Evelien Dekker

Academisch Medisch Centrum Universiteit van Amsterdam, Amsterdamo, North Holland, Netherlands

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Publications (263)1824.14 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Conventional adenomas were traditionally thought to be the only precursors to colorectal cancer (CRC). Nowadays, also serrated polyps are acknowledged as precursor lesions for CRC, responsible for up to 30% of all CRCs and probably a larger percentage of interval CRCs after colonoscopy. In recent years, much research is being done to unravel the serrated neoplasia pathway. Endoscopic detection of serrated polyps is still a challenge for gastroenterologists, which is illustrated by large variations in detection rates of serrated polyps in the proximal colon. Clinical practice is further inhibited by poor optical differentiation of SSA/Ps from conventional adenomas and HPs and difficult delineation of those lesions, resulting in incomplete resection. The main focus of this review is to highlight recent advancements in endoscopic imaging techniques with regards to detection, differentiation and resection of serrated polyps.
    Baillière&#x027 s Best Practice and Research in Clinical Gastroenterology 06/2015; DOI:10.1016/j.bpg.2015.05.009 · 3.28 Impact Factor
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    ABSTRACT: This study explored individuals' preferences for genetic testing for colorectal cancer (CRC) in a screening situation and their willingness to participate in genetic testing for Lynch syndrome, familial adenomatous polyposis (FAP), and familial colorectal cancer (FCC). For that purpose, 532 respondents aged 55-65 years completed a Discrete Choice Experiment. Using panel latent class models, the preferences for two screening situation characteristics (the probability of being genetically predisposed and the probability of developing CRC) and screening test characteristics (the frequency of preventive colonoscopies and CRC survival) were estimated. Based on these preferences, respondents' willingness to participate in the three screening initiatives was estimated. Lower-educated respondents and respondents who express serious anxiety and worries found colonoscopy frequency and the probability of developing CRC relatively more important and survival relatively less important compared with higher-educated respondents and respondents who express no anxiety and worries. These differences in preferences resulted in opposite preferences for participation in FCC and FAP screening. In conclusion, the general population is willing to participate in genetic screening for CRC. If individuals are suspected of genetic or familial CRC, they should at least be informed about their increased risk of being genetically predisposed and about the importance of participating in all preventive follow-up colonoscopies in order to maximize survival.European Journal of Human Genetics advance online publication, 3 June 2015; doi:10.1038/ejhg.2015.117.
    European journal of human genetics: EJHG 06/2015; DOI:10.1038/ejhg.2015.117 · 4.23 Impact Factor
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    ABSTRACT: Colorectal cancer (CRC) is considered a heterogeneous disease, both regarding pathogenesis and clinical behaviour. Four decades ago, the adenoma-carcinoma pathway was presented as the main pathway towards CRC, a conclusion that was largely based on evidence from observational morphological studies. This concept was later substantiated at the genomic level. Over the past decade, evidence has been generated for alternative routes in which CRC might develop, in particular the serrated neoplasia pathway. Providing indisputable evidence for the neoplastic potential of serrated polyps has been difficult. Reasons include the absence of reliable longitudinal observations on individual serrated lesions that progress to cancer, a shortage of available animal models for serrated lesions and challenging culture conditions when generating organoids of serrated lesions for in vitro studies. However, a growing body of circumstantial evidence has been accumulated, which indicates that ≥15% of CRCs might arise through the serrated neoplasia pathway. An even larger amount of post-colonoscopy colorectal carcinomas (carcinomas occurring within the surveillance interval after a complete colonoscopy) have been suggested to originate from serrated polyps. The aim of this Review is to assess the current status of the serrated neoplasia pathway in CRC and highlight clinical implications.
