Microsatellite instability in interval colon cancers

Endoscopic diagnosis of sessile serrated adenoma

Sessile serrated adenoma (SSA) is a special type of serrated adenoma, and recent studies have found that SSA has a malignant potential, progresses quickly and is closely related to right-sided colorectal cancer. SSA is usually located in the proximal colon, which is flat and sessile, and for this reason, SSA is difficult to find by conventional endoscopy and has a high rate of missed diagnosis. There is currently an urgent need to develop new endoscopic technologies to raise the diagnosis rate. In this paper, we will review recent progress in the diagnosis of sessile serrated adenoma using new endoscopic technologies.

Accuracy of fecal immunochemical tests for colorectal cancer: systematic review and meta-analysis

BACKGROUND

Performance characteristics of fecal immunochemical tests (FITs) to screen for colorectal cancer (CRC) have been inconsistent.

PURPOSE

To synthesize data about the diagnostic accuracy of FITs for CRC and identify factors affecting its performance characteristics.

DATA SOURCES

Online databases, including MEDLINE and EMBASE, and bibliographies of included studies from 1996 to 2013.

STUDY SELECTION

All studies evaluating the diagnostic accuracy of FITs for CRC in asymptomatic, average-risk adults.

DATA EXTRACTION

Two reviewers independently extracted data and critiqued study quality.

DATA SYNTHESIS

Nineteen eligible studies were included and meta-analyzed. The pooled sensitivity, specificity, positive likelihood ratio, and negative likelihood ratio of FITs for CRC were 0.79 (95% CI, 0.69 to 0.86), 0.94 (CI, 0.92 to 0.95), 13.10 (CI, 10.49 to 16.35), 0.23 (CI, 0.15 to 0.33), respectively, with an overall diagnostic accuracy of 95% (CI, 93% to 97%). There was substantial heterogeneity between studies in both the pooled sensitivity and specificity estimates. Stratifying by cutoff value for a positive test result or removal of discontinued FIT brands resulted in homogeneous sensitivity estimates. Sensitivity for CRC improved with lower assay cutoff values for a positive test result (for example, 0.89 [CI, 0.80 to 0.95] at a cutoff value less than 20 µg/g vs. 0.70 [CI, 0.55 to 0.81] at cutoff values of 20 to 50 µg/g) but with a corresponding decrease in specificity. A single-sample FIT had similar sensitivity and specificity as several samples, independent of FIT brand.

LIMITATIONS

Only English-language articles were included. Lack of data prevented complete subgroup analyses by FIT brand.

CONCLUSION

Fecal immunochemical tests are moderately sensitive, are highly specific, and have high overall diagnostic accuracy for detecting CRC. Diagnostic performance of FITs depends on the cutoff value for a positive test result.

PRIMARY FUNDING SOURCE

National Institute of Diabetes and Digestive and Kidney Diseases and National Cancer Institute.

Low prevalence of microsatellite instability in interval gastric cancers

BACKGROUND AND AIM

Esophagogastroduodenoscopy (EGD) is recommended at 2-year intervals in countries with a high prevalence of gastric cancer. The aim of this study was to determine whether interval gastric cancers that develop within 2 years of a previous complete screening are associated with microsatellite instability (MSI).

METHODS

Newly diagnosed gastric cancer patients who had undergone gastrectomy were included. Of these 459 patients, 177 were classified as interval gastric cancer since they were diagnosed within 2 years of a previous EGD. Noninterval gastric cancer patients were subclassified into 65 patients who underwent previous EGD between the past 2 and 10 years and 217 patients without EGD during the last 10 years. Analysis for MSI was conducted using two mononucleotide and three dinucleotide markers.

RESULTS

MSI was found more frequently in noninterval gastric cancers than in interval gastric cancers (p = 0.009). Interval gastric cancers were associated with a higher prevalence of early gastric cancer (p = 0.006), smaller size (p < 0.001), and lower TNM stages (p = 0.006). On logistic regression analysis, noninterval gastric cancers were related to MSI (p = 0.010) and larger size (≥4 cm) (p = 0.009). Subjects with interval gastric cancer showed better survival than those with noninterval gastric cancer (p = 0.006).

CONCLUSIONS

During a 2-year screening interval, noninterval gastric cancers tend to be larger, more advanced, and associated with MSI. Biannual EGD screening is effective for detecting small gastric cancers at an early stage, but is not useful in detecting gastric cancers with MSI.

Prevention of interval colorectal cancers: what every clinician needs to know

Colonoscopic screening and surveillance have been very effective tools in the fight against colorectal cancer (CRC). Colonoscopy is more than a cancer screening test; it also can prevent CRC by detecting and removing precancerous lesions. Despite this potential, there has been increasing concern about CRCs that occur after a previous colonoscopy and before the next screening/surveillance examination (interval CRCs). The etiology of interval CRC is thought to be caused mostly by missed or incompletely resected lesions on index colonoscopy with some contribution of rapidly progressive new lesions. If this is true, many interval cancers should be preventable by improving colonoscopy technique. There are a variety of strategies to decrease interval CRC rates including use of a split-dosed bowel preparation, optimizing withdrawal technique, ensuring complete polypectomy, and careful pathologic examination of the tissue removed. Furthermore, there should be an increased emphasis on how endoscopists are trained to cultivate high-quality technique throughout their careers. It is important to inform patients that even high-quality colonoscopy is not perfectly sensitive for the detection of advanced neoplasia. Improving colonoscopy quality can decrease interval CRC rates and further decrease CRC incidence and mortality.

[Surveillance colonoscopy: risk of colorectal tumors]

Colonoscopy is currently the technique of choice for the diagnosis of colorectal cancer (CRC), as well as for the identification and resection of precursor lesions. However, its efficacy has been questioned due to evidence that some patients receive a diagnosis of CRC after a recent "negative" colonoscopy. These post-colonoscopy cancers are also known as interval cancers and, in the last few years, there has been interest in identifying their possible causes. The studies presented this year in the congress of the American Gastroenterological Association (AGA), described in the present article, provide important information for identification of the potential causes of neoplasms detected after a recent colonoscopy and propose methods to reduce this risk. Notable among such studies are those on the prevalence of interval colorectal cancer, those aiming to improve the quality of colonoscopy with a view to increasing the detection of neoplastic lesions, such as assessments of bowel cleansing and of the adenoma detection rate, and studies that propose new alternatives in endoscopy and in colon visualization, such as the colon capsule.

