Quantile-based fecal hemoglobin concentration for assessing colorectal neoplasms with 1,263,717 Taiwanese screenees

Interval cancer risk after the upper age limit of screening has been reached: Informing risk stratification in FIT-based colorectal cancer screening

Upper age limits are currently fixed for all fecal immunochemical test (FIT)-based colorectal cancer (CRC) screening programs. A risk-stratified upper age limit may be beneficial. Therefore, we assessed differences in interval CRC risk among individuals who had reached the upper age limit of screening (75 years). Individuals with a negative FIT (<47 μg Hb/g feces) in the final round of the Dutch CRC screening program were selected from the national screening database and linked to the national cancer registry to identify CRCs diagnosed within 24 months (interval CRCs). Survival analyses assessed whether sex and last fecal hemoglobin (f-Hb) concentration were associated with interval CRC risk. A multivariable logistic regression assessed whether sex, last f-Hb concentration and screening round were associated with stage distribution (early vs. late). Last f-Hb concentrations were considered detectable when they were >0 μg Hb/g feces. Among 305,761 individuals with a complete follow-up (24 months), 661 were diagnosed with interval CRC (21.6 per 10,000 negative FITs). Individuals with detectable f-Hb (15%) were 5 times more likely to be diagnosed with interval CRC than those without (HR 4.87, 95%CI: 4.19-5.65). Moreover, their cancers were more often detected at a late stage compared to individuals without detectable f-Hb (OR 1.45, 95%CI: 1.06-2.01). Our results show that interval CRC risk among individuals aged ≥75 differs substantially by last f-Hb concentration, indicating a uniform age to stop screening is suboptimal. Future research, taking into account multiple screening rounds and FIT results, should determine the optimal risk-stratified screening strategy.

Fecal Immunochemical Test Positivity Thresholds: An International Survey of Population-Based Screening Programs

BACKGROUND

The fecal immunochemical test for hemoglobin (FIT) is now a widely used non-invasive test in population-based organized screening programs for colorectal neoplasia. The positivity thresholds of tests currently in use are based on the fecal hemoglobin concentration (f-Hb), but the rationale for the adopted thresholds are not well documented. To understand current global usage of FIT in screening programs we conducted an international survey of the brands of FIT used, the f-Hb positivity threshold applied and the rationale for the choice.

METHODS

All members of the World Endoscopy Organization CRC Screening Committee were invited to complete an eight-element initial electronic survey exploring the key aims. Responses were obtained from 63 individuals, representing 38 specific locations in 28 countries. A follow-up survey on technical issues was offered to the 38 locations, with replies from 17 sites in 13 countries.

RESULTS

In-use quantitative FIT were provided by four main manufacturers; Minaris Medical (2 countries), Eiken Chemical Company/Polymedco (21), Alfresa Pharma (2) and Sentinel Diagnostics (4). Of the 38 screening sites, 15 used the threshold of 20 µg hemoglobin/g feces, while thresholds ranged between 8.5 and 120 ug/g in the remainder. Seven explanations were given for adopted FIT thresholds; maximizing the sensitivity for colorectal neoplasia (n = 23) was the most common followed by the availability of colonoscopy resources (n = 18). Predictive value, specificity, and cost effectiveness were less frequently reported as the rationale. Nine sites found it necessary to change the threshold that they had initially selected.

CONCLUSIONS

This international survey has documented the wide range of FIT positivity thresholds that are in current use. Quantitative FITs enable programs to achieve the desired program outcomes within available resource constraints by adjusting the positivity threshold. This supports the need for enabling positivity threshold adjustment of emerging new screening tests based on novel predictive biomarkers, rather than providing inflexible test endpoints.

Harm-to-Benefit Ratio of Fecal Immunochemical Test-Based Screening for Colorectal Cancer Given Prior Fecal Hemoglobin Concentrations

BACKGROUND AND AIMS

This study aimed to provide evidence on the harm-to-benefit ratio of fecal immunochemical test (FIT)-based colorectal cancer (CRC) screening by previous fecal hemoglobin (f-Hb) concentrations, as reflected in the number needed to screen (NNS) and number needed to scope (NNSc).

METHODS

Participants in up to 4 FIT screening rounds of the Dutch CRC screening program were included. The main outcomes of this study were the NNS and NNSc to detect 1 CRC and/or advanced neoplasia (AN) in screening rounds 2, 3, or 4, conditional on previous f-Hb concentrations. Outcomes were compared between participants using chi-square tests and logistic regression.

RESULTS

In total, 2,428,883 study participants completed at least 2 consecutive FITs, 1,308,684 completed 3 FITs, and 150,958 completed 4 FITs. There were 31,400, 16,060, and 2007 ANs detected by round, respectively. The NNS for individuals with vs without a history of detectable f-Hb differed significantly irrespective of screening round. Individuals without detectable f-Hb in previous negative FITs had almost 9 times the NNS to detect 1 AN compared with those with detectable f-Hb (odds ratio, 8.71; 95% confidence interval, 8.51-8.92). A similar directional pattern was observed for NNSc, although the differences were smaller (odds ratio, 2.7; 95% confidence interval, 2.7-2.8).

CONCLUSIONS

The harm-to-benefit ratio of FIT-based screening is substantially greater in individuals without vs with prior detectable f-Hb. Less intensive screening should be considered for this lower-risk group.

