Molecular subtypes of triple negative breast cancer (TNBC) tumor samples obtained before and after neoadjuvant systemic therapy (NST) and relationship between immunomodulatory …

12069Background: Lehmann et al have identified 4 molecular subtypes of TNBC [basal-like (BL) 1, BL2, mesenchymal (M), and luminal androgen receptor (LAR)] and an IM gene expression signature. Our group previously showed that response of TNBC to NST differs by molecular subtype, but whether NST affects TNBC subtype has not been studied. We hypothesized that certain TNBC subtypes change after NST. We also tested whether IM signature correlates with the intensity of TILs. Methods: From the World TNBC Consortium dataset, which contains TNBC samples from 4 institutions from 4 countries, we examined 68 formalin-fixed, paraffin-embedded tumor samples from patients treated with NST: 27 pairs of matched pre-NST and post-NST samples and 14 pre-NST samples. TNBC classification was performed with the Insight TNBCtype assay. We compared the molecular subtypes of TNBC samples obtained …