Histological features of advanced colorectal adenomas detected by endoscopy and fecal immunochemical test

Low Colorectal Cancer Risk After Resection of High-Risk Pedunculated Polyps

BACKGROUND

Post-fecal immunochemical test (FIT) colonoscopy represents a setting with an enriched prevalence of advanced adenomas. Due to an expected higher risk of colorectal cancer (CRC), postpolypectomy surveillance is recommended, generating a substantially increased load on endoscopy services. The aim of our study was to investigate postpolypectomy CRC risk in a screening population of FIT+ subjects after resection of low-risk adenomas (LRAs) or high-risk adenomas (HRAs).

METHODS

We retrieved data from a cohort of patients undergoing postpolypectomy surveillance within a FIT-based CRC screening program in Italy between 2002 and 2017 and followed-up to December 2021. Main outcomes were postpolypectomy CRC incidence and mortality risks according to type of adenoma (LRA/HRA) removed at colonoscopy as well as morphology, size, dysplasia, and location of the index lesion. We adopted as comparators FIT+/colonoscopy-negative and FIT- patients. The absolute risk was calculated as the number of incident CRCs per 100,000 person-years of follow-up. We used Cox multivariable regression models to identify associations between CRC risks and patient- and polyp-related variables.

RESULTS

Overall, we included 87,248 post-FIT+ colonoscopies (133 endoscopists). Of these, 42,899 (49.2%) were negative, 21,650 (24.8%) had an LRA, and 22,709 (26.0%) an HRA. After a median follow-up of 7.25 years, a total of 635 CRCs were observed. For patients with LRAs, CRC incidence (hazard ratio [HR], 1.18; 95% confidence interval [CI], 0.92-1.53) was not increased compared with the FIT+/colonoscopy-negative group, while for HRAs a significant increase in CRC incidence (HR, 1.53; 95% CI, 1.14-2.04) was found. The presence of 1 or more risk factors among proximal location, nonpedunculated morphology, and high-grade dysplasia explained most of this excess CRC risk in the HRA group (HR, 1.85; 95% CI, 1.36-2.52). Patients with only distal pedunculated polyps without high-grade dysplasia, representing 39.2% of HRA, did not have increased risk compared with the FIT- group (HR, 0.87; 95% CI, 0.59-1.28).

CONCLUSIONS

CRC incidence is significantly higher in patients with HRAs diagnosed at colonoscopy. However, such excess risk does not appear to apply to patients with only distal pedunculated polyps without high-grade dysplasia, an observation that could potentially reduce the burden of surveillance in FIT programs.

Higher risk of advanced histology in adenoma less than 10 mm in fecal immunochemical test screening: Implication for management

BACKGROUND AND AIM

Whether diminutive or small adenomas detected by fecal immunochemical tests (FITs) are associated with a higher risk of advanced histology remains unknown. We investigated the prevalence of advanced histology in diminutive and small adenomas detected by FIT and compared with that detected by colonoscopy screening.

METHODS

We prospectively compared 1860 FIT-positive patients (FIT-positive cohort) and 6691 average-risk patients (screening colonoscopy cohort). Both groups underwent colonoscopies and were shown to have neoplastic lesions. The prevalence of advanced histology was determined, as was the associations with size and FIT positivity.

RESULTS

We analyzed 3920 neoplastic lesions from the FIT-positive cohort and 9789 neoplastic lesions from the screening colonoscopy cohort. Eighty (4.3%) diminutive lesions in FIT-positive cohort had advanced histology but without any invasive cancer. Twenty-one patients in the FIT-positive cohort and 49 in the screening colonoscopy cohort with diminutive adenomas displayed advanced histology (3.5% vs 1.2%; adjusted odds ratio [aOR] = 2.99, 95% confidence interval [CI]: 1.77-5.06). Sixteen patients in the FIT-positive cohort (2.7%) with diminutive adenomas might have changed the surveillance interval if a resect-and-discard strategy was applied, with a higher likelihood compared with the screening colonoscopy cohort (aOR = 2.76, 95% CI: 1.53-4.99).

CONCLUSIONS

Fecal immunochemical test screening detected more diminutive and small adenomas with advanced histology compared with colonoscopy screening. Its impact on current management of diminutive polyp is limited.

Analysis of the effectiveness of two noninvasive fecal tests used to screen for colorectal cancer in average-risk adults

OBJECTIVES

Colorectal cancer (CRC) is the second leading cause of cancer-related death in the United States. Although a significant proportion of CRC cases and deaths are preventable by screening, the morbidity and mortality from CRC remains high and is attributed to suboptimal screening rates. Low levels of population CRC screening uptake may be due to reluctance toward invasiveness of some screening tests, embarrassment, exposure to anesthesia, and grueling preparation, especially for the invasive screening tests. Noninvasive tests overcome many of these barriers because they are more convenient and potentially more attractive to patients compared to invasive tests. This study uses Markov cohort simulation model developed with the help of TreeAge pro software to compare two noninvasive fecal CRC screens, fecal immunohistochemical test (FIT) and multitarget stool DNA test (Mt-sDNA) with no screening in order to identify the more effective noninvasive fecal test to screen for colorectal cancer in average-risk adults.

STUDY DESIGN

Simulation study developed with Markov model using TreeAge pro software, which included a hypothetical cohort at the average risk of developing colorectal cancer.