EED gene polymorphism in patients with colorectal cancer

BACKGROUND

Our previous work indicated that, first, the embryonic ectoderm development (EED) gene is a candidate gene associated with the pathogenesis of ulcerative colitis (UC) and, second, that the haplotypes of the EED polymorphism are one of the markers for UC susceptibility. The risk of developing colorectal cancer (CRC) increases in patients with inflammatory bowel disease. 


AIM

The present study aimed at determining the association between polymorphisms in the EED gene and CRC. 


METHODS

Genotype analysis of EED single nucleotide polymorphisms (SNPs) was performed with high-resolution melting analysis, and the genotype and allele frequencies of the EED SNPs were compared between CRC patients and healthy controls. The haplotype frequencies of EED for multiple loci were estimated using the expectation maximization (EM) algorithm. 


RESULTS

Our study had a power of 76.6% at a 0.05 significance level. Genotype and allele frequencies of the SNPs and haplotype frequencies of the EED gene in CRC patients were not significantly different from those in healthy controls. Only the allele frequency of g.-1850G>C in the rectal cancer (RC) patient group was significantly different from that of the control group (p=0.04). Similarly, the genotype and allelic frequencies of the EED SNPs for either tumor site (left or right) or tumor stage were not significantly different from those in healthy controls. However, our data show an association between the g.-993G>C polymorphism in the EED gene and the presence of lymph node metastasis in CRC.


CONCLUSIONS

These results suggest that the SNPs of the EED gene might not be associated with susceptibility to CRC. However, this study shows that the allele frequency of g.-1850G>C in the RC patient group was significantly different from that in the control group (p=0.04) and that g.-993G>C may play a role in the lymph node metastatic process of CRC.

Gene expression profiling of serrated polyps identifies annexin A10 as a marker of a sessile serrated adenoma/polyp

Sessile serrated adenomas/polyps (SSA/Ps) are precursors of colon cancer, particularly those that exhibit microsatellite instability. Distinguishing SSA/Ps from the related, but innocuous, microvesicular hyperplastic polyp (MVHP) can be challenging. In this study seven gastrointestinal pathologists reviewed 109 serrated polyps and identified 60 polyps with histological consensus. Microarray analysis was performed on six distal consensus MVHPs < 9 mm, six proximal consensus SSA/Ps > 9 mm, and six normal colon biopsies (three proximal, three distal). Comparative gene expression analysis confirmed the close relationship between SSA/Ps and MVHPs as there was overlapping expression of many genes. However, the gene expression profile in SSA/Ps had stronger and more numerous associations with cancer-related genes compared with MVHPs. Three genes (TFF2, FABP6, and ANXA10) were identified as candidates whose expression can differentiate SSA/Ps from MVHPs, and the differences in expression were confirmed by quantitative RT-PCR. As ANXA10 showed the most promise in differentiating these polyps, the expression of ANXA10 was evaluated by immunohistochemistry in consensus SSA/Ps (n = 26), MVHPs (n = 21), and normal colon (n = 9). Immunohistochemical expression of ANXA10 was not identified in separate samples of normal colon or in the normal colonic epithelium adjacent to the serrated polyps. Consistent with the microarray and quantitative RT-PCR experiments, immunohistochemical expression of ANXA10 was markedly increased in SSA/Ps compared to MVHPs (p < 0.0001). An ANXA10 score ≥ 3 has a sensitivity of 73% and a specificity of 95% in the diagnosis of an SSA/P. In conclusion, we show that SSA/Ps and MVHPs have significant overlap in gene expression, but also important differences, particularly in cancer-related pathways. Expression of ANXA10 may be a potential marker of the serrated pathway to colon cancer.

Colonoscopic polypectomy: current techniques and controversies

Colonoscopic polypectomy is fundamental to effective colonoscopy. Through its impact on the polyp-cancer sequence, colonoscopic polypectomy reduces colorectal cancer incidence and mortality. Because it eliminates electrosurgical risk, cold snaring has emerged as the preferred technique for most small and all diminutive polyps. Few clinical trial data are available on the effectiveness and safety of specific techniques. Polypectomy technique seems highly variable between endoscopists, with some techniques more effective than others are. Further research is needed to investigate operator variation in polypectomy outcomes and establish an evidence base for best practice.

Characteristics and survival of interval and sporadic colorectal cancer patients: a nationwide population-based cohort study

OBJECTIVES

Colorectal cancers (CRCs) diagnosed relatively soon after a colonoscopy are referred to as interval CRCs. It is not clear whether interval CRCs arise from prevalent lesions missed at colonoscopy or represent specific aggressive biology leading to poor survival.

METHODS

Using Danish population-based medical registries (2000-2009), we investigated patients with "interval" CRC diagnosed within 1-5 years of a colonoscopy, and compared them with cases with colonoscopy ≥10 years before diagnosis and to "sporadic" CRCs with no colonoscopy before diagnosis. Multivariate logistic regression was used to explore the association between clinical, demographic, and comorbidity characteristics and interval CRC. We assessed survival using Kaplan-Meier methods and mortality rate ratios (MRRs) using Cox regression, adjusting for covariates including the Charlson Comorbidity Index (CCI 0, 1-2, 3+).

RESULTS

The comparison of the 982 interval CRCs to the 358 patients with CRC ≥10 years after colonoscopy revealed nearly similar characteristics and mortality. In the comparison with the 35,704 sporadic CRCs, interval cases were slightly older (74 vs. 71 years), more likely to be female (54 vs. 48%), have comorbidities (CCI3+: 28 vs. 15%), have proximal tumors (38 vs. 22%), and tumors with mucinous histology (9.1 vs. 7.0%), but stage was similar (metastatic 23 vs. 24%). In logistic regression analysis, female sex, localized stage at diagnosis, proximal tumor location, and high comorbidity burden were factors independently associated with interval CRC. The 1-year survival was 68% (95% confidence interval (CI): 65%, 71%) in interval and 71% (95% CI: 70%, 71%) in sporadic cases, with an adjusted MRR of 0.92 (95% CI 0.82, 1.0). After 5 years, survival was 41% (95% CI: 37%, 44%) in interval and 43% (95% CI: 42%, 43%) in sporadic cases, and the adjusted 2-5 year MRR was 1.0 (95% CI 0.88, 1.2).

