Association of molecular subtype, proliferation, and immune genes with efficacy of carboplatin versus gemcitabine addition to taxane-based, anthracycline-free neoadjuvant chemotherapy in early triple-negative breast cancer (TNBC): Results of the randomized WSG ADAPT-TN trial

573 Background: In the ADAPT-TN neoadjuvant trial, 12-week nab-paclitaxel (nab- pac)+carboplatin (carbo) was highly effective and superior to nab-pac+gemcitabine (gem). However, within TNBC, reliable predictive markers for carbo use have yet to be identified. