Circulating nucleosomes for detection of colorectal cancer and high-risk advanced adenomas.

Abstract

169 Background: Detection and treatment of early colorectal cancer (CRC) or advanced adenomas (AA) is the key for superior outcomes and fecal immunochemical testing (FIT)-based screening has proven effective in reducing CRC death and the risk of advanced-stage CRC but the discrepancy in the effectiveness was observed between proximal and distal cancers. On the other hand, false-positive results of FIT with 60 % of negative colonoscopy is another concern, considering the burden to the screening participants and the healthcare providers. A blood-based test as an alternative or supplement to FIT has the potential to concurrently enhance the detection of high-risk neoplasms and identify individuals at risk who should then be referred to colonoscopy. We investigated the levels of circulating free nucleosomes containing different epigenetic modifications in patients referred for colonoscopy. Methods: 10mls whole blood was obtained from 520 asymptomatic patients prior to colonoscopy at National Taiwan University Hospital. Patients were classified into 5 groups based on their colonoscopy reports: (i) patient with CRC (n = 33), (ii) patients with AA (n = 123, including 18 with AA > 2cm); (iii) patients with non-AA (n = 168); (iv) patients with non-neoplastic polyps (n = 30); (vi) healthy controls with no endoscopic lesion (n = 166). Plasma samples were analyzed for nucleosome levels using 7 different quantitative immunoassays (Nu.Q assays; Belgian Volition SRL, Belgium) targeting H3.1-nucleosomes or different histone modifications (H3K27Me3-, H3K36Me3-, H3K9Me3-, H3K14Ac-, H3K27Ac- or H3R8Cit-nucleosomes). All study subjects were asked to collect a stool sample at home within 48-hours before the colonoscopy. The fecal samples were assayed with the Eiken OC-SENSOR FIT kit (Eiken Chemical Co., Ltd., Tokyo, Japan) for all study subjects. Results: At a cut-off of 20µg/g feces, the FIT test showed a sensitivity of 92,9% at 17.5% specificity for CRC +AA vs. Controls. All the CRC patients and 83.3% of the high-risk AA (> 2cm) patients were FIT positive. A combination of 2 Nu.Q biomarkers: H3K27Me3 and H3R8Cit with FIT in a logistic regression model showed improved sensitivity of 95% at 20.6% specificity allowing the detection of all CRC patients and 94.3% of AA patients including all the high-risk adenomas. The FIT test detected 46 out of 55 proximal adenomas whereas the combined model could detect 50 proximal adenomas including 3 proximal AA > 2cm not being detected by FIT (p < 0.05). The same combination would reduce unnecessary colonoscopies by 21.8% of the control and 23.3% of the non-neoplastic polyps subgroups compared to 17.5% and 6.7%, respectively with the FIT test alone. Conclusions: Our results indicate that H3K27Me3 and H3R8Cit-nucleosome levels in combination with FIT could improve the detection of proximal high-risk AA and could also provide a non-invasive method to reduce unnecessary colonoscopy.