Proportional incidence of interval colorectal cancer in a large population-based faecal immunochemical test screening programme

Bias due to coarsening of time intervals in the inference for the effectiveness of colorectal cancer screening

BACKGROUND

Observational studies are frequently used to estimate the comparative effectiveness of different colorectal cancer (CRC) screening methods due to the practical limitations and time needed to conduct large clinical trials. However, time-varying confounders, e.g. polyp detection in the last screening, can bias statistical results. Recently, generalized methods, or G-methods, have been used for the analysis of observational studies of CRC screening, given their ability to account for such time-varying confounders. Discretization, or the process of converting continuous functions into discrete counterparts, is required for G-methods when the treatment and outcomes are assessed at a continuous scale.

DEVELOPMENT

This paper evaluates the interplay between time-varying confounding and discretization, which can induce bias in assessing screening effectiveness. We investigate this bias in evaluating the effect of different CRC screening methods that differ from each other in typical screening frequency.

APPLICATION

First, using theory, we establish the direction of the bias. Then, we use simulations of hypothetical settings to study the bias magnitude for varying levels of discretization, frequency of screening and length of the study period. We develop a method to assess possible bias due to coarsening in simulated situations.

CONCLUSIONS

The proposed method can inform future studies of screening effectiveness, especially for CRC, by determining the choice of interval lengths where data are discretized to minimize bias due to coarsening while balancing computational costs.

Interval cancer after two rounds of a Swedish population-based screening program using gender-specific cut-off levels in fecal immunochemical test

OBJECTIVE

To evaluate interval cancer (IC) after two screening rounds of the Swedish population-based screening program of Stockholm-Gotland applying gender-specific cut-off levels in the fecal immunochemical test (FIT).

METHODS

All 60- to 69-year-olds invited to screening 2015-2019 were included. The cut-off level for a positive test was 40 µg/g in women and 80 µg/g in men. Screening-detected colorectal cancers (SD CRCs) and ICs were verified in the Swedish Colorectal Cancer Register, and the follow-up time was two years from invitation. The test sensitivity, the IC rate (ICs per 10,000 screening negatives) and the IC incidence (ICs per 100,000 person-years) relative to the background CRC incidence were assessed by gender and age. The FIT levels were compared in men and women for CRCs diagnosed within one year of the sample.

RESULTS

In the second screening round, 229,187 were invited, and SD CRCs and ICs were diagnosed in 193 and 144, respectively. The IC rate was 8.9 (7.4-10.3) and test sensitivity 0.61 (0.55-0.66), and was similar in men and women. For two screening rounds, the IC rate was significantly higher in men than in women, but the IC incidence/ background CRC incidence was similar in both genders. The FIT levels in female participants with CRC were significantly lower overall, and in early-staged CRCs as compared to men, and proximal localization was more common in women. In multivariable analysis, FIT levels were significantly lower in proximal CRCs.

CONCLUSION

Over two rounds, the IC incidence relative to the background CRC incidence was similar in men and women supporting a gender-specific screening strategy. The results could be explained by lower FIT levels in women due to proximal CRC localization.

Socioeconomic inequalities in interval colorectal cancer are explained by differences in faecal haemoglobin concentration and age: a register-based cohort study

OBJECTIVE

To estimate the risk of interval colorectal cancer (CRC) in faecal immunochemical test (FIT) negative screening participants according to socioeconomic status.

DESIGN

In this register-based study, first round FIT negative (<20 µg hb/g faeces) screening participants (biennial FIT, citizens aged 50-74) were followed to estimate interval CRC risk. Multivariate Cox proportional hazard regression models estimated HRs based on socioeconomic status defined by educational level and income. Models were adjusted for age, sex and FIT concentration.

RESULTS

We identified 829 (0.7‰) interval CRC in 1 160 902 individuals. Interval CRC was more common in lower socioeconomic strata with 0.7‰ for medium-long higher education compared with 1.0‰ for elementary school and 0.4‰ in the highest income quartile compared with 1.2‰ in the lowest. These differences did not translate into significant differences in HR in the multivariate analysis, as they were explained by FIT concentration and age. HR for interval CRC was 7.09 (95% CI) for FIT concentrations 11.9-19.8 µg hb/g faeces, and 3.37 (95% CI) for FIT between 7.2 and 11.8 compared with those <7.2. The HR rose with increasing age ranging from 2.06 (95% CI 1.45 to 2.93) to 7.60 (95% CI 5.63 to 10.25) compared with those under 55 years.

CONCLUSION

Interval CRC risk increased with decreasing income, heavily influenced by lower income individuals more often being older and having increased FIT concentrations. Individualising screening interval based on age and FIT result, may decrease interval CRC rates, reduce the social gradient and thereby increase the screening efficiency.

