Title: Elucidating the immune active state of HR+HER2- MammaPrint High 2 early breast cancer

Publication: ASCO 2024, Abstract #506

Authors: Erin Frances Cobain, Lajos Pusztai, Cathy Lynne Graham, Pat W. Whitworth, Peter D. Beitsch, Cynthia R. C. Osborne, Rakhshanda Layeequr Rahman, Nathalie M. Johnson, Adam Brufsky, Reshma L. Mahtani, VK Gadi11, Kent Hoskins, Hannah M. Linden, Rita A. Mukhtar, Laura Esserman, Josien Haan, Katie Quinn, Andrea Menicucci, William Audeh, Joyce O’Shaughnessy, FLEX Investigators Group

Introduction: The 70-gene signature, MammaPrint (MP), classifies patients (pts) with early-stage breast cancer (EBC) as having an UltraLow, Low, High 1 (H1), or High 2 (H2) risk of distant recurrence. The I-SPY 2 trial showed that pts with MP H2, HR+HER2- tumors have significantly higher response rates to neoadjuvant chemotherapy plus immunotherapy relative to pts with MP H1 tumors. Expression-based immune deconvolution provides more detailed information about immune cell function beyond conventional methods enumerating tumor infiltrating lymphocytes. To elucidate the underlying biology that mediates immune therapy response, we performed in silico analysis of full transcriptome data to characterize immune cell frequencies and antigen presentation in HR+HER2-, MP High Risk EBC from pts enrolled in FLEX.