An Adjustable Positivity Threshold for Non-invasive Screening Tests for Colorectal Neoplasms Can Improve Screening Program Effectiveness and Feasibility

BACKGROUND

In two-step population screening for colorectal cancer (CRC), a simple non-invasive test, commonly a fecal immunochemical test for hemoglobin (FIT), is first undertaken to predict, based on the fecal hemoglobin concentration (f-Hb), who is more likely to have colorectal neoplasia and needs colonoscopy.

AIM

To evaluate the importance of being able to adjust the f-Hb threshold that triggers follow-up colonoscopy (the "positivity threshold"), we evaluated the predictive value of f-Hb for colorectal neoplasia and its implications for the configuration of new non-invasive tests.

METHODS

A literature review was conducted on the use of quantitative FIT to select the positivity threshold, followed by using f-Hb from a large population to model how adjusting the positivity threshold enabled achievement of the desired program outcomes in a feasible manner.

RESULTS

The literature review and the modeling found that while the f-Hb positivity threshold is predictive for colorectal neoplasia across a wide range of f-Hb, there is a complex relationship between program outcomes and f-Hb. The threshold determines not just clinical accuracy (including true- and false-positive results for CRC and/or advanced precursor lesions), but also the colonoscopy workload. A lower f-Hb threshold is associated with a higher sensitivity for neoplasia but a lower specificity and a heavier load of follow-up colonoscopies. Consequently, the threshold determines a program's impact on population CRC mortality and incidence, but also its feasibility and cost-effectiveness within a health-care system.

DISCUSSION

We are entering a new era of non-invasive screening tests, where multiple biomarkers found in biological samples such as blood as well as feces, are being developed and evaluated. These typically specify a non-transparent algorithm, developed with machine learning, to provide a predictive dichotomous positive/negative result with a fixed associated clinical accuracy and colonoscopy workload. This will restrict use of new tests in jurisdictions where the accuracy and workload implications do not match the desired screening program outcomes.

CONCLUSION

However, similar to flexible FIT positivity thresholds, it would be ideal if new tests also provide capacity for screening program providers to select the positivity threshold that delivers their desired screening outcomes in a feasible manner. How marketing, distribution and reimbursement of non-invasive tests are approved, funded and implemented varies widely across jurisdictions and must be taken into account.

Risk-stratified strategies in population screening for colorectal cancer

Colorectal cancer (CRC) screening has been demonstrated to reduce CRC incidence and mortality. However, besides such benefits, CRC screening is also associated with potential harmful effects. In an ideal world, screening would only be directed to the small proportion of the population that might potentially benefit. Risk‐based screening can be seen as a first step towards this ideal world, by redistributing screening resources from low‐risk to high‐risk individuals. In theory, this should result in scarce resources being used in individuals who benefit most, while intensity of screening is reduced in individuals who benefit less, hence improving the benefit‐harm ratio among all invitees. Available strategies that have been proposed for risk‐based CRC screening include using information on age, sex, prior screening history, lifestyle and/or genetic information. Implementation of risk‐based screening requires careful consideration of reliable risk prediction models, participation with screening and informed decision‐making. While it is important to recognise the limitations of current approaches, available evidence suggests that it might be feasible to start planning the introduction of tailored strategies within screening programmes. Implementing risk‐based screening based on age, sex and prior screening history alone would already represent a substantial improvement over current uniform screening approaches. We propose that it is time that screening programmes start there and continue striving towards more comprehensive approaches embedding primary prevention as an effective approach to lower risk for everyone.

The Synthetic Myeloperoxidase Inhibitor AZD3241 Ameliorates Dextran Sodium Sulfate Stimulated Experimental Colitis

Chronic inflammatory bowel disease (IBD) is a condition with multifactorial pathophysiology. To date, there is no permanent cure and the disease is primarily managed by immunosuppressive drugs; long-term use promotes serious side effects including increased risk malignancies. The current study aimed to target neutrophil-myeloperoxidase, a key contributor to the pathogenesis of IBD, through the use of AZD3241that inhibits extracellular myeloperoxidase. Experimental colitis was induced in C57BL/6 male mice by 2% dextran sodium sulfate in drinking water ad libitum over 9 days. Mice received either normal drinking water and peanut butter (control), 2% DSS in drinking water and peanut butter or 2% DSS in drinking water and AZD3241 (30 mg/kg) dispersed in peanut butter daily for 9 days. Administered AZD3241 attenuated body weight loss (10% p<0.05) and improved clinical score (9 fold p<0.05; a score comprising the time-dependent assessment of stool consistency and extent of rectal bleeding), loss of colonic crypts (p<0.001), preserved surface epithelium (p<0.001) and enhanced expression of the transcription factor Nrf-2 (regulator of antioxidants) and enhanced expression of the downstream antioxidant response element haeoxygenase-1 (HO-1) in the colon tissue. Also, the concentration of fecal hemoglobin and the myeloperoxidase specific oxidative damage biomarker 3-chlorotyrosine in the colon were significantly decreased in the presence of AZD3241. This latter result was consistent with AZD3241 inhibiting MPO activity in vitro. Overall, AZD3241 ameliorated the course and severity of experimental colitis through ameliorating MPO derived tissue damage and could be considered a potential therapeutic option, subject to further validation in chronic IBD models.