Impact of colorectal cancer screening on incidence, mortality and surgery rates: Evidences from programs based on the fecal immunochemical test in Italy

Fecal immunochemical tests (FIT) are among the most commonly used tests for colorectal cancer (CRC) screening programs worldwide. However, no randomised controlled trials have been carried out evaluating the impact of FIT-based screening programs (FIT-progr) on CRC incidence and mortality rates. Italian FIT-progr represent one of the most widespread and established experience worldwide. This paper reviews the evidence on the impact of FIT-progr on CRC incidence, tumor stage at diagnosis, mortality and surgery rates, deriving from Italian routine programs, i.e., outside the research setting. Unfortunately, the application of FIT-progr in Italy can be considered as an unplanned experimental model, due to the differences between Regions, both in health system management and adherence of the target population to the screening programs. The analysis of the manuscripts considered in the review, confirms that FIT-progr are effective in reducing CRC incidence and mortality rates and in improving the rate of endoscopic treatment of early invasive lesions. The review also highlights that FIT-progr are less performing for proximal colon than for distal colon and rectum.

Effects of Attendance to an Organized Fecal Immunochemical Test Screening Program on the Risk of Colorectal Cancer: An Observational Cohort Study

BACKGROUND & AIMS

This cohort study compared colorectal cancer (CRC) incidence and mortality between people who participated in an Italian regional biennial fecal immunochemical test (FIT) screening program and people who did not.

METHODS

The program started in 2005. The target population included over 1,000,000 people aged 50 to 69 years. The FIT was a one-sample OC-Sensor (Eiken Chemical Co, Tokyo, Japan) (cutoff, ≥20 μg hemoglobin/g feces). The average annual response rate to invitation was 51.4%. The records of people invited up to June 2016 were extracted from the screening data warehouse. Attenders were subjects who responded to the first 2 invitations or to the single invitation sent them before they became ineligible. Non-attenders were subjects who did not respond to any of these invitations. The records were linked with the regional CRC registry. People registered up to December 2016 were identified. Self-selection-adjusted incidence rate ratios (IRRs) and incidence-based CRC mortality rate ratios (MRRs) for attenders to non-attenders, with 95% confidence intervals (CIs), were calculated.

RESULTS

The cohort generated 2,622,131 man-years and 2,887,845 woman-years at risk with 4490 and 3309 CRC cases, respectively. The cohort of attenders was associated with an IRR of 0.65 (95% CI, 0.61-0.69) for men, 0.75 (95% CI, 0.70-0.80) for women and 0.69 (95% CI, 0.66-0.72) for both sexes combined. The self-selection-adjusted IRR was 0.67 (95% CI, 0.62-0.72) for men and 0.79 (95% CI, 0.72-0.88) for women. The IRR for stage I, II, III, and IV CRC was 1.35 (95% CI, 1.20-1.50), 0.61 (95% CI, 0.53-0.69), 0.60 (95% CI, 0.53-0.68) and 0.28 (95% CI, 0.24-0.32) for men and 1.64 (95% CI, 1.43-1.89), 0.60 (95% CI, 0.52-0.69), 0.73 (95% CI, 0.63-0.85) and 0.35 (95% CI, 0.30-0.42) for women. The overall incidence-based CRC MRR was 0.32 (95% CI, 0.28-0.37) for men, 0.40 (95% CI, 0.34-0.47) for women and 0.35 (95% CI, 0.31-0.39) for both sexes combined. The adjusted MRR was 0.35 (95% CI, 0.29-0.41) for men and 0.46 (95% CI, 0.37-0.58) for women.

CONCLUSIONS

Attendance to a FIT screening program is associated with a CRC incidence reduction of 33% among men and 21% among women, and a CRC mortality reduction of 65% and 54%, respectively.

How a faecal immunochemical test screening programme changes annual colorectal cancer incidence rates: an Italian intention-to-screen study

Background

This study aimed to evaluate the effectiveness of a biennial faecal immunochemical test (FIT) screening programme in reducing annual colorectal cancer (CRC) incidence in its dynamic target population.

Methods

The target population included over 1,000,000 persons aged 50–69 living in a region of northern Italy. The average annual response rate to invitation was 51.4%. Each observed annual age-standardised (Europe) rate per 100,000 persons between 2005, the year of introduction of the programme, and 2016 was compared with each expected annual rate as estimated with age-period-cohort (men) and age-period (women) models.

Results

For both sexes, the rates observed in 1997–2004 and those expected in 2005–2016 were stable. Observed rates increased in 2005, peaked in 2006 (the first full year of screening), dropped significantly below the expected level in 2009, and continued to decrease until 2013 (the eighth full year), after which no further significant changes occurred. In the pooled years 2013–2016, the observed incidence rate per 100,000 persons was 102.2 [95% CI: 97.4, 107.1] for men, 75.6 [95% CI: 71.6, 79.7] for women and 88.4 [95% CI: 85.3, 91.5] for both sexes combined, with an observed:expected incidence rate ratio of 0.68 [95% CI: 0.65, 0.71], 0.79 [95% CI: 0.76, 0.82] and 0.72 [95% CI: 0.66, 0.81], respectively.