CONCLUSIONS

Clinical characteristics and survival among interval CRCs did not suggest aggressive biology, but rather that the majority represented missed lesions.

Serrated colon polyps as precursors to colorectal cancer

Identification of the serrated neoplasia pathway has improved our understanding of the pathogenesis of colorectal cancer (CRC). Insights include an increased recognition of the malignant potential of different types of serrated polyps such as sessile and traditional serrated adenomas. Sessile serrated adenomas share molecular features with colon tumors that have microsatellite instability and a methylator phenotype, indicating that these lesions are precursors that progress via the serrated neoplasia pathway. These data have important implications for clinical practice and CRC prevention, because hyperplastic polyps were previously regarded as having no malignant potential. There is also evidence that the serrated pathway contributes to interval or missed cancers. Endoscopic detection of serrated polyps is a challenge because they are often inconspicuous with indistinct margins and are frequently covered by adherent mucus. It is important for gastroenterologists to recognize the subtle endoscopic features of serrated polyps to facilitate their detection and removal, and thereby ensure a high-quality colonoscopic examination. Recognition of the role of serrated polyps in colon carcinogenesis has led to the inclusion of these lesions in postpolypectomy surveillance guidelines. However, an enhanced effort is needed to identify and completely remove serrated adenomas, with the goal of increasing the effectiveness of colonoscopy to reduce CRC incidence.

Metachronous adenoma on ileorectal anastomosis suture line and submucosal deep invasive cancer suspected of rapid growth in rectal remnant following long-term interval after curative surgery for advanced colon cancer

There is general agreement as to the value of postoperative surveillance and the effectiveness of colonoscopy in the early detection of metachronous colorectal lesions. In the present case, a 56-year-old woman with no family history of colon cancer underwent surveillance colonoscopy in which a metachronous flat adenoma was detected following an interval of 23 years after a colectomy and 20 years subsequent to treatment for uterine cancer. A second metachronous flat lesion histopathologically determined to be a submucosal (sm) deep invasive cancer with lymphovascular involvement was detected 12 months later. This second metachronous lesion was suspected of having developed rapidly in the rectal remnant accounting for its sm deep invasion. The findings of this case suggest colonoscopy surveillance guidelines proposed for individuals at high risk should be evaluated based on cancer history and an analysis of possible mismatch repair gene mutations. In addition, the first metachronous lesion was located directly on the suture line of the anastomosis. Endoscopic submucosal dissection (ESD) was indicated despite severe fibrosis into the sm layer. This case also demonstrates the successful use of improved ESD instruments, sm injection agents and technique refinements in the treatment of a technically difficult lesion with a high risk of complications.

Advanced precancerous lesions (APL) in the colonic mucosa

Colorectal cancer is a leading cause of cancer death worldwide. Most colorectal cancers are preventable. Surveillance colonoscopy is used to detect and remove precancerous lesions. Although the majority of precancerous lesions develop sporadically, some have an inherited component. In this review, we summarize the clinical, pathologic, and molecular features of advanced precancerous lesions of the colon. The most common and clinically important intestinal polyposis syndromes, and their genetics, are also discussed. Finally, current recommendations regarding the treatment and surveillance of precancerous lesions, both in the sporadic and in inherited setting, are reviewed.

Serrated polyps of the large intestine: current understanding of diagnosis, pathogenesis, and clinical management

Approximately 30% of colorectal carcinomas develop via the serrated neoplasia pathway characterized by widespread DNA methylation and frequent BRAF mutation. Serrated polyps represent a heterogeneous group of polyps which are the precursor lesions to serrated pathway colorectal carcinomas. The histological classification of serrated polyps has evolved over the last two decades to distinguish three separate entities: hyperplastic polyp, sessile serrated adenoma (SSA), and traditional serrated adenoma (TSA). The malignant potential of SSAs and TSAs has been clearly demonstrated. SSAs are more challenging to detect by colonoscopy and are likely to account for some interval carcinomas of the proximal colon. Serrated polyposis syndrome is now widely recognized as conferring a high risk of colorectal carcinoma although its cause remains elusive. The current understanding of the actual malignant potential of each serrated polyp subtype is still limited due to the lack of large-scale prospective studies. Patient management guidelines have been recently updated although high-level evidence to support them is still required.

Incomplete polyp resection during colonoscopy-results of the complete adenoma resection (CARE) study

BACKGROUND & AIMS

Although the adenoma detection rate is used as a measure of colonoscopy quality, there are limited data on the quality of endoscopic resection of detected adenomas. We determined the rate of incompletely resected neoplastic polyps in clinical practice.

METHODS

We performed a prospective study on 1427 patients who underwent colonoscopy at 2 medical centers and had at least 1 nonpedunculated polyp (5-20 mm). After polyp removal was considered complete macroscopically, biopsies were obtained from the resection margin. The main outcome was the percentage of incompletely resected neoplastic polyps (incomplete resection rate [IRR]) determined by the presence of neoplastic tissue in post-polypectomy biopsies. Associations between IRR and polyp size, morphology, histology, and endoscopist were assessed by regression analysis.

RESULTS

Of 346 neoplastic polyps (269 patients; 84.0% men; mean age, 63.4 years) removed by 11 gastroenterologists, 10.1% were incompletely resected. IRR increased with polyp size and was significantly higher for large (10-20 mm) than small (5-9 mm) neoplastic polyps (17.3% vs 6.8%; relative risk = 2.1), and for sessile serrated adenomas/polyps than for conventional adenomas (31.0% vs 7.2%; relative risk = 3.7). The IRR for endoscopists with at least 20 polypectomies ranged from 6.5% to 22.7%; there was a 3.4-fold difference between the highest and lowest IRR after adjusting for size and sessile serrated histology.

CONCLUSIONS

Neoplastic polyps are often incompletely resected, and the rate of incomplete resection varies broadly among endoscopists. Incomplete resection might contribute to the development of colon cancers after colonoscopy (interval cancers). Efforts are needed to ensure complete resection, especially of larger lesions. ClinicalTrials.gov Number: NCT01224444.

Polyps with advanced neoplasia are smaller in the right than in the left colon: implications for colorectal cancer screening

BACKGROUND & AIMS

Colonoscopy is consistently associated with reduced left-sided, but not right-sided, colorectal cancer (CRC) incidence and mortality. This might be because polyps with advanced pathology are smaller and more easily missed in the right vs left colon. We explored this postulate by evaluating the relationship among size, location, and histology of polyps from a large nationwide sample.

