Risk of progression of advanced adenomas to colorectal cancer by age and sex: estimates based on 840,149 screening colonoscopies

Objectives

To derive age and sex specific estimates of transition rates from advanced adenomas to colorectal cancer by combining data of a nationwide screening colonoscopy registry and national data on colorectal cancer (CRC) incidence.

Design

Registry based study.

Setting

National screening colonoscopy programme in Germany.

Patients

Participants of screening colonoscopy in 2003 and 2004 (n?=?840?149).

Main outcome measures

Advanced adenoma prevalence, colorectal cancer incidence, annual and 10 year cumulative risk of developing CRC among carriers of advanced adenomas according to sex and age (range 55–80+ years)

Results

The age gradient is much stronger for CRC incidence than for advanced adenoma prevalence. As a result, projected annual transition rates from advanced adenomas to CRC strongly increase with age (from 2.6% in age group 55–59 years to 5.6% in age group ?80 years among women, and from 2.6% in age group 55–59 years to 5.1% in age group ?80 years among men). Projections of 10 year cumulative risk increase from 25.4% at age 55 years to 42.9% at age 80 years in women, and from 25.2% at age 55 years to 39.7% at age 80 years in men.

Conclusions

Advanced adenoma transition rates are similar in both sexes, but there is a strong age gradient for both sexes. Our estimates of transition rates in older age groups are in line with previous estimates derived from small case series in the pre‐colonoscopy era independent of age. However, our projections for younger age groups are considerably lower. These findings may have important implications for the design of CRC screening programmes.Most colorectal cancers (CRCs) develop from adenomas, among which “advanced” adenomas are considered to be the clinically relevant precursors of CRC. The natural history of colorectal adenomas is a decisive factor for the design of CRC screening measures and their cost effectiveness. Since advanced adenomas need to be removed once they are detected, any direct observation of their natural history would be unethical. Thus, available estimates for the progression of adenomas mostly stem from radiological surveillance data or from autopsy series collected prior to the colonoscopy era.^{1,2,3,4,5,6,7,8,9} However, these data are rather vague as they were derived from small and potentially selective samples. For example, a major source for the estimation of adenoma transition rates has been a retrospective review of Mayo Clinic records from 226 patients with colonic polyps ?10?mm in diameter in whom periodic radiographical examination of the colon was performed, and in whom 21 invasive carcinomas were identified during a mean follow up of 9 years.⁹ Despite the undoubted usefulness of available data sources from the pre‐colonoscopy era, sample size limitations did not allow reliable estimates of adenoma transition rates according to key factors, such as age and sex. Accordingly, a common estimate of these transition rates for all ages and both sexes has generally been assumed in previous studies on effectiveness and cost effectiveness of CRC screening.^{10,11,12,13,14,15,16,17} Given that sensitivity analyses in these studies showed that the advanced adenoma–carcinoma transition rate represents a very influential parameter,^10,11,13,18 its variation by age and sex might have a large impact on relative effectiveness and cost effectiveness of various screening schemes.The aim of this paper was to estimate risk for developing CRC according to age and sex among carriers of advanced adenomas by combining data from a large national colonoscopy screening database and national data on CRC incidence in Germany.