MSACL 2019 EU Abstract

Self-Classified Topic Area(s): Tissue Imaging

Strategy for the Prediction of Neoadjuvant Therapy Response in Breast Cancer by MALDI-MSI

Caro Thomassen,1,2ǂ Michele Genangeli,1,3ǂ Renée Granzier,2,4,5 Jo Capell,1 Fanny Boyaval,1 Loes Kooreman,4,6 Briete Goorts,2,4,5 Ron M.A. Heeren,1 Marjolein Smidt,2,4 Tiffany Porta Siegel1,*
1 The Maastricht Multimodal Molecular Imaging Institute (M4I), Maastricht University, R Maastricht, The Netherlands 2 Department of Surgical Oncology, Maastricht University Medical Centre, Maastricht, The Netherlands 3 School of Pharmacy, University of Camerino, Camerino (MC), Italy 4 GROW - School for Oncology and Developmental Biology, Maastricht University Medical Centre, Maastricht, The Netherlands 5 Department of Radiology, Maastricht University Medical Centre, Maastricht, The Netherlands 6 Department of Pathology, Maastricht University Medical Centre, Maastricht, The Netherlands

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Tiffany Porta (Presenter)
M4I institute, Maastricht University

Relevant Financial Disclosures (within past 24 months)

Committee/Board/Advisory Board MSACL Tissue imaging track Sci Committee; MSIS board

Discussing Products? NO, presenter will NOT present educational content related to products/services of the ineligible company(ies) listed above.

Conflict mitigation NOT REQUIRED.

Abstract

Introduction
Breast cancer is the most prevalent cause of cancer in women worldwide. Despite recent advances in the chemotherapeutic area, the response to therapy varies considerably from on patient to another. Responses can range from pathologic complete response (pCR) to non-response, with the progression of the tumor at worst. Predicting pCR non-invasively in breast cancer after neoadjuvant systemic therapy (NST) remains a challenge, as it can be difficult to visualize the tumor. Therefore, surgery remains the only treatment option; even when MRI scans show a pCR. Here, we investigate and demonstrate the ability of MALDI mass spectrometry imaging to predict the response to NST at an early stage of the patient’s management, from tissue biopsies taken before treatment.

Methods
Our study includes 27 female patients with invasive ductal carcinomas (tumor size ≥ 2 cm and/or lymph metastasis); who received 24 weeks of chemotherapy and/or immune therapy before surgery (i.e. NST). Biopsies were obtained during ultrasound before NST; and immediately fixed in formalin and embedded in paraffin. Tissue samples were prepared for MALDI-MSI analysis as follow: 1) sectioning into 5 um tissue sections; 2) deparaffinization and rehydration; 3) antigen retrieval and on-tissue tryptic digestion; 4) matrix application. MALDI-MSI experiments were performed on a Rapiflex Tissuetyper (Bruker, Bremen, Germany) operated in reflectron and positive ion mode in the mass ranges m/z 600-3000. Images were acquired at a spatial resolution of 50 x 50 µm2.

Results
One of the challenge with MALDI-MSI is to monitor complex sample preparation that allows analyzing FFPE tissue; as the analysis of clinical cohorts lies in the analysis of multiple samples over several days. Therefore, we developed a strategy which makes use of pork fat FFPE tissue assess and monitor on-tissue trypsin digestion efficiency, day-to-day variability (e.g. humidity, temperature) and experimental variability. PCA analysis of the pork fat data enabled to identify outliers and days where deviation in sample preparation hampered the analysis of the clinical samples. With this strategy, we were able to remove in a reliable way the BC samples with poor digestion from the analysis. After exclusion of outliers, a statistical model based on Partial Least Squares regression (PLS-DA) was built and allowed to classify samples pCR with a correct classification rate better than 95%.

Conclusion
We developed adequate quality controls to monitor the complex sample preparation process to analyze clinical cohorts by MALDI-MSI. With this strategy, we were able to reveal molecular (peptide) patterns able to classify breast cancer patient accordingly to their pathologic response to treatment.