METHODS

We conducted a cross-sectional study of 233,414 polyps from 142,686 patients (47% women; mean age, 60 years), which were reviewed by Miraca Life Sciences in 2009. We assessed polyp histology, location, and size of largest fragment submitted. We compared size distribution of right vs left polyps with high-grade dysplasia (HGD) or adenocarcinoma as well as any advanced neoplasia.

RESULTS

The average size of right-sided polyps was smaller than that of left-sided polyps with HGD or adenocarcinoma (8.2 vs 12.4 mm, respectively); the same was true for polyps with advanced neoplasia (7.6 vs 11.1 mm, respectively) (P < .001). Most right-sided polyps with HGD, adenocarcinoma, or any advanced neoplasia were ≤9 mm, whereas most left-sided polyps with these findings were >9 mm. Polyps with advanced pathology were 5-fold more likely to be <6 mm in the right vs left colon: odds ratio, 5.27; 95% confidence interval, 4.06-6.82 for HGD or adenocarcinoma; odds ratio, 4.89; 95% confidence interval, 4.34-5.51 for advanced neoplasia.

CONCLUSIONS

Polyps with features of HGD, adenocarcinoma, or advanced neoplasia were significantly smaller in the right vs left colon. Strategies to prevent right-sided CRC require more accurate detection of small, advanced polyps.

Prevalence of proximal colon serrated polyps in a population at average risk undergoing screening colonoscopy: a multicenter study

BACKGROUND/AIMS

Proximal serrated polyp (SP) is one of potential explanations for the failure of colonoscopy to prevent all interval cancers. The aims of our study were to determine the prevalence of proximal SP in Korea and to investigate clinical factors associated with the proximal SP detection in average-risk people undergoing screening colonoscopy.

METHODS

We re-analyzed the data of the previous prospective study which included asymptomatic, average-risk people over 45 years of age who underwent screening colonoscopy from four tertiary medical centers in South Korea between December 2007 and November 2008 to compare guaiac-based and quantitative immunochemical fecal occult blood tests. SPs included hyperplastic polyps, sessile serrated adenomas, and traditional serrated adenomas.

RESULTS

A total of 926 subjects were analyzed. Of these, 454 subjects (49.0%) and 356 (38.4%) had a total of 859 polyps and 709 adenomas, respectively. One hundred and ten subjects (11.9%) had a total of 150 SPs and 49 (5.3%) had a total of 60 proximal SPs. In comparison between subjects with and without proximal SP, there were no differences with respect to procedure-related variables including endoscopic training, day of week, time of day, and elapsed time as well as demographic features such as age and sex.

CONCLUSIONS

In average-risk people underwent screening colonoscopy, the prevalence of proximal SP was 5.3% in Korea. There were no significant clinical factors associated with the proximal SP detection.

Laterally spreading tumors in the colon and rectum

The large and relatively flat colorectal neoplastic lesions called laterally spreading tumors are classified as nonpolypoid despite some mixed patterns with protruding nodules. Large hyperplastic polyps and sessile serrated lesions are non-neoplastic lesions that also have this morphology and may potentially progress to neoplasia. All these large and relatively flat lesions are more frequent in the proximal colon and less conspicuous than polypoid lesions. Their underdiagnosis is a major factor in the failure of colonoscopy to prevent cancer in the proximal colon. The treatment of laterally spreading tumors by endoscopic resection (endoscopic mucosal resection, piecemeal endoscopic mucosal resection, endoscopic submucosal dissection), or by surgery is based on a careful morphologic analysis, taking into account the size and surface with nodules or depression. The technique of endoscopic submucosal dissection should be diffused because it reduces the number of surgical indications.

Hyperplastic polyps identified during screening endoscopy: reevaluated by histological examinations and genetic alterations

BACKGROUND/PURPOSE

Screening colonoscopy is one of the most effective methods to detect and prevent colorectal cancer by removing neoplastic polyps. The recent discovery of serrated polyps with neoplastic potential has reclassified these polyps into hyperplastic polyps (HPs), sessile serrated adenoma (SSA), and traditional serrated adenoma (TSA) on the basis of macroscopic morphology and microscopic histology. In this study, we aimed to revisit HPs identified during screening endoscopy by histological reevaluation and genetic alterations.

METHODS

A total of 253 HPs found by screening endoscopy were rechecked by two pathologists, and mutual agreement on the diagnosis of polyps was subjected for further statistical analysis. Direct sequencing for gene mutation at BRAF V600E and KRAS G12D was performed.

RESULTS

Among the 253 HPs analyzed, 175 were classified as serrated polyps, while 78 were reclassified into other diagnosis. The concordance among pathologists in diagnosing these serrated polyps was substantial (κ = 0.6672). About 11.5% of the reviewed HPs turned out to be with neoplastic potential, including 7 SSAs, 5 TSAs, as well as 17 conventional adenomas. Results of subgroup analyses revealed that polyps >10 mm were more likely to be found in proximal colon (p = 0.0006) and tended to harbor neoplastic components. We found that two SSAs and one TSA had BRAF mutation, while one TSA had KRAS mutation. The mean size of these mutated adenomas (9.0 mm) was larger than those with wild-type genes (4.9 mm).

CONCLUSION

Serrated polyps with neoplastic potential were prone to be overlooked as hyperplastic and innocent ones during screening colonoscopy. Therefore, both endoscopists and pathologists should pay attention to understand the importance of recognizing serrated adenomas, especially for those polyps >10 mm, or those that are located in the proximal colon.

Interval cancers after colonoscopy-insights and recommendations

Several studies have raised warnings about the limited effectiveness of colonoscopy for the prevention of colorectal cancer (CRC), especially of the proximal colon. Two major categories of factors might be responsible for the development of interval cancers, namely technical, endoscopist-dependent factors and biological characteristics of the cancer that lead to more rapid tumour progression. Recognition of endoscopist-dependent factors is critical, as these factors are probably amenable to correction through improved awareness and education of endoscopists, using quality metrics (such as adenoma detection rates and cecal intubation rates) for objective evaluation and feedback. In this article, the current literature regarding the incidence of, and potential explanations for, interval CRCs is outlined. Although there is probably an interaction between technical and biology-related factors--and an attempt to dissect the biology from the technology might be fraught with difficulties--a structured analysis of individual cases of interval cancer might help in the continuous monitoring of the quality of colonoscopy, and ultimately might reduce the number of interval CRCs.

