Patients who have had a screening colonoscopy had a steadily increasing predominance of proximal colorectal cancer (CRC) during a 10-year follow-up, especially among older age groups and women, according to a study in Clinical and Translational Gastroenterology.
The analysis was based on data from the German Pharmacoepidemiological Research Database, which includes claims data from 4 statutory health insurance providers in Germany. Eligible participants were aged 55 years and older and underwent a screening colonoscopy between 2006 and 2017. The participants were grouped into those who had a snare polypectomy (cohort 1) and those without polypectomy (cohort 2).
The investigators assessed the cumulative incidence of total, distal, and proximal CRC in both cohorts stratified by sex and age using Kaplan-Meier analysis and determined CRC detection rate at first repeat colonoscopy according to the time since screening colonoscopy.
A total of 1,095,381 patients had a screening colonoscopy between 2006 and 2017. Of the cohort, 7052 men (1.4%) and 4794 women (0.8%) were diagnosed with a CRC at baseline, of which 26% were in the proximal colon. The proportion of proximal CRCs was higher in older age groups and in women vs men.
Cohort 1 included 193,745 patients (mean age, 65.0 years; women, 42.9%), and cohort 2 included 723,880 participants (mean age, 63.9 years; women, 58.2%). About half of the participants in cohort 1 (46.7%; median follow-up, 64 months) had a repeat colonoscopy during the follow-up vs 22.3% in cohort 2 (median follow-up, 69 months).
In the follow-up, 1481 CRCs occurred in cohort 1 and 2400 occurred in cohort 2. For both cohorts and sexes, the proportion of proximal CRCs occurring within 10 years increased with age at baseline. In women from cohort 1 aged 55 to 64 years at baseline, the proportion of proximal CRCs among all CRCs diagnosed during the follow-up was 56.2%. For women aged 65 to 74 years, the proportion of proximal CRCs was 63.2%, and in those aged at least 75 years, it was 66.7%. For men in cohort 1, the proportions of proximal CRCs were 48.0% in those aged 55 to 64 years, 54.4% in those aged 65 to 74 years, and 57.7% in those aged at least 75 years.
In cohort 2, in women aged 55 to 64 years, 65 to 74 years, and at least 75 years at baseline, the proportions of proximal CRC among all CRCs diagnosed during the follow-up were 53.2%, 58.0%, and 62.2%, respectively. In men in cohort 2, these proportions were 43.8%, 47.3%, and 55.3%, respectively.
The CRC detection rate at the first repeat colonoscopy increased based on the time interval since the screening colonoscopy for participants in cohort 1. The greatest increase occurred after 6 years: 1.7% of participants with a first repeat colonoscopy within 6 to 8 years had a CRC detected at first repeat colonoscopy vs 0.8% of those with a first repeat colonoscopy within 4 to 6 years. This increase was observed in men and women, though the increase was higher in women, in analyses stratified by sex.
For cohort 1, the proportion of CRCs detected at an advanced stage increased according to the time since screening colonoscopy, from about 20% in years 1 to 4 to about 40% after over 6 years. For cohort 2, the proportion of CRCs detected at advanced stages ranged from 35% to 46%.
Study limitations include the lack of information on histology of polyps detected at colonoscopy. In addition, the claims data did not contain direct information on the quality of colonoscopy or completeness of polypectomy, and the data on CRC diagnoses may not be completely accurate.
“Our study among persons with screening colonoscopy at baseline followed over 10 years showed a steadily increasing predominance of proximal CRC during follow-up, and this shift showed distinct patterns by age and sex,” the study authors noted. “Among persons with snare polypectomy at baseline, CRC detection rate at first repeat colonoscopy abruptly increased when the examination was performed more than 6 years after baseline.”
Disclosure: Some of the study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.
Schwarz S, Hornschuch M, Pox C, Haug U. Colorectal cancer after screening colonoscopy: 10-year incidence by site and detection rate at first repeat colonoscopy. Clin Transl Gastroenterol. Published online October 6, 2022. doi: 10.14309/ctg.0000000000000535