Novel Stool-Based Protein Biomarkers for Improved Colorectal Cancer Screening: A Case-Control Study

BACKGROUND

The fecal immunochemical test (FIT) for detecting hemoglobin is used widely for noninvasive colorectal cancer (CRC) screening, but its sensitivity leaves room for improvement.

OBJECTIVE

To identify novel protein biomarkers in stool that outperform or complement hemoglobin in detecting CRC and advanced adenomas.

DESIGN

Case-control study.

SETTING

Colonoscopy-controlled referral population from several centers.

PARTICIPANTS

315 stool samples from one series of 12 patients with CRC and 10 persons without colorectal neoplasia (control samples) and a second series of 81 patients with CRC, 40 with advanced adenomas, and 43 with nonadvanced adenomas, as well as 129 persons without colorectal neoplasia (control samples); 72 FIT samples from a third independent series of 14 patients with CRC, 16 with advanced adenomas, and 18 with nonadvanced adenomas, as well as 24 persons without colorectal neoplasia (control samples).

MEASUREMENTS

Stool samples were analyzed by mass spectrometry. Classification and regression tree (CART) analysis and logistic regression analyses were performed to identify protein combinations that differentiated CRC or advanced adenoma from control samples. Antibody-based assays for 4 selected proteins were done on FIT samples.

RESULTS

In total, 834 human proteins were identified, 29 of which were statistically significantly enriched in CRC versus control stool samples in both series. Combinations of 4 proteins reached sensitivities of 80% and 45% for detecting CRC and advanced adenomas, respectively, at 95% specificity, which was higher than that of hemoglobin alone (P < 0.001 and P = 0.003, respectively). Selected proteins could be measured in small sample volumes used in FIT-based screening programs and discriminated between CRC and control samples (P < 0.001).

LIMITATION

Lack of availability of antibodies prohibited validation of the top protein combinations in FIT samples.

CONCLUSION

Mass spectrometry of stool samples identified novel candidate protein biomarkers for CRC screening. Several protein combinations outperformed hemoglobin in discriminating CRC or advanced adenoma from control samples. Proof of concept that such proteins can be detected with antibody-based assays in small sample volumes indicates the potential of these biomarkers to be applied in population screening.

PRIMARY FUNDING SOURCE

Center for Translational Molecular Medicine, International Translational Cancer Research Dream Team, Stand Up to Cancer (American Association for Cancer Research and the Dutch Cancer Society), Dutch Digestive Foundation, and VU University Medical Center.

Abstract 3176: Improved colorectal cancer screening by new stool-based protein markers

Background

The fecal immunochemical test (FIT) is used in many countries for non-invasive screening for colorectal cancer (CRC), but its characteristics leave room for improvement. We aimed to identify novel stool-based protein markers in stool that outperform or complement hemoglobin in detecting CRC.

Materials and methods

A series of large scale proteomic discovery and validation was conducted on a total of 313 human stool specimens. A discovery set consisted of 22 stool specimens (12 CRC and 10 controls), and isolated proteins were analyzed by an in-dept mass spectrometry GeLC-MS/MS workflow. An external validation set consisted of 291 independent stool specimens (79 CRC, 40 advanced adenoma (AA), 43 nonadvanced adenoma (A) and 129 controls), and isolated proteins were analyzed by single-shot mass spectrometry (Q-Exactive). As proof of concept, commercially available meso scale discovery (MSD) assays were performed on an independent validation set of 72 FIT fluid samples set including 14 CRC, 16 AA, 18 A and 24 controls.

Results

Of the 468 human proteins quantified in the discovery set, 93 were significantly enriched in CRC vs controls (p&lt;0.05). Of these, 29 were significantly found enriched in CRC vs controls in the validation set (q&lt;0.05). CART analysis and exhaustive search revealed a combination of 4 proteins as the most optimal combination to differentiate CRC from controls. A logistic regression model of this combination of proteins detected CRC with a sensitivity of 73% as compared to 43% for hemoglobin (HBA1) alone at a fixed specificity of 95% (p = 0.00003). Another combination of 4 proteins was the most optimal combination to differentiate AA from controls, which showed a sensitivity of 48% vs 8% for hemoglobin (p = 0.0002) at fixed specificity of 95%. Evaluation of one of the markers on FIT fluid samples provided proof of concept that these proteins can be detected in FIT fluid and can significantly discriminate CRC from healthy controls (p &lt; 0.001).

Conclusion

Proteome profiling on stool samples revealed 29 validated proteins significantly enriched in CRC samples compared to controls. A panel of 4 complementary protein markers outperformed hemoglobin for detection of CRC as well as AA. Proof of concept for detecting the proteins in FIT fluids confirmed the high potential of these markers for screening purposes in a non-invasive and cost-effective manner.

Citation Format: Linda J. Bosch, Meike De Wit, Annemieke C. Hiemstra, Sander R. Piersma, Thang V. Pham, Gideon Oudgenoeg, Veerle Coupe, George Scheffer, Sandra Mongera, Jochim Terhaar Sive droste, Frank Oort, Sietze van Turenhout, Ilhame Ben Larbi, Chris Mulder, Beatriz Carvalho, Remond JA Fijneman, Connie R. Jimenez, Gerrit A. Meijer. Improved colorectal cancer screening by new stool-based protein markers. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3176.