Wide field endoscopic resection for advanced colonic mucosal neoplasia: current status and future directions

Most colonic adenomas are ≤ 10 mm and are routinely treated by colonoscopic polypectomy with long-term health benefits. Nonpolypoid lesions ≥ 20 mm, whether sessile or flat and laterally spreading, are forms of advanced mucosal neoplasia that cannot be managed by conventional polypectomy and are often referred for surgery. However, the majority of these lesions when carefully assessed are found to be noninvasive and can be safely and effectively treated by advanced endoscopic techniques including endoscopic mucosal resection or endoscopic submucosal dissection with resultant cost, morbidity, and mortality benefits. Lesion assessment is a critical component. Enhanced imaging methods provide the opportunity for accurate pathological characterization, informing treatment decisions, without the need for previous histologic confirmation. Techniques of advanced endoscopic resection are still in evolution and further improvements, including hybrid techniques, bringing less technically challenging and shorter procedures with superior safety can be reasonably expected in the next decade. Safety is a fundamental consideration. Methods of early recognition of complications, risk stratification, and management pathways are being developed and refined. Standardization, validation, and adoption of these technological developments will improve endoscopic interpretation and therapy and in combination with an increased understanding of adenoma molecular biology, will result in a progressively more individualized lesion-specific endoscopic approach. The future of advanced endoscopic resection in the colon is promising, and the next few years should see the boundaries of endoscopic resection expand well beyond the limits of what we know today.

Serrated lesions of the colorectum: review and recommendations from an expert panel

Serrated lesions of the colorectum are the precursors of perhaps one-third of colorectal cancers (CRCs). Cancers arising in serrated lesions are usually in the proximal colon, and account for a disproportionate fraction of cancer identified after colonoscopy. We sought to provide guidance for the clinical management of serrated colorectal lesions based on current evidence and expert opinion regarding definitions, classification, and significance of serrated lesions. A consensus conference was held over 2 days reviewing the topic of serrated lesions from the perspectives of histology, molecular biology, epidemiology, clinical aspects, and serrated polyposis. Serrated lesions should be classified pathologically according to the World Health Organization criteria as hyperplastic polyp, sessile serrated adenoma/polyp (SSA/P) with or without cytological dysplasia, or traditional serrated adenoma (TSA). SSA/P and TSA are premalignant lesions, but SSA/P is the principal serrated precursor of CRCs. Serrated lesions have a distinct endoscopic appearance, and several lines of evidence suggest that on average they are more difficult to detect than conventional adenomatous polyps. Effective colonoscopy requires an endoscopist trained in the endoscopic appearance of serrated lesions. We recommend that all serrated lesions proximal to the sigmoid colon and all serrated lesions in the rectosigmoid > 5 mm in size, be completely removed. Recommendations are made for post-polypectomy surveillance of serrated lesions and for surveillance of serrated polyposis patients and their relatives.

Invasive colorectal cancer within 5 years of negative colonoscopy in a Japanese population

AIM

Colonoscopy provides imperfect protection against colorectal cancer (CRC). In an attempt to improve cancer detection we evaluated the clinical features of invasive CRC detected within 5 years of a negative colonoscopy.

METHOD

The details of colonoscopies performed in a rural hospital in Japan were prospectively recorded at the time of the examination. The patients were followed over 5 years for the subsequent occurrence of cancer.

RESULTS

In a 5-year period, 10148 patients underwent colonoscopy and 202 without previous colonoscopy were diagnosed with invasive CRC. Of 3212 patients with a colonoscopy negative for cancer, nine developed invasive cancer within 5 years. The ratios for invasive CRC detected without/with previous colonoscopy were 60:1 in the rectum, 54:1 in the sigmoid colon, 15:1 in the descending colon, 28:0 in the transverse colon, 31:5 in the ascending colon and 14:1 in the caecum (P=0.041). The ratio between left- and right-sided colonic cancer was also significantly different (129:3 and 45:6, P=0.0078). Six (67%) of the invasive CRCs were in the ascending colon or caecum. Five of six patients with invasive CRC in the ascending colon and caecum had right-sided small adenomas at prior colonoscopy.

CONCLUSION

The majority of early/missed CRCs were right-sided and associated with prior right-sided colonic adenomas. Repeated colonoscopy of patients with right-sided adenomas at a shorter surveillance interval deserves consideration.

Colorectal endoscopy, advanced adenomas, and sessile serrated polyps: implications for proximal colon cancer

OBJECTIVES

Colonoscopy is associated with a decreased risk of colorectal cancer but may be more effective in reducing the risk of distal than proximal malignancies. To gain insight into the differences between proximal and distal colon endoscopic performance, we conducted a case-control study of advanced adenomas, the primary targets of colorectal endoscopy screening, and sessile serrated polyps (SSPs), newly recognized precursor lesions for a colorectal cancer subset that occurs most often in the proximal colon.

METHODS

The Group Health-based study population included 213 advanced adenoma cases, 172 SSP cases, and 1,704 controls aged 50-79 years, who received an index colonoscopy from 1998-2007. All participants completed a structured questionnaire covering endoscopy history. Participants with polyps underwent a standard pathology review to confirm the diagnosis and reclassify a subset as advanced adenomas or SSPs. Logistic regression analyses were conducted to estimate adjusted odds ratios (OR) and 95% confidence intervals (CI) for the association between endoscopy and advanced adenomas and SSPs separately; site-specific analyses were completed.

RESULTS

Previous endoscopy was inversely associated with advanced adenomas in both the rectum/distal colon (OR=0.38; 95% CI: 0.26-0.56) and proximal colon (OR=0.31; 95% CI: 0.19-0.52), but there was no statistically significant association between previous endoscopy and SSPs (OR=0.80; 95%CI: 0.56-1.13).

CONCLUSIONS

Our results support the hypothesis that the effect of endoscopy differs between advanced adenomas and SSPs. This may have implications for proximal colon cancer prevention and be due to the failure of endoscopy to detect/remove SSPs, or the hypothesized rapid development of SSPs.

