Number of Adenomas Removed and Colorectal Cancers Prevented in Randomized Trials of Flexible Sigmoidoscopy Screening

An efficient strategy for evaluating new non-invasive screening tests for colorectal cancer: the guiding principles

OBJECTIVE

New screening tests for colorectal cancer (CRC) are rapidly emerging. Conducting trials with mortality reduction as the end point supporting their adoption is challenging. We re-examined the principles underlying evaluation of new non-invasive tests in view of technological developments and identification of new biomarkers.

DESIGN

A formal consensus approach involving a multidisciplinary expert panel revised eight previously established principles.

RESULTS

Twelve newly stated principles emerged. Effectiveness of a new test can be evaluated by comparison with a proven comparator non-invasive test. The faecal immunochemical test is now considered the appropriate comparator, while colonoscopy remains the diagnostic standard. For a new test to be able to meet differing screening goals and regulatory requirements, flexibility to adjust its positivity threshold is desirable. A rigorous and efficient four-phased approach is proposed, commencing with small studies assessing the test's ability to discriminate between CRC and non-cancer states (phase I), followed by prospective estimation of accuracy across the continuum of neoplastic lesions in neoplasia-enriched populations (phase II). If these show promise, a provisional test positivity threshold is set before evaluation in typical screening populations. Phase III prospective studies determine single round intention-to-screen programme outcomes and confirm the test positivity threshold. Phase IV studies involve evaluation over repeated screening rounds with monitoring for missed lesions. Phases III and IV findings will provide the real-world data required to model test impact on CRC mortality and incidence.

CONCLUSION

New non-invasive tests can be efficiently evaluated by a rigorous phased comparative approach, generating data from unbiased populations that inform predictions of their health impact.

Impact of changes to the interscreening interval and faecal immunochemical test threshold in the national bowel cancer screening programme in England: results from the FIT pilot study

INTRODUCTION

The NHS Bowel Cancer Screening Programme (BCSP) faces endoscopy capacity challenges from the COVID-19 pandemic and plans to lower the screening starting age. This may necessitate modifying the interscreening interval or threshold.

METHODS

We analysed data from the English Faecal Immunochemical Testing (FIT) pilot, comprising 27,238 individuals aged 59-75, screened for colorectal cancer (CRC) using FIT. We estimated screening sensitivity to CRC, adenomas, advanced adenomas (AA) and mean sojourn time of each pathology by faecal haemoglobin (f-Hb) thresholds, then predicted the detection of these abnormalities by interscreening interval and f-Hb threshold.

RESULTS

Current 2-yearly screening with a f-Hb threshold of 120 μg/g was estimated to generate 16,092 colonoscopies, prevent 186 CRCs, detect 1142 CRCs, 7086 adenomas and 4259 AAs per 100,000 screened over 15 years. A higher threshold at 180 μg/g would reduce required colonoscopies to 11,500, prevent 131 CRCs, detect 1077 CRCs, 4961 adenomas and 3184 AAs. A longer interscreening interval of 3 years would reduce required colonoscopies to 10,283, prevent 126 and detect 909 CRCs, 4796 adenomas and 2986 AAs.

CONCLUSION

Increasing the f-Hb threshold was estimated to be more efficient than increasing the interscreening interval regarding overall colonoscopies per screen-benefited cancer. Increasing the interval was more efficient regarding colonoscopies per cancer prevented.

Higher Adenoma Detection Rates at Screening Associated With Lower Long-Term Colorectal Cancer Incidence and Mortality

BACKGROUND & AIMS

Detection and removal of adenomas reduces colorectal cancer (CRC) risk. The impact of adenoma detection rates (ADRs) on long-term CRC incidence and mortality is unknown. We investigated this using data from the UK Flexible Sigmoidoscopy Screening Trial.

METHODS

Of 167,882 UK Flexible Sigmoidoscopy Screening Trial participants, 40,085 were in the intervention arm and underwent flexible sigmoidoscopy screening at 13 trial centers. The median follow-up time was 17 years. At each center, 1 endoscopist performed most flexible sigmoidoscopies. Multivariable logistic regression was used to classify centers into high-, intermediate-, and low-detector groups based on their main endoscopist's ADR. We calculated the incidence and mortality of distal and all-site CRC, and estimated hazard ratios (HRs) with 95% CIs using Cox regression.