    Nature Reviews Gastroenterology &#38 Hepatology 05/2015; DOI:10.1038/nrgastro.2015.73 · 10.81 Impact Factor
  • Gastrointestinal Endoscopy 05/2015; 81(5):AB326-AB327. DOI:10.1016/j.gie.2015.03.1453 · 4.90 Impact Factor
  • Gastrointestinal Endoscopy 05/2015; 81(5):AB208. DOI:10.1016/j.gie.2015.03.193 · 4.90 Impact Factor
  • Gastrointestinal Endoscopy 05/2015; 81(5):AB145. DOI:10.1016/j.gie.2015.03.1231 · 4.90 Impact Factor
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    ABSTRACT: The adenoma detection rate (ADR) is the most important surrogate quality parameter for colorectal cancer (CRC) prevention. However, serrated polyps also are precursors of CRC. Large, prospective studies comparing the detection rate of serrated polyps among endoscopists in an era of awareness about the malignant potential of serrated polyps have not yet been performed. We aimed to compare the proximal serrated polyp (PSP) detection rate and the clinically relevant serrated polyp (RSP) detection rate among endoscopists and to analyze the association between these parameters and the ADR. Colonoscopy data were retrieved in one expert center between January 2011 and July 2014 by using a structured reporting system, enabling prospective and automatic quality assessment. Endoscopists who performed at least 50 colonoscopies within the timeframe were included for analysis. Multivariate logistic regression was used to compare the ADR, PSP detection rate, and RSP detection rate among endoscopists. The association among these parameters was calculated by using the Pearson r correlation coefficient. All lesions were assessed by an expert pathologist. In total, 16 endoscopists and 2088 colonoscopies were included for analysis. The PSP detection rate ranged from 2.9% to 18.6% (mean 10.4%) among endoscopists. Corrected for confounders, the odds ratio to detect ≥1 PSP, compared with endoscopists with the highest detection rate, ranged from 0.79 (95% confidence interval [CI], 0.41-1.52) to 0.12 (95% CI, 0.03-0.55). The PSP detection rate was highly correlated with the RSP detection rate (ρ 0.94; P < .001), ranging from 4.3% to 20.9% (mean 13.9%). The PSP detection rate moderately correlated with the ADR (0.55; P = .03), which ranged from 23.2% to 49.2% (mean 35.2%). The PSP detection rate is widely variable among endoscopists, strongly correlated with the RSP detection rate, and moderately correlated with the ADR. These results suggest a high miss rate of RSPs among endoscopists with low rates of PSP detection. Future research should determine the association between endoscopists' PSP detection rates and the risk of interval cancer. Copyright © 2015 American Society for Gastrointestinal Endoscopy. Published by Elsevier Inc. All rights reserved.
    Gastrointestinal endoscopy 04/2015; DOI:10.1016/j.gie.2015.02.044 · 4.90 Impact Factor
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    ABSTRACT: The effectiveness of colorectal cancer screening programs based on the fecal immunochemical test (FIT) is influenced by program adherence during consecutive screening rounds. We aimed to evaluate the participation rate, yield, and interval cancers in a third round of biennial CRC screening using FIT and to compare those with the first and the second screening round. A total of 3566 average-risk individuals aged 50-75 years were invited to participate in a third round of biennial FIT-based CRC screening. All FIT positives were recommended to undergo colonoscopy. We merged our data with the national cancer registry in the Netherlands to identify all non-screen-detected cancers in our cohort. Of the invitees, 2142 (60%) returned the FIT in this third screening round, compared to 56% in the second round and 57% in the first round. Overall, 153 of the third-round participants (7.1%) had a positive FIT result, versus 7.9% in the second round and 8.1% in the first round (P=0.05). Of all FIT positives, 123 (80%) underwent colonoscopy. Within this group, 33 persons had advanced neoplasia. The predictive value of FIT positivity for advanced neoplasia was 27% (33/123), compared to 42% in the second round and 54% in the first round - a significant decline (P<0.01). In an FIT-based screening program, participation rates remained stable over consecutive biennial screening rounds, while the FIT positivity rate and positive predictive value for advanced neoplasia gradually declined. Cancers in non-participants are significantly more advanced in staging than cancers in participants in the first round of screening. Copyright © 2015 Elsevier Ltd. All rights reserved.