Concerns and challenges in flexible sigmoidoscopy screening

In 1992, two well-conducted case-control studies used data from two different health maintenance organizations and demonstrated a 59-79% reduction in mortality from colorectal cancer (CRC) following exposure to sigmoidoscopy. These studies highlight the possibility of reducing mortality from CRC using population-based endoscopic screening. The development of fiber optics improved the technology, and the ease of performing flexible sigmoidoscopy (FS) with widespread adoption of this screening modality. To date, FS is the only endoscopic screening modality that has been shown to reduce mortality in randomized clinical trials. This article reviews the development of sigmoidoscopy, its use in CRC screening and the current reduced role of this proven screening modality, and explores new frontiers for population-based FS screening.

Comparison of screen-detected and interval colorectal cancers in the Bowel Cancer Screening Programme

Background:

The NHS Bowel Cancer Screening Programme (BCSP) offers biennial faecal occult blood testing (FOBt) followed by colonoscopy after positive results. Colorectal cancers (CRCs) registered with the Northern Colorectal Cancer Audit Group database were cross-referenced with the BCSP database to analyse their screening history.

Methods:

The CRCs in the screening population between April 2007 and March 2010 were identified and classified into four groups: control (diagnosed before first screening invite), screen-detected, interval (diagnosed between screening rounds after a negative FOBt), and non-uptake (declined screening). Patient demographics, tumour characteristics and survival were compared between groups.

Results:

In all, 511 out of 1336 (38.2%) CRCs were controls; 825 (61.8%) were in individuals invited for screening of which 322 (39.0%) were screen detected, 311 (37.7%) were in the non-uptake group, and 192 (23.3%) were interval cancers. Compared with the control and interval cancer group, the screen-detected group had a higher proportion of men (P=0.002, P=0.003 respectively), left colon tumours (P=0.007, P=0.003), and superior survival (both P<0.001). There was no difference in demographics, tumour location/stage, or survival between control and interval groups.

Conclusion:

The FOBt is better at detecting cancers in the left colon and in men. The significant numbers of interval cancers weren’t found to have an improved outcome compared with the non-screened population.

Prevalence and predictors of interval colorectal cancers in medicare beneficiaries

BACKGROUND

After a colonoscopy that is negative for cancer, a subset of patients may be diagnosed with colorectal cancer, also termed interval cancer. The frequency and predictors have not been well studied in a population-based US cohort.

METHODS

The authors used the linked Surveillance, Epidemiology, and End Results (SEER)-Medicare database to identify 57,839 patients aged ≥ 69 years who were diagnosed with colorectal cancer between 1994 and 2005 and who underwent colonoscopy within 6 months of cancer diagnosis. Colonoscopy performed between 6 and 36 months before cancer diagnosis was a proxy for interval cancer.

RESULTS

By using the case definition, 7.2% of patients developed interval cancers. Factors that were associated with interval cancers included proximal tumor location (distal colon: multivariable odds ratio [OR], 0.42; 95% confidence interval [CI], 0.390-0.46; rectum: OR, 0.47; 95% CI, 0.42-0.53), increased comorbidity (OR, 1.89; 95% CI, 1.68 2.14 for ≥ 3 comorbidities), a previous diagnosis of diverticulosis (OR, 6.00; 95% CI, 5.57-6.46), and prior polypectomy (OR, 1.74; 95% CI, 1.62-1.87). Risk factors at the endoscopist level included a lower polypectomy rate (OR, 0.70; 95% CI, 0.63-0.78 for the highest quartile), higher colonoscopy volume (OR, 1.27; 95% CI, 1.13-1.43), and specialty other than gastroenterology (colorectal surgery: OR, 1.45; 95% CI, 1.16-1.83; general surgery: OR, 1.42; 95% CI, 1.24-1.62; internal medicine: OR, 1.38; 95% CI, 1.17-1.63; family practice: OR, 1.16; 95% CI, 1.00-1.35).

CONCLUSIONS

A significant proportion of patients developed interval colorectal cancer, particularly in the proximal colon. Contributing factors likely included both procedural and biologic factors, emphasizing the importance of meticulous examination of the mucosa.

Is KRAS mutation associated with interval colorectal cancers?

BACKGROUND

Colorectal cancers diagnosed in the interval after a complete colonoscopy may occur due to rapid tumor growth. Interval colorectal cancers are associated with microsatellite instability (MSI).

AIMS

Our aim was to study the association of KRAS mutation with interval colorectal cancers and MSI.

METHODS

We searched our institution's cancer registry for interval colorectal cancers, defined as colorectal cancers that developed within 5 years of a complete colonoscopy. These were frequency matched to patients with non-interval colorectal cancers. Archived cancer specimens were evaluated for KRAS mutations in codons 12 and 13 using sequencing, and MSI by sequencing microsatellite loci. Multivariable logistic regression was used to analyze the association between KRAS mutation status, MSI status and interval colorectal cancers.

RESULTS

There were 63 interval and 131 non-interval colorectal cancers. KRAS mutation was present in 12.9% of interval cancers compared to 28.9% of non-interval cancers (P = 0.03). In multivariable logistic regression model, KRAS was inversely associated with interval cancers (OR 0.36; 95% CI 0.15-0.90). In Cox proportional hazards model, adjusting for age, tumor grade, TNM Stage and MSI status, we found no association between KRAS mutation and 5-year survival compared to cancers without KRAS mutation (HR 0.84; 95% CI 0.4-1.46; P = 0.5).

CONCLUSIONS

KRAS mutation is inversely associated with interval cancers and with MSI, suggesting that it is a marker of the chromosomal instability pathway associated with slow tumor growth, and distinct from MSI rapidly growing cancers. Molecular characterization of colorectal cancers is helpful in determining underlying pathway and may determine therapy.

Korean guidelines for postpolypectomy colonoscopy surveillance

Postpolypectomy surveillance has become a major indication for colonoscopy as a result of increased use of screening colonoscopy in Korea. In this report, a careful analytic approach was used to address all available evidences to delineate the predictors for advanced neoplasia at surveillance colonoscopy and we elucidated the high risk findings of the index colonoscopy as follows: 3 or more adenomas, any adenoma larger than 10 mm, any tubulovillous or villous adenoma, any adenoma with high-grade dysplasia, and any serrated polyps larger than 10 mm. Surveillance colonoscopy should be performed five years after the index colonoscopy for those without any high-risk findings and three years after the index colonoscopy for those with one or more high risk findings. However, the surveillance interval can be shortened considering the quality of the index colonoscopy, the completeness of polypectomy, the patient's general condition, and family and medical history.