Abstract 1563: Stool proteomics reveals novel candidate biomarkers for colorectal cancer screening

Introduction and objectives: Early detection of colorectal cancer (CRC) and its precursor lesions is an effective approach to reduce CRC mortality rates. The fecal immunochemical test (FIT) is a non-invasive CRC screening test that detects small traces of the blood protein hemoglobin. Although beneficial in its current form, the FIT test characteristics leave room for improvement. The aim of the present study was to identify and validate novel protein biomarkers in stool that complement or outperform the current hemoglobin-based test, to improve its diagnostic accuracy.

Methods: Proteins isolated from stool from 10 subjects without any signs of colorectal neoplasia (controls) at colonoscopy and from 12 CRC patients were analyzed by GeLC-MS/MS (discovery set). Data were analyzed by comparing protein abundancies, measured as spectral counts. Analysis of differential proteins was performed using the beta-binomial test. Findings were validated by mass spectrometry (Q-Exactive) in an independent series of 292 stool samples obtained from control subjects (n = 109) and subjects with adenomas (n = 55), advanced adenomas (n = 53), or CRCs (n = 75).

Results and Discussion: In total 830 human proteins were identified in the discovery set, of which 134 were significantly enriched in CRC. These included 78 proteins that were significantly more enriched in FIT-negative CRC stool samples compared to controls. Preliminary analysis of the validation set indicates that more than half of these markers are significantly more abundant in CRC samples compared to controls.

Conclusion: Proteome profiling of stool samples revealed novel candidate biomarkers to improve current CRC screening tests. More data analysis is currently ongoing to select most promising protein biomarkers for clinical assay development.

Citation Format: Linda JW Bosch, Meike de Wit, Annemieke C. Hiemstra, Sander Piersma, Thang Pham, Gideon Oudgenoeg, George Scheffer, Sandra Mongera, Malgorzata Komor, Jochim Terhaar Sive Droste, Frank A. Oort, Sietze van Turenhout, Ilhame Ben Larbi, Chris JJ Mulder, Beatriz Carvalho, Remond JA Fijneman, Connie Jimenez, Gerrit A. Meijer. Stool proteomics reveals novel candidate biomarkers for colorectal cancer screening. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1563. doi:10.1158/1538-7445.AM2015-1563

The scent of colorectal cancer: detection by volatile organic compound analysis

The overall metabolic state of an individual is reflected by emitted volatile organic compounds (VOCs), which are gaseous carbon-based chemicals. In this review, we will describe the potential of VOCs as fully noninvasive markers for the detection of neoplastic lesions of the colon. VOCs are detected by our sensory olfactory nerves and form the molecular basis for our sense of smell. As such, we emit our own individual odor fingerprint or so-called smellprint. This may change over time in response to any alteration in metabolism such as modifications caused by gastrointestinal infection, inflammation, external factors such as medication and diet, or development of neoplastic disease such as colorectal cancer. This means that analysis of VOCs can provide a fully noninvasive metabolomics biomarker profile that could be used as a diagnostic tool. Thus far, canine scent detection, gas chromatography-mass spectrometry, and electronic nose technologies allow for discrimination between patients with and without colorectal cancer and also its precursor (advanced adenoma) with promising accuracy. The challenge for future research is to identify specific biomarkers driving these signals. This enables the development of primed sensors tailored toward accurate identification of volatiles specific to colorectal cancer and adenomas. Such a technique may allow noninvasive monitoring of response to therapy and could revolutionize screening practices for colorectal cancer and potentially many other gastrointestinal diseases.

Higher fecal immunochemical test cutoff levels: lower positivity rates but still acceptable detection rates for early-stage colorectal cancers

BACKGROUND

Adjusting the threshold for positivity of quantitative fecal immunochemical tests (FIT) allows for controlling the number of follow-up colonoscopies in a screening program. However, it is unknown to what extent higher cutoff levels affect detection rates of screen-relevant neoplasia. This study aimed to assess the effect of higher cutoff levels of a quantitative FIT on test positivity rate and detection rate of early-stage colorectal cancers (CRC).

METHODS

Subjects above 40 years old scheduled for colonoscopy in 5 hospitals were asked to sample a single FIT (OC sensor) before colonoscopy. Screen-relevant neoplasia were defined as advanced adenoma or early-stage cancer (stage I and II). Positivity rate, sensitivity, and specificity were evaluated at increasing cutoff levels of 50 to 200 ng/mL.

RESULTS

In 2,145 individuals who underwent total colonoscopy, 79 patients were diagnosed with CRC, 38 of which were with early-stage disease. Advanced adenomas were found in 236 patients. When varying cutoff levels from ≥ 50 to ≥ 200 ng/mL, positivity rates ranged from 16.5% to 10.2%. With increasing cutoff levels, sensitivity for early-stage CRCs and for screen-relevant neoplasia ranged from 84.2% to 78.9% and 47.1% to 37.2%, respectively.

CONCLUSIONS

Higher FIT cutoff levels substantially decrease test positivity rates with only limited effects on detection rates of early-stage CRCs. However, spectrum bias resulting in higher estimates of sensitivity than would be expected in a screening population may be present.

IMPACT

Higher cutoff levels can reduce strain on colonoscopy capacity with only a modest decrease in sensitivity for curable cancers.