    04/2015; 39(3). DOI:10.1016/j.canep.2015.03.012
  • Gastroenterology 04/2015; 148(4):S-757-S-758. DOI:10.1016/S0016-5085(15)32589-0 · 13.93 Impact Factor
  • Gastroenterology 04/2015; 148(4):S-757. DOI:10.1016/S0016-5085(15)32588-9 · 13.93 Impact Factor
  • Gastroenterology 04/2015; 148(4):S-112. DOI:10.1016/S0016-5085(15)30385-1 · 13.93 Impact Factor
  • Gastroenterology 04/2015; 148(4):S-160. DOI:10.1016/S0016-5085(15)30537-0 · 13.93 Impact Factor
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    ABSTRACT: We developed and validated an online questionnaire to document familial cancer history, in order to facilitate the detection of persons with a familial or hereditary colorectal cancer (CRC) risk. The development of the self-administered online questionnaire for the assessment of familial and hereditary CRC risk was based on nationwide criteria for referral to genetic specialists due to a Lynch syndrome suspicion, as well as existing criteria for surveillance colonoscopies because of an increased risk of familial CRC. The questionnaire was validated at a private colonoscopy center. Patients scheduled for colonoscopy were enrolled (n = 150). Performance of the questionnaire was assessed by comparing referrals based on questionnaire data against referral decisions based on full pedigree data. In a second validation phase, referrals based on questionnaire data were compared with referrals based on data collected in a telephone interview. We also calculated inter-observer agreement in referral decisions. In the first validation phase, the questionnaire had a sensitivity of 90 % (95 % CI 55-98 %) at a specificity of 98 % (95 % CI 87-100 %) in identifying persons qualifying for referral. In the second validation phase, sensitivity was 100 % (95 % CI 63-100) at a specificity of 97 % (95 % CI 91-99 %). In both validation phases an inter-observer agreement of 100 % in referral decisions was achieved. The online questionnaire has a high sensitivity and specificity in identifying persons qualifying for referral because of suspected Lynch syndrome or familial CRC. Implementation of this tool in colonoscopy clinics can facilitate the detection of patients with hereditary or familial CRC.
    Familial Cancer 03/2015; DOI:10.1007/s10689-015-9792-1 · 1.62 Impact Factor
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    ABSTRACT: The adenoma detection rate (ADR) is considered the most important quality indicator for colonoscopy and varies widely among colonoscopists. It is unknown whether the ADR of gastroenterology consultants can already be predicted during their colonoscopy training. To evaluate the ADR of fellows in gastroenterology and evaluate whether this predicts their ADR as gastroenterology consultant. Retrospective observational study. Academic and regional centers. Symptomatic patients undergoing colonoscopy. The variance in ADR among 7 gastroenterology fellows during their training (between May 2004 and March 2012) and of the same fellows after they registered as consultants (between October 2011 and April 2014) was evaluated. Multivariate logistic regression was performed to compare the highest detector (endoscopist with highest ADR) with the individual fellows and to evaluate whether an ADR of 20% or higher during the training was predictive of a high ADR as a consultant. During training, ADRs ranged from 14% to 36% (P < .001). Compared with the highest detector, the OR for detecting an adenoma ranged from 0.64 (95% CI, 0.40-1.03) to 0.29 (95% CI, 0.17-0.48). After registration, ADR ranged from 19.8% to 40.2% (P = .066). Compared with the highest detector during consultancy, the OR ranged from 0.64 (95% CI, 0.34-1.21) to 0.26 (95% CI, 0.13-0.52). Only 2 fellows significantly improved their ADR after completing their training. An ADR lower than 20% during training was associated with a lower ADR as a consultant (OR 0.51; 95% CI, 0.30-0.87). Retrospective study. Variance in ADR is already present during the endoscopy training of gastroenterology fellows. Most fellows do not improve their ADR after completing their training. These findings suggest that the ADR can be predicted during colonoscopy training, and we suggest that feedback and benchmarking should be implemented early during training of fellows in an effort to improve ADR in future daily practice as a consultant. Copyright © 2015 American Society for Gastrointestinal Endoscopy. Published by Elsevier Inc. All rights reserved.
