PJ (2014) Contrast coating for the surface of flat polyps at CT colonography: a marker for detection. Eur Radiol 24:940–946. https://doi.org/10.1007/s00330-014-3095-z