Predicting the risk of recurrent adenoma and incident colorectal cancer based on findings of the baseline colonoscopy

Abstract

Objectives: The decision tree underlying current practice guidelines for post polypectomy surveillance relies on risk stratification based on predictive attributes gleaned from adenomas removed on screening colonoscopy examination. Our primary aim was to estimate the magnitude of association between baseline adenoma attributes and the risk of adenoma recurrence and invasive colorectal adenocarcinoma (CRC). Our secondary aims were to estimate the adenoma detection rate (ADR) of surveillance compared with screening colonoscopies and describe time trends in preventive colonoscopy utilization.

Methods: We used prospective analyses of retrospectively collected clinical data from electronic health records. A cohort of primary care patients eligible for colorectal cancer screening was assembled encompassing 110,452 subjects, of which 3,300 had adenomas removed on screening examination. Of those patients who had a follow-up surveillance colonoscopy (defined as a patient with a documented adenoma on prior colonoscopy) recorded during the study period, 537 had a recurrent adenoma.

Results: Of those recurrent adenomas, 354 had a high-risk attributes. High-risk attributes were described at >3 adenomas, at least one adenoma >10 mm in size, high-grade dysplasia, or villous features. The risk of developing invasive CRC among post polypectomy patients was significantly higher if the baseline adenomas displayed any of the following attributes: more numerous than 3 (4.3-fold higher risk, 95% confidence interval (CI) low, high 1.4, 12.9), larger than 10 mm in size (5.2-fold higher risk, 95% CI low, high 1.8, 15.1), high-grade dysplasia (13.2-fold risk, 95% CI low, high 2.8, 62.1), or villous features (7.4-fold higher risk, 95% CI low, high 2.5, 21.5). These attributes combined added a net value of 22.8% to the probability of correctly predicting CRC. There was a threefold increase in surveillance utilization relative to screening from 2005 to 2011. The ADR of surveillance (34.1%) was 1.5-fold higher than that of screening (23.1%).

Conclusions: These results emphasize the need to mitigate excessive risk by performing timely surveillance colonoscopies in patients with baseline adenomas displaying high-risk attributes as recommended in practice guidelines.

Figure 1

Colonoscopies according to clinical indication. The clinical indication for each of the 25,635 preventative maintenance colonoscopies was ascertained. The indications were classified into average risk screening, elevated risk screening, and surveillance examinations. Average risk screening was defined as a person who did not have symptoms, or had a family history of colorectal cancer in only one first-degree relative older than 60 years of age. Elevated risk screening was defined as an asymptomatic person who had a family history of one first-degree relative diagnosed with colorectal cancer at age 60 years or younger or who had two first-degree relatives diagnosed with colorectal cancer at any age.

Figure 2

Trends over time in colonoscopy utilization. (a) Key metrics for monitoring colonoscopy utilization by fiscal year quarter. Total colonoscopies represents the number of procedures performed per quarter for all indications and denoted by the red line (number of exams is on the right axis of the graph). The ratio of screening/surveillance examinations performed by quarter is noted by the blue line. The ratio of screening and surveillance colonoscopies performed to the total colonoscopies performed (including for symptoms) is noted by the green line. (b) Percentage of total colonoscopies per fiscal year quarter for indications as noted in the key (signs and symptoms, average risk screening, elevated risk screening, inflammatory bowel disease, and surveillance). Average risk screening was defined as a person who did not have symptoms, or had a family history of colorectal cancer in only 1 first-degree relative older than 60 years of age. Elevated risk screening was defined as an asymptomatic person who had a family history of 1 first-degree relative diagnosed with colorectal cancer at age 60 years or younger or who had 2 first-degree relatives diagnosed with colorectal cancer at any age. Screening examination was defined as a person who had a baseline colonoscopy with pathology dictating a recall colonoscopy.