The big picture: does colonoscopy work?

Association between improved adenoma detection rates and interval colorectal cancer rates after a quality improvement program

BACKGROUND AND AIMS

Although colonoscopy reduces colorectal cancer (CRC) risk, interval CRCs (iCRCs) still occur. We aimed to determine iCRC incidence, assess the relationship between adenoma detection rates (ADRs) and iCRC rates, and evaluate iCRC rates over time concomitant with initiation of an institutional colonoscopy quality improvement (QI) program.

METHODS

We performed a retrospective cohort study of patients who underwent colonoscopy at an academic medical center (January 2003 to December 2015). We identified iCRCs through our data warehouse and reviewed charts to confirm appropriateness for study inclusion. iCRC was defined as a cancer diagnosed 6 to 60 months and early iCRC as a cancer diagnosed 6 to 36 months after index colonoscopy. We measured the relationship between provider ADRs and iCRC rates and assessed iCRC rates over time with initiation of a QI program that started in 2010.

RESULTS

A total of 193,939 colonoscopies were performed over the study period. We identified 186 patients with iCRC. The overall iCRC rate was .12% and the early iCRC rate .06%. Average-risk patients undergoing colonoscopy by endoscopists in the highest ADR quartile (34%-52%) had a 4-fold lower iCRC risk (relative risk, .23; 95% confidence interval, .11-.48) than those undergoing colonoscopy by endoscopists in the lowest quartile (12%-21%). After QI program initiation, overall iCRC rates improved from .15% to .08% (P < .001) and early iCRC rates improved from .07% to .04% (P = .004).

CONCLUSIONS

We confirmed that iCRC rate is inversely correlated with provider ADR. ADRs increased and iCRC rates decreased over time, concomitant with a QI program focused on split-dose bowel preparation, quality metric measurement, provider education, and feedback. iCRC rate measurement should be considered a feasible, outcomes-driven institutional metric of colonoscopy quality.

Comparison of the Boston Bowel Preparation Scale with an Auditable Application of the US Multi-Society Task Force Guidelines

Background

Existing bowel preparation scales (BPS) only modestly predict interval to next colonoscopy. The US Multi-Society Task Force (MSTF) recommends repeating colonoscopies within the year if the preparation does not allow detection of polyps over 5 mm.

Aim

This study aims to assess reliability and validity of an auditable application of the MSTF compared with the Boston BPS (BBPS).

Methods

We compared an auditable application of MSTF guidelines termed the Montreal BPS (MBPS) with the BBPS using a total cut-off score ≥6 with each segment score ≥2 (BBPS2-6). In sensitivity analyses, we applied the MBPS using a cut-off of 3 mm rather than 5 mm and also assessed the BBPS using an adequacy threshold of total score ≥5 (BBPS5). Videos of 83 colonoscopies (eight for intra-rater agreements) were independently evaluated by nine physicians. Weighted kappas quantified intra- and inter-rater agreements. Associations between scores and clinical outcomes were assessed.

Results

The BBPS2-6 and 5 mm MBPS showed moderate to substantial intra-rater agreements (κ=0.44 to 0.63 and κ=0.50 to 0.53, respectively); inter-rater agreements were only fair to moderate and slight to moderate (κ=0.25 to 0.48 and κ=0.19 to 0.50, respectively). Similar results were noted using alternate thresholds of BBPS5 and 3 mm MBPS. No significant associations were found between scores and clinical outcomes.

Conclusion

For all scales, intra-rater kappas were superior to inter-rater values, the latter reflecting at best moderate agreement. This modest performance may reflect the dichotomized interpretation of the scales (adequate versus inadequate), differing from previous publications assessing scores as continuous variables. Further studies are required to optimally interpret bowel preparation scales with regard to interval to next colonoscopy.

Colonoscopic surveillance: quality, guidelines and effectiveness

Colonoscopic surveillance in patients with a personal or family history of colorectal carcinoma or colonic polyps represents a significant workload for endoscopy services. Effective colonoscopic surveillance relies on quality endoscopic examination and appropriate surveillance interval. This review will discuss quality in colonoscopy and review guidelines for surveillance.