METHODS

Markov model was used to compare population-level CRC-related cases and deaths averted, life-years gained (LYG), and colonoscopies required for two noninvasive CRC screening strategies compared with no screening: annual fecal immunohistochemical testing (FIT) and 3-yearly multitarget stool DNA testing (Mt-sDNA). The model simulated the natural history of the adenoma-carcinoma sequence in average-risk persons starting at age 50 years, and natural history parameters were estimated from the literature and via verification to data on precancerous lesions (i.e. adenomas) and CRC incidence. Screening strategies were then superimposed on the natural history component of the model, allowing for precancerous lesions to be detected and removed, or CRC to be detected and treated at a potentially earlier stage. The sensitivity and specificity for each screen for precancerous lesions and CRC were the performance parameters used to estimate the effectiveness.

RESULTS

Annual FIT was more effective than three yearly Mt-sDNA in reducing CRC cases, averting CRC-related deaths, and increasing the LYG compared to no screening. On average, annual FIT resulted in 3.5 fewer CRC cases, and 2.9 fewer CRC deaths per 1000 persons screened compared to 3-yearly Mt-sDNA. Annual FIT usage resulted in a 0.18 LYG compared to Mt-sDNA, which allowed 0.16 LYG, and an annual FIT screening led to a total of 203 more colonoscopies performed compared to Mt-sDNA. One-way sensitivity analysis conducted over the sensitivity rates of each screen by type of lesion showed that FIT remained the more effective strategy for all ranges of sensitivity. Threshold analysis results identified the lowest FIT sensitivity value at which Mt-sDNA performed better for conventional high-risk adenomas and CRC detection to be 0.16 and 0.052, respectively.

CONCLUSION

Both the noninvasive screens were effective compared to no screening. Additionally, annual FIT as a first step noninvasive screening test for CRC appears to be more effective compared to three-yearly Mt-sDNA.

Fecal Immunochemical Test Detects Sessile Serrated Adenomas and Polyps With a Low Level of Sensitivity

BACKGROUND & AIMS

The serrated pathway is a distinct pathway of colorectal carcinogenesis that has been implicated in development of a substantial proportion of interval colorectal cancers. The fecal immunochemical test (FIT) detects early neoplasms with a higher level of sensitivity than the guaiac test. We investigated the sensitivity of the FIT in detection of sessile serrated adenomas/polyps (SSA/Ps).

METHODS

We performed a prospective study of 6198 asymptomatic subjects (mean age, 59.0 ± 7.0 years) who received concurrent screening colonoscopies and FITs at the Health Management Center of National Taiwan University Hospital from August 2010 through November 2014. The sensitivity of FIT for conventional adenoma, advanced adenoma, and SSA/P at different cutoffs was calculated, and results were compared by using multivariate analysis adjusted for potential confounders.

RESULTS

Prevalence values of SSA/P, adenoma, and advanced adenoma were 1.4%, 20.2%, and 5.5%, respectively. At cutoffs of 10, 15, and 20 μg hemoglobin/g feces, the FIT detected all SSA/Ps with 12.3%, 6.2%, and 6.2% sensitivity, large SSA/Ps with 18.4%, 10.5%, and 10.5% sensitivity, and advanced adenomas with 32.4%, 24.5%, and 20.9% sensitivity, respectively. Multivariate analysis revealed that positive results from the FIT did not differ significantly between individuals with SSA/P and those with non-advanced adenoma or those with negative findings from colonoscopy. Patients with large SSA/Ps were less likely to have positive results from the FIT than patients with advanced adenoma, with odds ratios of 0.44 (95% confidence interval [CI], 0.18-1.05), 0.30 (95% CI, 0.10-0.90), and 0.37 (95% CI, 0.12-1.12) at cutoffs of 10, 15, and 20 μg hemoglobin/g feces, respectively, after adjusting for lesion size, even with synchronous conventional adenoma.

CONCLUSIONS

In a prospective study of 6198 subjects receiving the FIT and colonoscopy, we found that the FIT detected SSA/Ps with significantly lower levels of sensitivity than conventional adenoma. Further studies are needed to determine the effects of these findings on the effectiveness of FIT-based colorectal cancer screening program.

Risk Factors for False Fecal Immunochemical Test Results in Colorectal Cancer Screening

GOALS

We investigated the factors associated with false fecal immunochemical test (FIT) results for advanced colorectal neoplasm (ACRN).

BACKGROUND

Data on whether certain subgroups of patients have an increased risk of inaccurate FIT results are extremely limited.

STUDY

This was a retrospective study conducted in a university hospital in Korea from June 2013 to May 2015. Out of 34,547 participants who had an FIT completed, we analyzed a total of 3990 subjects aged 50 years and above who underwent colonoscopy.

RESULTS

The rates of false-negative and false-positive results were 58.0% and 15.7%, respectively. Elevated fasting blood glucose [adjusted odds ratio (AOR), 0.59; 95% confidence interval (CI), 0.36-0.97], the presence of high-grade dysplasia (AOR, 0.49; 95% CI, 0.25-0.95), 3 or more adenomas (AOR, 0.56; 95% CI, 0.35-0.89), cancer (AOR, 0.20; 95% CI, 0.11-0.38), and distal ACRN (AOR, 0.61; 95% CI, 0.39-0.96) were associated with a lower risk of false-negative FIT results. The presence of proximal ACRN (AOR, 1.59; 95% CI, 1.01-2.51) and adenoma ≥10 mm (AOR, 4.38; 95% CI, 2.17-8.87) were associated with a higher risk of false-negative results. Older age (70 y and above; AOR, 1.67; 95% CI, 1.29-2.17), diverticulum (AOR, 1.94; 95% CI, 1.45-2.58), and hemorrhoid (AOR, 1.63; 95% CI, 1.32-2.01) were associated with false-positive results.

CONCLUSIONS

Subjects with a higher risk of false-negative results should be prioritized for earlier colonoscopy and subjects with inaccurate results should be more cautiously considered for screening by using modalities other than FIT. Our findings will contribute to individualization of screening programs.