Lipidomic Profiling of Colorectal Lesions for Real-Time Tissue Recognition and Risk-Stratification Using Rapid Evaporative Ionization Mass Spectrometry

OBJECTIVE

Rapid evaporative ionization mass spectrometry (REIMS) is a metabolomic technique analyzing tissue metabolites, which can be applied intraoperatively in real-time. The objective of this study was to profile the lipid composition of colorectal tissues using REIMS, assessing its accuracy for real-time tissue recognition and risk-stratification.

SUMMARY BACKGROUND DATA

Metabolic dysregulation is a hallmark feature of carcinogenesis; however, it remains unknown if this can be leveraged for real-time clinical applications in colorectal disease.

METHODS

Patients undergoing colorectal resection were included, with carcinoma, adenoma and paired-normal mucosa sampled. Ex vivo analysis with REIMS was conducted using monopolar diathermy, with the aerosol aspirated into a Xevo G2S QToF mass spectrometer. Negatively charged ions over 600 to 1000 m/z were used for univariate and multivariate functions including linear discriminant analysis.

RESULTS

A total of 161 patients were included, generating 1013 spectra. Unique lipidomic profiles exist for each tissue type, with REIMS differentiating samples of carcinoma, adenoma, and normal mucosa with 93.1% accuracy and 96.1% negative predictive value for carcinoma. Neoplasia (carcinoma or adenoma) could be predicted with 96.0% accuracy and 91.8% negative predictive value. Adenomas can be risk-stratified by grade of dysplasia with 93.5% accuracy, but not histological subtype. The structure of 61 lipid metabolites was identified, revealing that during colorectal carcinogenesis there is progressive increase in relative abundance of phosphatidylglycerols, sphingomyelins, and mono-unsaturated fatty acid-containing phospholipids.

CONCLUSIONS

The colorectal lipidome can be sampled by REIMS and leveraged for accurate real-time tissue recognition, in addition to riskstratification of colorectal adenomas. Unique lipidomic features associated with carcinogenesis are described.

Validation of Ultrasonic Harmonic Scalpel for Real-Time Tissue Identification Using Rapid Evaporative Ionization Mass Spectrometry

In this study, we integrate rapid evaporative ionization mass spectrometry (REIMS) with the Harmonic scalpel, an advanced laparoscopic surgical instrument that utilizes ultrasound energy to dissect and coagulate tissues. It provides unparalleled manipulation capability to surgeons and has superseded traditional electrosurgical tools particularly in abdominal surgery, but is yet to be validated with REIMS. The REIMS platform coupled with the Harmonic device was shown to produce tissue-specific lipid profiles through the analysis of porcine tissues in both negative and positive ionization modes. Comparison with other methods of electrosurgical dissection, such as monopolar electrosurgery and CO₂ laser, showed spectral differences in the profile dependent on the energy device used. The Harmonic device demonstrated major spectral differences in the phospholipid region of m/z 600–1000 compared with the monopolar electrosurgical and CO₂ laser-generated spectra. Within the Harmonic REIMS spectra, high intensities of diglycerides and triglycerides were observed. In contrast, monopolar electrosurgical and laser spectra demonstrated high abundances of glycerophospholipids. The Harmonic scalpel was able to differentiate between the liver, muscle, colon, and small intestine, demonstrating 100% diagnostic accuracy. The validation of the Harmonic device–mass spectrometry combination will allow the platform to be used safely and robustly for real-time in vivo surgical tissue identification in a variety of clinical applications.

Mass spectrometry transanal minimally invasive surgery (MS-TAMIS) to promote organ preservation in rectal cancer

BACKGROUND

Transanal minimally invasive surgery (TAMIS) is deployed for organ preservation in early rectal cancer and significant rectal polyps. Rapid evaporative ionisation mass spectrometry (REIMS) provides biochemical tissue analysis, which could be applied intraoperatively to give real-time tissue feedback to the surgeon and decrease the risk of an involved margin. However, the accuracy and feasibility of this approach have not been established.

METHODS

In this prospective observational study, patients undergoing resection of rectal adenomas or carcinomas were recruited. An electrosurgical handpiece analysed tissues ex vivo using diathermy, with the aerosol aspirated into a Xevo G2-S ToF mass spectrometer. The relative abundance of lipids underwent predictive statistical modelling and leave-one-patient-out cross-validation. The outcomes of interest were the ability of REIMS to differentiate normal, adenomatous and cancerous tissue, or any disease subtype from normal. REIMS was coupled with TAMIS for in vivo sampling, assessing the accuracy of tissue recognition and distinguishing bowel wall layers.

