Aberrantly Methylated Gene Marker Levels in Stool: Effects of Demographic, Exposure, Body Mass, and Other Patient Characteristics

Abstract

Introduction Stool DNA testing has emerged as a patient-friendly, noninvasive, and easily distributable new approach to colorectal cancer (CRC) screening that achieves high detection rates of both CRC and clinically significant precancerous lesions [1,2]. Incorporating key advances, including next generation analytical technology and broadly informative marker panels, prototype stool DNA tests in recent case-control studies have yielded sensitivities for curable stage CRC of 87-98% and for adenomas >1 cm of 64% and higher with increasing size at specificity cutoff ≥ 90% [3-5]. An understanding of factors that contribute to non-specificity is critical to optimizing test configuration and clinical use of this screening approach. Yet, relatively little has been reported about the effects of common clinical variables on stool DNA marker levels. This is particularly true of aberrantly methylated gene markers which, to date, have proven to be the most informative panel elements in prototype stool DNA tests [3-5]. Aberrant methylation of the promoter region of numerous genes occurs early during colorectal carcinogenesis [6-10]. While there exists remarkable molecular heterogeneity across colorectal neoplasms, we [3,10,11] and others [7,9,12,13] have found that several aberrantly methylated gene markers alone or in combination almost perfectly discriminate CRC and adenomas from normal colorectal mucosa at the tissue level. However, many of these candidate markers fail on stool application due to non-specificity resulting from high marker background levels [3,10]. In a recent large study [3], we selected four methylated gene markers (BMP3, NDRG4, vimentin, and TFPI2) that maintained both high sensitivity and high specificity for detection of CRC and advanced adenomas on stool testing. The effects of common clinical covariates on these 4 candidate methylation markers have not been evaluated. Based on observations across different tissues, rates of aberrant methylation of some genes may be affected by various non-neoplastic factors. Such factors may include demographic variation, particularly age [14], exposures such as smoking [15], alcohol intake [15,16], or analgesic use [17], and body mass [18] or diabetes mellitus [19]. Furthermore, aberrant methylation on some genes has been detected in histologically normal mucosa at points distant from colorectal neoplasms [20] and such molecular field defects could conceivably contribute to non-specificity on stool testing. Abstract Background: Selected aberrantly methylated genes represent sensitive candidate stool markers for colorectal cancer (CRC) screening. We assessed the impact of demographic, exposure, body mass, and other patient variables on stool levels of highly informative methylated gene markers-BMP3, NDRG4, vimentin, and TFPI2.

Stool Methylated DNA Markers Decrease Following Colorectal Cancer Resection—Implications for Surveillance

“…Third, the experimental design assumes that stool DNA markers remain constant in normal controls over time. While stool methylation markers may increase slightly with age [12], we did not adjust pre- and postoperative comparisons given the relatively short period of time between collections (6–46 months). While the patient population was largely non-Hispanic whites, we have previously shown that levels of methylated DNA markers in stools do not appear to be affected by race [12].…”

Multi-Target Stool DNA Test: A New High Bar for Noninvasive Screening

“…Based on covariate analyses of MT-sDNA positivity among those with normal colonoscopy [4,41], only age appears to significantly influence DNA marker levels in stool. The progressive rise in stool marker levels with age over 65 may relate to increase in polyp burden or accumulated field changes.…”

Long-term Follow-up of Patients Having False-Positive Multitarget Stool DNA Tests after Negative Screening Colonoscopy: The LONG-HAUL Cohort Study

“…Study 1 (“Specificity”) cross-sectionally sampled asymptomatic patients at average risk for CRC between February 2010 and August 2010 (21). Study 2 (“Cutoff”) was a case-control sampling of higher-risk patients referred for known colorectal neoplasia and asymptomatic average-risk control patients who were scheduled for screening at the time of study enrollment, between August 2011 and December 2011 (11).…”

“…(20). As such, we aimed to address this question by examining long-term outcomes among participants from three pre-approval studies of MT-sDNA (9, 11, 21) who had either non-advanced adenomas only or negative findings on baseline colonoscopy. We measured differences in mortality rate, subsequent cancer incidence, and development of alarm symptoms among patients with apparent FP and true negative (TN) MT-sDNA results.…”