RESULTS

Five, 4, and 4 centers, respectively, were classified into the high-detector, intermediate-detector, and low-detector groups. The average ADRs in each respective group were 15%, 12%, and 9%. Distal CRC incidence and mortality were reduced among those screened compared with controls in all groups, and effects of screening varied significantly by detector ranking, with larger reductions in incidence and mortality seen in the high-detector group (incidence: HR, 0.34; 95% CI, 0.27-0.42; mortality: HR, 0.22, 95% CI, 0.13-0.37) than in the low-detector group (incidence: HR, 0.55; 95% CI, 0.44-0.68; mortality: HR, 0.54; 95% CI, 0.34-0.86). Similar results were observed for all-site CRC, with larger effects seen in the high-detector (incidence: HR, 0.58; 95% CI, 0.50-0.67; mortality: HR, 0.52; 95% CI, 0.39-0.69) than in the low-detector group (incidence: HR, 0.72; 95% CI, 0.61-0.85; mortality: HR, 0.68; 95% CI, 0.51-0.92), although the heterogeneity was not statistically significant.

CONCLUSIONS

Higher ADRs at screening provide greater long-term protection against CRC incidence and mortality. Isrctn.org, number: ISRCTN28352761.

Decreased colorectal cancer incidence and mortality in a diverse urban population with increased colonoscopy screening

Background

Although colorectal cancer screening has contributed to decreased incidence and mortality, disparities are present by race/ethnicity. The Citywide Colon Cancer Control Coalition (C5) and NYC Department of Health and Mental Hygiene (DOHMH) promoted screening colonoscopy from 2003 on, and hypothesized future reductions in CRC incidence, mortality and racial/ethnic disparities.

Methods

We assessed annual percent change (APC) in NYC CRC incidence, stage and mortality rates through 2016 in a longitudinal cross-sectional study of NY State Cancer Registry, NYC Vital Statistics, and NYC Community Health Survey (CHS) data. Linear regression tested associations between CRC mortality rates and risk factors.

Results

Overall CRC incidence rates from 2000 decreased 2.8% yearly from 54.1 to 37.3/100,000 population in 2016, and mortality rates from 2003 decreased 2.9% yearly from 21.0 to 13.9 in 2016 at similar rates for all racial/ethnic groups. Local stage disease decreased overall with a transient increase from 2002 to 2007. In 2016, CRC incidence was higher among Blacks (42.5 per 100,000) than Whites (38.0), Latinos (31.7) and Asians (30.0). In 2016, Blacks had higher mortality rates (17.9), than Whites (15.2), Latinos (10.4) and Asians (8.8). In 2016, colonoscopy rates among Blacks were 72.2%, Latinos 71.1%, Whites 67.2%, and Asians, 60.9%. CRC mortality rates varied by neighborhood and were independently associated with Black race, CRC risk factors and access to care.

Conclusions

In a diverse urban population, a citywide campaign to increase screening colonoscopy was associated with decreased incidence and mortality among all ethnic/racial groups. Higher CRC burden among the Black population demonstrate more interventions are needed to improve equity.

Improved detection of adenomas and sessile serrated polyps is maintained with continuous audit of colonoscopy

Background

The audit process may help improve performance indicators for colonoscopy quality but it is unclear whether this is sustained over several years.

Methods

44138 procedures for 28 endoscopists from 2004 to 2019 were analysed for polyp detection rate and withdrawal time. From 2012, 14 endoscopists were analysed with additional data on polyp histology and number of polyps removed.

Results

Polyp detection increased from 40.7% in 2004 to 62.2% in 2019; removal of polyps>1 cm remained constant (11%). Adenoma detection rate was 25.8% in 2012 and 28.3% in 2019. Sessile serrated polyp (SSP) detection rate increased from 4.5% to 14.7%; most of the increase was in the first 2 years of the histology part of the audit. There was a significant correlation of adenoma detection rate with mean number of adenomas (r=0.72, p=0.004) and a significant correlation of SSP detection with mean number of SSPs (r=0.85, p=0.0001).