RESULTS

Forty-seven patients were included, yielding 266 spectra (121 normal, 109 tumour and 36 adenoma). REIMS differentiates normal, adenomatous and cancerous rectal tissues with 86.8% accuracy, and normal and adenomatous tissue with 92.4% accuracy and 91.4% accuracy when differentiating disease from normal. We have performed the first five in-man mass spectrometry augmented TAMIS (MS-TAMIS). In real time, MS-TAMIS can differentiate rectal mucosa and submucosa based on their relative abundance of triglycerides and glycerophospholipids. The ex vivo accuracy distinguishing diseased and normal tissues is maintained in vivo at 90%, with negative predictive value of 95%. The system identified a deep and lateral involved tumour margin during TAMIS.

CONCLUSIONS

REIMS distinguishes rectal tissue types based on underlying lipid biology, and this can be translated in vivo by coupling it to TAMIS. There is a role for this technology in improving the efficacy of resection of early rectal cancers.

Abstract 4536: Rapid evaporative ionization mass spectrometry (REIMS) analysis of the mucosal lipidome has a high diagnostic accuracy for adenomas and early colorectal cancer

Introduction

The aim of this study was to determine the diagnostic accuracy of REIMS for dysplasia in human adenomas and early colorectal cancer and to determine changes in mucosal lipid chemistry during cancer initiation. Moreover, we attempted to develop a proof of concept first in man study of a novel REIMS-based endoscope for in-vivo chemical phenotyping of adenomas based on the real time analysis of phosphatidic acid (PA) and phosphatidylethanolamine (PE) metabolism.

Experimental procedure

A prospective, observational cross-sectional cohort study was performed in patients undergoing elective resection for colorectal cancer or colonoscopy at Imperial College London NHS Trust. Two tissue types were obtained - early colorectal cancer (defined as T1 or T2 according to TNMv6 criteria) and adenomatous polyps. Patients with familial adenomatous polyposis, inflammatory bowel disease or hereditary non-polyposis colon cancer were excluded. Specimens were analyzed ex-vivo using a modified electro-surgical hand piece with the aerosol aspirated into a Xevo G2-S QTof mass spectrometer (Waters Corporation). Multivariate analyses were used to create models which underwent cross-validation using SIMCA (V14, Umetrics, Sweden). Characteristic lipid species were identified using univariate statistics in R Studio (V1.0.44) and Metlin. An endoscopic set up was created using a standard endoscope for proof of concept.

Summary of data

19 patients (12:7 F:M) were included with a median age of 74 (range 50-92). Six patients had T1/2 adenocarcinoma and 13 had adenomatous polyps. REIMS was able to accurately distinguish the presence of low grade dysplasia (LGD) vs high grade dysplasia (HGD) in adenomatous polyps (sensitivity 95.0%, specificity 100%). Phosphatidic acids (PA) 38:2 and 38:1 were more abundant in high vs low grade dysplasia (p=0.003). REIMS was also able to identify adenomatous polyps from early cancer (sensitivity 100%, specificity 96.3%). Phosphatidylethanolamine (PE) 36:1, phosphatidic acid (PA) 38:1, glucosylceramide (Glc-Cer) 30:1 and ceramide phosphoethanolamines (PE-Cer) d16:1(4E)/20:0 and d14:1(4E)/22:0 were associated with early cancer formation rather than adenomas (p<0.001, p<0.001, p=0.03, p=0.04 respectively). Endoscopic REIMS was successfully deployed in-vivo in six patients undergoing polypectomy. Spectra with good signal to noise ratio were acquired and the technology was able to correctly stratify adenomas.

Conclusion

Dysplastic adenomas exhibit mucosal lipid chemistry that is discrete from early colorectal cancer. PA, PE and Glc-Cer have potential use as diagnostic biomarkers. First in man studies of the endoscopic application of REIMS suggest it could serve as a real-time tool for early cancer detection based on in vivo analysis of the mucosal lipidome.

Citation Format: Petra Paizs, Eftychios Manoli, Sam E. Mason, James L. Alexander, Zsolt Bodai, Emma White, Afeez Adebesin, Jonathan Hoare, Robert Goldin, Ara W. Darzi, James M. Kinross, Zoltan Takats. Rapid evaporative ionization mass spectrometry (REIMS) analysis of the mucosal lipidome has a high diagnostic accuracy for adenomas and early colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4536.