    Gastrointestinal endoscopy 03/2015; DOI:10.1016/j.gie.2014.12.038 · 4.90 Impact Factor
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    ABSTRACT: During endoscopic surveillance in patients with longstanding colitis, a variety of lesions can be encountered. Differentiation between dysplastic and non-dysplastic lesions can be challenging. The accuracy of visual endoscopic differentiation and interobserver agreement (IOA) has never been objectified. We assessed the accuracy of expert and nonexpert endoscopists in differentiating (low-grade) dysplastic from non-dysplastic lesions and the IOA among and between them. An online questionnaire was constructed containing 30 cases including a short medical history and an endoscopic image of a lesion found during surveillance employing chromoendoscopy. A total of 17 endoscopists, 8 experts, and 9 nonexperts assessed all 30 cases. The overall sensitivity and specificity for correctly identifying dysplasia were 73.8% (95% confidence interval (CI) 62.1-85.4) and 53.8% (95% CI 42.6-64.7), respectively. Experts showed a sensitivity of 76.0% (95% CI 63.3-88.6) versus 71.8% (95% CI 58.5-85.1, p = 0.434) for nonexperts, the specificity 61.0% (95% CI 49.3-72.7) versus 47.1% (95% CI 34.6-59.5, p = 0.008). The overall IOA in differentiating between dysplastic and non-dysplastic lesions was fair 0.24 (95% CI 0.21-0.27); for experts 0.28 (95% CI 0.21-0.35) and for nonexperts 0.22 (95% CI 0.17-0.28). The overall IOA for differentiating between subtypes was fair 0.21 (95% CI 0.20-0.22); for experts 0.19 (95% CI 0.16-0.22) and nonexpert 0.23 (95% CI 0.20-0.26). In this image-based study, both expert and nonexpert endoscopists cannot reliably differentiate between dysplastic and non-dysplastic lesions. This emphasizes that all lesions encountered during colitis surveillance with a slight suspicion of containing dysplasia should be removed and sent for pathological assessment.
    Scandinavian Journal of Gastroenterology 03/2015; 50(8):1-7. DOI:10.3109/00365521.2015.1016449 · 2.33 Impact Factor
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    ABSTRACT: Accurate endoscopic differentiation would enable to resect and discard small and diminutive colonic lesions, thereby increasing cost-efficiency. Current classification systems based on narrow band imaging (NBI), however, do not include neoplastic sessile serrated adenomas/polyps (SSA/Ps). We aimed to develop and validate a new classification system for endoscopic differentiation of adenomas, hyperplastic polyps and SSA/Ps <10 mm. We developed the Workgroup serrAted polypS and Polyposis (WASP) classification, combining the NBI International Colorectal Endoscopic classification and criteria for differentiation of SSA/Ps in a stepwise approach. Ten consultant gastroenterologists predicted polyp histology, including levels of confidence, based on the endoscopic aspect of 45 polyps, before and after participation in training in the WASP classification. After 6 months, the same endoscopists predicted polyp histology of a new set of 50 polyps, with a ratio of lesions comparable to daily practice. The accuracy of optical diagnosis was 0.63 (95% CI 0.54 to 0.71) at baseline, which improved to 0.79 (95% CI 0.72 to 0.86, p<0.001) after training. For polyps diagnosed with high confidence the accuracy was 0.73 (95% CI 0.64 to 0.82), which improved to 0.87 (95% CI 0.80 to 0.95, p<0.01). The accuracy of optical diagnosis after 6 months was 0.76 (95% CI 0.72 to 0.80), increasing to 0.84 (95% CI 0.81 to 0.88) considering high confidence diagnosis. The combined negative predictive value with high confidence of diminutive neoplastic lesions (adenomas and SSA/Ps together) was 0.91 (95% CI 0.83 to 0.96). We developed and validated the first integrative classification method for endoscopic differentiation of small and diminutive adenomas, hyperplastic polyps and SSA/Ps. In a still image evaluation setting, introduction of the WASP classification significantly improved the accuracy of optical diagnosis overall as well as SSA/P in particular, which proved to be sustainable after 6 months. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.
    Gut 03/2015; 81(5). DOI:10.1136/gutjnl-2014-308411 · 13.32 Impact Factor
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    ABSTRACT: Several clinical trials have shown that colorectal cancer (CRC) screening can reduce cancer deaths. Its effectiveness is affected by the participation level. To develop targeted invitations, we need to understand why individual persons decide to participate. To evaluate reasons for participation among persons invited for faecal immunochemical test-based CRC screening, a total of 10 265 asymptomatic persons aged 50-75 years were invited to a Dutch CRC screening pilot (2008-2009). Reasons for participation were elicited by a questionnaire. A total of 3554 (66%) participants returned the questionnaire. Obtaining more certainty about the chances of developing cancer (ticked by 88%) and the occurrence of cancer in the family or the circle of acquaintances (18%) were the most frequently selected reasons for participation. We also explored reasons for nonparticipation among nonparticipants. In this subgroup, comorbidity and the absence of symptoms were the most frequently reported reasons for declining to participate, but the response rate was low. The vast majority of the participants decided to take up the screening because they wanted to know more about their chances of developing cancer.