Conclusion

The audit process appears to encourage a higher rate of polyp detection. This was due to increased detection of smaller polyps and increased detection of SSPs.

Aspects of colorectal cancer screening, methods, age and gender

Colorectal cancer (CRC) is, besides breast, prostate, lung and skin cancers, the most common cancer worldwide and is suitable for screening. The incidence of CRC varies considerably in different parts of the world: in well-developed countries, the incidence is between 30 and 70 per 100 000 inhabitants, whereas in less-developed countries such as sub-Saharan Africa, it is 10-20/100 000 inhabitants. Women have a lower incidence of CRC, which is usually one-third of total incidence. Several studies have shown that it is possible to decrease mortality from CRC with about 20%, which is evidenced through the data from countries with screening programmes. Though the method of choice to identify blood samples in faecal matter is under debate, the most feasible way is to perform colonoscopy. Other methods include more advanced faecal analyses, testing for mutations from CRC, sigmoidoscopy, CT colonoscopy or optical colonoscopy. Colonoscopy is in most countries not available in sufficient amount and has to be carried out with great accuracy; otherwise, lesions will be missed to identify, thus leading to complications. Gender is an issue in CRC screening, as women have about 20% fewer colorectal adenomas and CRCs, but they also have more right-sided lesions, which are more difficult to detect with tests for faecal blood since they create less blood in faeces. Thus, other strategies may have to be developed for women in order for screening to have the same effect. It is essential to introduce colorectal cancer screening in all countries together with other clinical pieces of advice such as information on smoking, obesity and exercise in order to reduce one of the most dangerous cancers.

Contribution of Surveillance Colonoscopy to Colorectal Cancer Prevention

BACKGROUND & AIMS

The contribution of surveillance colonoscopy, as opposed to that of initial colonoscopy examination, to prevention of colorectal cancer (CRC) is uncertain. We estimated the preventive effect of surveillance colonoscopy by applying the recently developed metric of adenoma dwell time avoided needed to prevent 1 CRC case (DTA).

METHODS

We followed subjects in the prostate, lung, colorectal and ovarian (PLCO) cancer screening trial who underwent colonoscopies following positive findings from sigmoidoscopies (colonoscopy cohort, n = 15,935) for CRC incidence for 10 years. The number and timing of adenomas removed during surveillance were measured in a subset (n = 3492) of patients and extrapolated to the entire cohort to estimate the total avoided adenoma dwell time. A previously determined DTA value of 612 dwell years was applied to estimate the number of CRC cases prevented by surveillance. Proportional reduction in CRC was computed as C_P/(C_O+C_P), where C_O and C_P are observed and estimated prevented cases, respectively.

RESULTS

In the colonoscopy cohort of the PLCO, 2882 subjects had advanced adenomas (AAs), 572 had 3 or more non-advanced adenomas (NAA₃₊), 4496 had 1-2 non-advanced adenomas (NAA_1-2), and 7985 had no adenoma (NA). The mean number of subsequent colonoscopy examinations over 10 years were 1.80 for subjects with AAs, 1.63 for subjects with NAA₃₊, and 1.46 for subjects with NAA_1-2. Average years of avoided adenoma dwell time per subject were 4.0 for subjects with AAs, 5.5 for subjects with NAA₃₊, and 2.4 for subjects with NAA_1-2. There were 56 cases of CRC in subjects with AAs, 4 cases of CRC in subjects with NAA₃₊, and 33 cases of CRC in subjects with NAA_1-2. Estimated proportional reductions in CRC incidence were 25.0% in subjects with AAs (95% CI, 16%-34%), 34.4% in subjects with NAA_1-2 (95% CI, 25%-40%), and 30.4% overall (in subjects with AAs, NAA₃₊, or NAA_1-2; 95% CI, 25%-40%). Absolute CRC incidence reductions were 7.1 per 10,000 PY in subjects with AAs and 4.1 per 10,000 PY in subjects with NAA_1-2.

CONCLUSIONS

Using the recently developed metric of DTA, we estimated that surveillance colonoscopy in the PLCO colonoscopy cohort during 10 years of follow up prevented 30% of CRC cases. Because the methodology for estimation is indirect, the true effect is uncertain.