Clinicopathological features of serrated adenocarcinoma defined by Mäkinen in dukes' B colorectal carcinoma

OBJECTIVE

Serrated adenocarcinoma (SAC), proposed as a new pathologic type, arises predominantly in the right side of the colon and has a poorer prognosis than conventional colorectal carcinoma. The prognosis of colorectal carcinoma is variable in Dukes' B, so the aim of this study was to determine whether or not SAC has a poor prognosis in Dukes' B.

METHODS

The study group comprised 64 patients who underwent surgery for colorectal carcinoma. We undertook a statistical analysis of the association of SAC and non-SAC with sex, age, histologic type, depth of tumor, location of tumor, venous invasion and lymphatic invasion.

RESULTS

SACs were encountered in 17.5% of cases (n = 11). SAC had a less favorable 5-year survival than non-SAC (p = 0.0396 log-rank, Kaplan-Meier). The factors that achieved statistical significance in the univariate analysis were subsequently included in a multivariate analysis and we found that SAC was an independent factor (p = 0.027).

CONCLUSIONS

SAC has a poor prognosis and is not affected by other factors confirming that SAC is an independently less favorable prognostic factor.

Colorectal cancers not detected by screening flexible sigmoidoscopy in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial

BACKGROUND AND OBJECTIVE

Diagnosis of colorectal cancer after negative findings on endoscopic evaluation raises concern about the effectiveness of endoscopic screening. We contrast screening-detected cancers with cancers not detected by screening among participants assigned to flexible sigmoidoscopy (FSG) in the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial to determine the reasons for the lack of detection of prevalent lesions.

DESIGN

Cancers detected within 1 year of a screening FSG with abnormal findings were classified as screening detected. All other cancers were categorized, based on cancer stage and years until detection, as either not detectable or prevalent but not detected at the time of screening.

SETTING/PATIENTS

A total of 77,447 subjects in the multicenter PLCO trial.

MAIN OUTCOME MEASUREMENTS

A total of 977 colorectal cancers were diagnosed with a mean follow-up of 11.5 years.

RESULTS

A total of 243 (24.9%) cancers were screening detected, 470 (48.1%) were not detectable at screening, and 264 (27.0%) were considered prevalent but not detected. Among prevalent nondetected lesions, 35.6% (n = 94) were attributed to problems in patient compliance (58 never screened, 34 delayed colonoscopy follow-up, and 2 inadequate bowel preparation), 43.9% (n = 116) were attributable to a limitation in the FSG procedure (97 beyond the reach of the sigmoidoscope and 19 inadequate depth of insertion on FSG), and 20.5% (n = 54) were caused by endoscopist limitation (33 missed on FSG, 21 missed at initial colonoscopy) (P < .0001). Had colonoscopy instead of FSG been used for screening, an additional 15.6% and as many as 19.0% of cancers may have been screening-detected.

LIMITATIONS

These estimates are reasonable approximations, but biological variability precludes precise determinations.

CONCLUSIONS

Prevalent nondetected cancers were more often attributable to problems with patient compliance or limitations in the FSG procedure than to missed lesions. Colonoscopy instead of FSG could have moderately increased the detection of cancer via screening.

Editorial: sessile serrated adenomas and their pit patterns: we must first see the forest through the trees

Serrated lesions of the colorectum include hyperplastic polyps, which are non-neoplastic, and sessile serrated adenomas (SSAs, also known as sessile serrated polyps) and traditional serrated adenomas, which are premalignant. It is believed that up to 30% of colon cancers and many post-colonoscopy cancers arise from serrated neoplasms. Post-colonoscopy cancers have been found to have a molecular signature similar to SSAs, including CpG island methylation, BRAF mutations, and microsatellite instability. A novel pit pattern, Type II-O, has been demonstrated to have a high specificity for SSAs. Unfortunately, the sensitivity is too low to utilize a Type II-O pit pattern to determine which serrated lesion is neoplastic and needs resection. Moreover, there is significant endoscopist-related variability in the detection of serrated lesions of the colon. Efforts to improve the detection of serrated neoplasms are warranted.

[Serrated precursor lesions]

The so-called serrated pathway has in recent years been well established as a second route of colorectal carcinogenesis. Sessile serrated polyps, especially sessile serrated adenomas (SSA) and traditional serrated adenomas (TSA) were identified as precursor lesions of this pathway. Activating mutations in either the BRAF (in SSAs) or the KRAS oncogene (in TSAs) have been determined as the initiating molecular alterations, followed by epigenetic methylation of CpG islands in promoter regions of genes which are implicated in cell cycle control or DNA repair. These findings have led to a paradigm shift in gastrointestinal pathology as lesions without cytological dysplasia, such as SSAs and certain forms of hyperplastic polyps, are now accepted to be precancerous lesions. In addition, carcinomas that have developed through the serrated pathway of colorectal carcinogenesis show varying biological behavior relevant for the clinical management of these tumors depending on the molecular aberrations.

The detection of premalignant colon polyps during colonoscopy is stable throughout the workday

BACKGROUND

Recent studies have shown that colonoscopic polyp detection decreases as the workday progresses. This may reflect time-dependent factors such as colonoscopist fatigue and decreased colon cleanliness, which can be addressed through adaptations in colonoscopy practice.

OBJECTIVE

To test for time-of-day differences in adenomatous polyp (AP) and sessile serrated polyp (SSP) detection in a practice that uses split-dose bowel preparation and moderated daily colonoscopist procedure loads.

DESIGN

Retrospective chart review.

SETTING

Community-based, group gastroenterology practice.

PATIENTS

This study involved 2439 patients undergoing surveillance or screening colonoscopy.

INTERVENTION

Colonoscopy.

MAIN OUTCOME MEASUREMENTS

Detection rate of all premalignant polyps (PMPs), and of APs and SSPs, individually.