    European journal of cancer prevention: the official journal of the European Cancer Prevention Organisation (ECP) 03/2015; 24(3). DOI:10.1097/CEJ.0000000000000139 · 2.76 Impact Factor
  • Gut 01/2015; 64(6). DOI:10.1136/gutjnl-2014-309020 · 13.32 Impact Factor
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    ABSTRACT: To determine adherence to recommended surveillance intervals in clinical practice. 2997 successive patients with a first adenoma diagnosis (57% male, mean age 59 years) from 10 hospitals, who underwent colonoscopy between 1998 and 2002, were identified via Pathologisch Anatomisch Landelijk Geautomatiseerd Archief: Dutch Pathology Registry. Their medical records were reviewed until 1 December 2008. Time to and findings at first surveillance colonoscopy were assessed. A surveillance colonoscopy occurring within ±3 months of a 1-year recommended interval and ±6 months of a recommended interval of 2 years or longer was considered appropriate. The analysis was stratified by period per change in guideline (before 2002: 2-3 years for patients with 1 adenoma, annually otherwise; in 2002: 6 years for 1-2 adenomas, 3 years otherwise). We also assessed differences in adenoma and colorectal cancer recurrence rates by surveillance timing. Surveillance was inappropriate in 76% and 89% of patients diagnosed before 2002 and in 2002, respectively. Patients eligible under the pre-2002 guideline mainly received surveillance too late or were absent (57% of cases). For patients eligible under the 2002 guideline surveillance occurred mainly too early (48%). The rate of advanced neoplasia at surveillance was higher in patients with delayed surveillance compared with those with too early or appropriate timed surveillance (8% vs 4-5%, p<0.01). There is much room for improving surveillance practice. Less than 25% of patients with adenoma receive appropriate surveillance. Such practice seriously hampers the effectiveness and efficiency of surveillance, as too early surveillance poses a considerable burden on available resources while delayed surveillance is associated with an increased rate of advanced adenoma and especially colorectal cancer. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.
    Gut 01/2015; DOI:10.1136/gutjnl-2013-306453 · 13.32 Impact Factor
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    ABSTRACT: Polyps of 1-5 mm are often detected during colonoscopy; these are only sporadically malignant. The removal, collection and pathological analysis of these polyps accounts for a significant part of the costs of a colonoscopy. The histologist's assessment is the gold standard and is endorsed in all guidelines for determination of the recommended interval for surveillance colonoscopy. If, however, it was possible to make a reliable endoscopic diagnosis of a polyp during colonoscopy the pathologist's assessment would not be needed. This strategy is known as optical diagnosis, and application would lead to cost-savings in the Netherlands. Before this strategy can be safely applied in practice minimal requirements for precision have to be met, and these are not fulfilled during use of white-light endoscopy. The development of electronic chromoendoscopy will lead to improved accuracy in endoscopic diagnosis of polyps.
    Nederlands tijdschrift voor geneeskunde 01/2015; 159:A8524.

Publication Stats

3k Citations
1,824.14 Total Impact Points


  • 2005–2015
    • Academisch Medisch Centrum Universiteit van Amsterdam
      • • Department of Gastroenterology and Hepatology
      • • Academic Medical Center
      Amsterdamo, North Holland, Netherlands
  • 2004–2015
    • University of Amsterdam
      • Department of Gastroenterology and Hepatology
      Amsterdamo, North Holland, Netherlands
  • 2012
    • Pontifical Catholic University of Chile
      CiudadSantiago, Santiago Metropolitan, Chile
    • VU University Medical Center
      • Department of Gastroenterology and Hepatology
      Amsterdamo, North Holland, Netherlands
    • Lyell McEwin Hospital
      Tarndarnya, South Australia, Australia