Synergizing microdissection with ddPCR to advance precision oncology.

Abstract

e15083 Background: Improving patient treatment outcomes based on the application of advanced molecular profiling methodologies applied to pathological specimens is the purview of precision oncology. Optimal utilization of tumor tissue from diagnostic biopsies remains an unmet medical need. This is especially relevant today since precision oncology is a rapidly evolving field where timely tumor genotyping is essential for the indication of many advanced and targeted therapies. National Comprehensive Cancer Network (NCCN) guidelines now mandate molecular testing for clinically actionable targets in certain malignancies. Patients diagnosed with advanced non-small cell lung cancer (NSCLC) are commonly of an older age and have significant co-morbidities. Clinical dilemmas regarding the ability to obtain adequate amounts of tissue for tumor genotyping frequently occur. In these cases, the tumor tissue may have been obtained by an image-guided biopsy, and the diagnosis of NSCLC proper determined via cytology. Adequate tissue for tumor genotyping and/or a more advanced mutational analysis to identify oncogenic drivers may not be available, and the opportunity to explore more optimal therapy options (eg, TKI in lieu of chemotherapy) is lost. Methods: Following a formal pathology review formalin fixed paraffin embedded (FFPE) specimens were examined using advanced immuno-based laser capture microdissection (LCM). In preparation for droplet digital PCR (ddPCR), nucleic acids were extracted from samples and run with a series of positive and negative controls. Results: Utilizing lung cancer as an example, an improved genotyping approach for NSCLC solid tumors was developed and tested. The strategy involves optimization of the microdissection process and analysis of a large number of identical target cells from FFPE specimens sharing similar characteristics, in other words, single-cell subtype analysis. Immunostaining status, cell phenotype, and spatial location within a histological section are examples of shared characteristics that can guide cell procurement. Conclusions: With this approach, tumor molecular analysis is enhanced through the synergy between microdissection and ddPCR. Here we demonstrate a methodology that illustrates genotyping of a solid tumor from a small tissue biopsy sample in a time and cost-efficient manner, using immunohistochemistry-directed LCM along with the detection and absolute quantitation of mutations by ddPCR.