Menelaos Tzafetas (Presenter)
Imperial College London
Bio: Dr Menelaos Tzafetas is a Clinical Research Fellow in Gynecology at Imperial College London, with a particular interest in the use of mass spectrometry technologies for improving clinical practice and patient experience satisfaction in cervical cancer and pre-cancer treatment services.
Authorship: Menelaos Tzafetas(1), Anita Mitra(1), Ilkka Kalliala(1), Zsolt Bodai (2), Francesca Rosini (3), David Phelps (1), Adele Savage (2), Rashpal Flora (3), Sadaf Ghaem-Maghami (1), Zoltan Takats (2), Maria Kyrgiou (1).
1. Department of Surgery and Cancer Imperial College London 2. Department of Computational and Systems Biology Imperial College London 3. Department of Histopathology Imperial College Healthcare NHS Trust
Cervical cancer and its precancerous form cervical intraepithelial neoplasia (CIN) commonly affect women of reproductive age. Fertility-preserving procedures fail at rates of 33% due to incomplete excision. Rapid Evaporative Ionization Mass Spectrometry(REIMS) analyzes electrosurgery-generated aerosols, using time-of-flight mass spectrometry to provide real time tissue identification without the need for sample preparation, raising the potential for intraoperative use. We conducted a pilot study showing that REIMS can differentiate between cancerous and healthy cervical tissue thus presenting an innovative technique that could improve fertility-sparing operations. Currently we are investigating the application of REIMS for identification of CIN abnormalities and its direct use in the colposcopy clinic.
Cervical cancer and its precancerous form cervical intraepithelial neoplasia (CIN) are common diseases in women of reproductive age and are caused by the Human Papilloma virus (HPV), of which there are 15 oncogenic subtypes. Cervical cancer is the fourth most commonly diagnosed cancer type amongst women worldwide. Fertility preserving treatments are available for these patients, but if the excisional margins are not clear from cancer, as is the case in 33% of current procedures, these women have to undergo a hysterectomy, therefore losing their childbearing potential. We conducted a study showing that Rapid Evaporative Ionization Mass Spectrometry (REIMS) can be used for real time identification of cervical pathology with the potential to improve surgical outcomes of such fertility-sparing operations.
Fresh frozen cervical biopsies were cut using a Covidien diathermy hand-piece. The surgical aerosol produced was transferred into a Waters Xevo G2-S mass-spectrometer equipped with a REIMS ion source. The scan range was 50-1200 Da, with one second scan time, in negative ion mode and 2-propanol as the matrix solvent at 0.1 ml/min. Following REIMS, the samples were stained for histopathological validation.
These diagnoses were used in multivariate statistical analysis of spectral data, including principal component (PCA) and linear discriminant analysis (LDA). Internal lock mass (699.947m/z) correction was employed, with m/z bining of 0.01. Correct classification rate was checked using leave one patient out cross-validation. HPV genotyping information for these samples will be combined with the current analysis.
Cervical samples from 66 patients met the inclusion criteria; 26 cervical cancer patients and 40 healthy controls. They were analysed in the cut diathermy mode to give 158 spectra; 73 spectra from cancerous tissue and 85 from normal tissue. After the data analysis, spectral differences were observed between normal and cancerous cervical tissues in the 500-1000m/z range. From the raw data retrieved, exact m/z values of predominant spectral peaks were identified and were used for compound identification via database search (Metlin). The peak at 744.56 m/z was found to be significantly raised in cervical cancer tissues, which may represent PE(36:1). Further metabolite identification and MSMS fragmentation is being performed. The data was imported to the Offline Model Builder (OMB) software and combined PCA/LDA model was used for tissue classification. To test the classification rate of the built model, leave one patient out cross validation was applied. Leave one patient out cross-validation resulted in correct detection rate of 96% overall. Furthermore, we are processing 115 samples from women with CIN and analysing these results in combination with HPV genotype, to investigate the potential correct identification between low grade and high grade precancerous abnormalities with the use of REIMS.
Conclusions & Discussion
Frozen section is the current method for intraoperative assessment of margin status at the time of trachelectomy, and the concordance between intraoperative frozen section and final histology has been quoted as 84%, significantly lower than the preliminary results of REIMS. In addition to providing real-time information, thus reducing anaesthetic time, REIMS has the potential to improve the accuracy of intraoperative margin detection. This could potentially increase success rates of trachelectomy, leading to a truly advanced fertility sparing technique in modern surgery. This principle is also under investigation for use in CIN, with good potential of correct identification between normal, low grade and high grade cervical abnormalities which would lead to the immediate application of this technique into the colposcopy clinic.
References & Acknowledgements:
IP Royalty: no
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