Polyp Genetics

The genetic events involved in the transformation of normal colonic epithelium to neoplastic polyps to invasive carcinoma, as initially proposed by Fearon and Vogelstein, form the foundation of our understanding of colorectal cancer. The identification of the polyp as the precursor lesion to colorectal cancer is the basis of many of our current practices for screening, surveillance, and prevention. The last three decades have seen a veritable explosion in our understanding of the molecular events involved in the pathogenesis of colorectal cancer. It is now clear that there are multiple genetic pathways in the polyp to carcinoma sequence. Some polyps previously thought to be nonneoplastic have now been shown to have malignant potential. Finally, increased understanding of the sequence of genetic events has led to the development of targeted therapeutics. The clinical translation of these scientific advances has made a significant impact on the management of patients with colorectal cancer. Accordingly, it is imperative that all clinicians caring for these patients have an understanding of the genetics of colorectal polyps and cancer. In this article, we review the etiology and genetic pathways to carcinoma associated with a range of polyps of the colon and rectum.

[Pathogenetic aspects in precursor lesions of gastrointestinal tumors]

The pathogenesis of precursor lesions of gastrointestinal tumors is manifested in many ways. In the esophagus an aberrant genetic expression of intestinal transcription factors, such as CDX2 is initiated by local environment factors. During the subsequent dysplasia to carcinoma sequence, chromosomal gain and loss of genes occurs. A 4-color fluorescence in situ hybridization (FISH) assay can be applied in dysplasia as well as in Barrett's adenocarcinoma to define prognostic marker combinations. In the gastric carcinogenesis sequence the gene expression of CDX1 is regulatively dependent on an interplay between inflammation and promotor methylation. In the colon sessile serrated adenomas show a sequence with initial BRAF mutation and late onset of MLH1 promotor hypermethylation with consecutive potential cancer progression. This event is accompanied by an increase of intraepithelial lymphocytes, which is an easy to use tool for routine diagnostics using H&E sections. Next generation sequencing (NGS) investigations of germline mutations in colorectal cancer revealed a spectrum of mutations with low penetration in the field of mismatch repair proteins as well as the APC gene. An individual risk stratification for penetration of these germline mutations is necessary. In conclusion, genetics, phenotypes and terminology of gastrointestinal precursor lesions are unified to a mutually influencing concept within medicine.

Optical diagnosis of colorectal neoplasia: A Western perspective

Optical diagnosis is an emerging paradigm in Western endoscopic practice for the colonoscopic management of diminutive polyps, and includes two complementary clinical strategies: 'resect and discard', in which diminutive high-confidence adenomas are identified, and then removed and discarded without pathological assessment; and 'diagnose and leave', where diminutive high-confidence hyperplastic polyps are identified in the rectosigmoid and then left without resection or biopsy. Like other aspects of colonoscopy performance, adoption of optical diagnosis in Western practice is limited by operator dependency and variation in clinical effectiveness. There is substantial potential for optical diagnosis of colorectal neoplasia during colonoscopy to alleviate the rising costs of health care in the West. However, operator dependence in diagnostic performance together with critical system factors such as informed consent, credentialing, medical legal support and reimbursement incentives must be overcome before optical diagnosis of diminutive lesions is considered for widespread adoption in Western clinical practice.

Role of the Aryl Hydrocarbon Receptor in Colon Neoplasia

For both men and women, colorectal cancer (CRC) is the second leading cause of cancer death in the United States, primarily as a consequence of limited therapies for metastatic disease. The aryl hydrocarbon receptor (AhR) is a ligand-dependent transcription factor with diverse functions in detoxification of xenobiotics, inflammatory responses, and tissue homeostasis. Emerging evidence indicates that AhR also plays an important role in regulating intestinal cell proliferation and tumorigenesis. Here, we review both the pro- and anti-carcinogenic properties of AhR signaling and its potential role as a therapeutic target in CRC.