Discussion

The study provided multiple consistent proofs of a causal relationship between the introduction of screening and a stable 28% decrease in annual CRC incidence after eight years.

Interval cancers in a population-based screening program for colorectal cancer with gender-specific cut-off levels for fecal immunochemical test

Objective

To evaluate interval cancers (IC) in the population-based Swedish regional colorectal cancer (CRC) screening program of Stockholm-Gotland, which uses gender-specific cut-off levels for the fecal immunochemical test (FIT).

Methods

All individuals aged 60–69 in Stockholm-Gotland invited to the screening program in October 2015 to September 2017 were followed up 2 years after invitation. Cut-off level for a positive FIT was 40 µg/g in women and 80 µg/g in men. Those with a positive FIT were referred to colonoscopy. Screening-detected CRC (SD-CRC) and IC after negative FIT (FIT-IC) or negative screening colonoscopy (Colonoscopy-IC) were identified in the Swedish colorectal cancer register. The IC rate was calculated as IC/(FIT negatives + negative screening colonoscopies). The IC incidence rate (ICs among negatives per 100,000 person-years) in different sex and age groups was compared to the mean CRC incidence before regional screening implementation. Test sensitivity was defined as SD-CRC/(SD-CRC + FIT-IC).

Results

Approximately 214,400 individuals were invited, and in 3521 screening colonoscopies 257(6.3%) SD-CRCs were detected. During follow-up, 124 FIT-IC and 7 Colonoscopy-IC were diagnosed, yielding an IC rate of 12.6 and 6.0 per 10,000 negatives (p = 0.00005) and a test sensitivity of 62% and 75% (p = 0.01) in men and women respectively. The IC incidence rate compared to CRC incidence was non-significantly lower in women.

Conclusion

In the population-based screening program of Stockholm-Gotland with a cut-off of 40 µg/g in women and 80 µg/g in men, the test sensitivity was higher and the IC rate was lower in women, which might imply lowering the cut-off level in men. However, the IC incidence rate relative to the CRC incidence was similar in both genders.

Significant decrease in interval colorectal cancer incidence after implementing immunochemical testing in a multiple-round guaiac-based screening programme

BACKGROUND AND AIMS

We aimed to evaluate the effects of switching to faecal immunochemical testing (FIT) on the cumulative 2-year incidence rate of interval cancers, interval cancer rate and test sensitivity within a mature population-based colorectal cancer screening programme consisting of six rounds of biennial guaiac faecal occult blood testing (gFOBT).

METHODS

The FIT results were compared with those of gFOBT used in each of the previous two rounds. For the three rounds analysed, 279,041 tests were performed by 156,186 individuals. Logistic regression analysis was used to determine interval cancer risk factors (Poisson regression) and to compare the sensitivity of FIT to gFOBT.

RESULTS

There were 612 cases of screen-detected cancers and 209 cases of interval cancers. The sex- and age-adjusted cumulative 2-year incidence rates of interval cancers were 55.7 (95% CI, 45.3-68.5), 42.4 (95% CI, 32.6-55.2) and 15.8 (95% CI, 10.9-22.8) per 100,000 person-years after the last two rounds of gFOBT and FIT, respectively. The FIT/gFOBT incidence rate ratio was 0.38 [95% CI, 0.27-0.54] (P < 0.001). Sex- and age-adjusted sensitivity was significantly higher with FIT than with gFOBT (OR = 6.70 [95% CI, 4.48-10.01], P < 0.0001).

CONCLUSIONS

This population-based study revealed a dramatic decrease in the cumulative incidence rates of interval cancers after switching from gFOBT to FIT. These data provide an additional incentive for countries still using gFOBT to switch to FIT.

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.

The Roadmap of Colorectal Cancer Screening

Colorectal cancer (CRC) is the third most common form of cancer in terms of incidence and the second in terms of mortality worldwide. CRC develops over several years, thus highlighting the importance of early diagnosis. National screening programs based on fecal occult blood tests and subsequent colonoscopy have reduced the incidence and mortality, however improvements are needed since the participation rate remains low and the tests present a high number of false positive results. This review provides an overview of the CRC screening globally and the state of the art in approaches aimed at improving accuracy and participation in CRC screening, also considering the need for gender and age differentiation. New fecal tests and biomarkers such as DNA methylation, mutation or integrity, proteins and microRNAs are explored, including recent investigations into fecal microbiota. Liquid biopsy approaches, involving novel biomarkers and panels, such as circulating mRNA, micro- and long-non-coding RNA, DNA, proteins and extracellular vesicles are discussed. The approaches reported are based on quantitative PCR methods that could be easily applied to routine screening, or arrays and sequencing assays that should be better exploited to describe and identify candidate biomarkers in blood samples.