RESULTS

A total of 1183 PMPs were identified in 1486 eligible patients (mean PMP/colonoscopy = 0.80; PMP detection rate = 47%). In univariate and multivariate analyses, PMP detection as well as detection of APs or SSPs individually did not vary significantly in relation to the hour of the day. In a binary comparison of morning (am) versus afternoon (pm) procedures, the total polyp detection rate was 67% and 66%, respectively. For PMPs, APs, SSPs, and hyperplastic polyps (HPs), the am and pm detection rates were 46% and 47%, 41% and 44%, 8% and 8%, and 27% and 24%, respectively. Bowel preparation quality was independent of time of day and was rated excellent or good in 86% to 87% of cases.

LIMITATIONS

Retrospective, nonrandomized study.

CONCLUSION

Stable PMP, AP, SSP, and HP detection rates throughout the workday occur under certain practice conditions, including the use of split-dose bowel preparation and/or moderated daily colonoscopist procedure loads.

The clinical significance of serrated polyps

Colorectal cancer (CRC) is a heterogeneous disorder than arises via multiple distinct pathways, such as the serrated pathway, in which serrated polyps (including variants of hyperplastic polyps) are the precursor lesions. Approximately 15-20% of all CRCs arise via the serrated pathway, and these serrated carcinomas are clinically, morphologically, and molecularly distinct from conventional CRCs. The prevention of serrated carcinomas represents an important clinical challenge. Gastroenterologists need to recognize and remove potential precursor lesions and implement a post-polypectomy surveillance program when appropriate. This article focuses on the characteristics and significance of clinically relevant serrated polyps and addresses implications for CRC prevention practices.

Prevalence and variable detection of proximal colon serrated polyps during screening colonoscopy

BACKGROUND & AIMS

Colonoscopy may have a greater protective effect for distal colorectal cancer (CRC) than proximal CRC. Serrated polyps are frequently located in the proximal colon, can be missed during colonoscopy, and may progress to CRC. We investigated the prevalence and endoscopist detection rates of proximal serrated polyps in a large cohort of average risk patients undergoing screening colonoscopy.

METHODS

Screening colonoscopies performed by 15 attending gastroenterologists at 2 academic endoscopy units between 2000 and 2009 were reviewed. Serrated polyps included hyperplastic polyps, sessile serrated adenomas, and traditional serrated adenomas. Endoscopist-level detection rates for adenomas and serrated polyps were calculated. Pearson correlation coefficients were calculated to evaluate the associations of adenoma and proximal serrated polyp detection rates. Logistic regression was used to compare endoscopists' detection rates.

RESULTS

A total of 11,049 polyps were detected in 6681 colonoscopies (adenomas: 5637, 51%; serrated: 3984, 36%; proximal serrated: 1238, 11%). The proportion of colonoscopies with at least one proximal serrated polyp was 13% (range 1%-18%). Proximal serrated polyp detection rates per colonoscopy ranged from 0.01 to 0.26. Adenoma and proximal serrated polyp detection rates per colonoscopy were strongly correlated (R = 0.76, P = .0005). The odds of detecting at least one proximal serrated polyp for individual endoscopists ranged from 0.05 to 0.67 compared to the highest level detector. Endoscopist (P < .0001), but not patient age (P = .76) or gender (P = .95), was associated with proximal serrated polyp detection.

CONCLUSIONS

In an average-risk screening cohort, the detection of proximal serrated polyps was highly variable and endoscopist dependent. A significant proportion of proximal serrated polyps may be missed during colonoscopy. High-quality colonoscopy is important for the detection and resection of all polyps with neoplastic potential.

Light-scattering technologies for field carcinogenesis detection: a modality for endoscopic prescreening

Colonoscopy has revolutionized colorectal cancer (CRC) screening resulting in a decrease in both CRC mortality and incidence. Despite this, CRC still ranks as the second leading cause of cancer deaths among Americans underscoring the need to both increase availability and accuracy of colonoscopy. The latter considerations provide the impetus for much of the current research into adjunctive imaging technologies. Recent advances in improving detection of dysplasia that have translated into clinical practice include high-definition scopes, narrow-band imaging, and chromo-endoscopy. Another major direction of research into improving endoscopy is determining histology of lesions in situ (“optical biopsy”) with confocal endomicroscopy, fluorescence and elastic scattering spectroscopy. All these techniques are of great promise in improving delivery of endoscopy but, to date, have not addressed the potentially more important hurdle associated with logistic challenges of providing accurate CRC screening for the entire at-risk population.

Colorectal cancer screening for average-risk North Americans: an economic evaluation

BACKGROUND

Colorectal cancer (CRC) fulfills the World Health Organization criteria for mass screening, but screening uptake is low in most countries. CRC screening is resource intensive, and it is unclear if an optimal strategy exists. The objective of this study was to perform an economic evaluation of CRC screening in average risk North American individuals considering all relevant screening modalities and current CRC treatment costs.

METHODS AND FINDINGS

An incremental cost-utility analysis using a Markov model was performed comparing guaiac-based fecal occult blood test (FOBT) or fecal immunochemical test (FIT) annually, fecal DNA every 3 years, flexible sigmoidoscopy or computed tomographic colonography every 5 years, and colonoscopy every 10 years. All strategies were also compared to a no screening natural history arm. Given that different FIT assays and collection methods have been previously tested, three distinct FIT testing strategies were considered, on the basis of studies that have reported "low," "mid," and "high" test performance characteristics for detecting adenomas and CRC. Adenoma and CRC prevalence rates were based on a recent systematic review whereas screening adherence, test performance, and CRC treatment costs were based on publicly available data. The outcome measures included lifetime costs, number of cancers, cancer-related deaths, quality-adjusted life-years gained, and incremental cost-utility ratios. Sensitivity and scenario analyses were performed. Annual FIT, assuming mid-range testing characteristics, was more effective and less costly compared to all strategies (including no screening) except FIT-high. Among the lifetimes of 100,000 average-risk patients, the number of cancers could be reduced from 4,857 to 1,393 [corrected] and the number of CRC deaths from 1,782 [corrected] to 457, while saving CAN$68 per person. Although screening patients with FIT became more expensive than a strategy of no screening when the test performance of FIT was reduced, or the cost of managing CRC was lowered (e.g., for jurisdictions that do not fund expensive biologic chemotherapeutic regimens), CRC screening with FIT remained economically attractive.

CONCLUSIONS

CRC screening with FIT reduces the risk of CRC and CRC-related deaths, and lowers health care costs in comparison to no screening and to other existing screening strategies. Health policy decision makers should consider prioritizing funding for CRC screening using FIT.