25P - Feasibility of digital spatial profiling as a diagnostic: Comparison to immunohistochemistry (IHC)

Background

Digital Spatial Profiling (DSP) is an alternative method to IHC for quantitative assessment of multiple proteins on a single tissue section; with spatial context of all markers in relation to each other. DSP offers the potential for patient treatment decisions not relying on manual interpretation, with the added value of preserving tissue.

Methods

This proof-of-concept study investigated DSP as an alternative method to the assessment of PD-L1 (22C3), HER2 (4B5) and cMET (SP44) IHC. The dynamic range of each biomarker was assessed using the GeoMx© DSP protein assay and quantified on the nCounter© platform. 34 commercial Non Small Cell Lung Cancer cases were assessed using IHC and DSP. For DSP, up to 20 650μm² regions of interest (ROIs) were placed across each tissue to sample the whole tumor; same slide pan-cytokeratin immunofluorescent staining was used as a guide to identify cells of epithelial origin. Median digital counts (Log₂ normalised to endogenous protein GAPDH) were compared to the % of tumor cells stained with each IHC assay as assessed by a board-certified pathologist.

Results

Median DSP counts demonstrated a non-linear, positive correlation to the % of tumor cells stained with PD-L1, HER2 and cMET (R² = 0.452, 0.434,0.402). The table shows average counts in IHC defined groups. Coefficient of variation was used to assess intra case heterogeneity across ROIs and ranged from 0.32-2.1 for PDL1, 0.2-1.9 for HER2 and 0.17 to 1.1 for cMET. Table: 25P

Conclusions

Biomarker heterogeneity and thresholds of protein expression are important for determining patient response. DSP potentially overcomes challenges associated with determining tumor heterogeneity. This study successfully used the GeoMx© technology to demonstrate spatial heterogeneity and correlation against IHC; showing spatial variance may have value beyond the single IHC score in predicting patient response. Further investigation and validation of DSP technologies in a clinical setting is warranted.

Editorial acknowledgement

Clinical trial identification

Legal entity responsible for the study

AstraZeneca PLC.

Funding

AstraZeneca.

Disclosure

H. Hibbs, J. Gerrard, S. Hoffmann, M. Scott, D. Duncan: Financial Interests, Personal, Full or part-time Employment: AstraZeneca; Financial Interests, Personal, Stocks/Shares: AstraZeneca. M. Vandenberghe: Financial Interests, Personal, Stocks/Shares: AstraZeneca; Financial Interests, Personal, Full or part-time Employment: AstraZeneca.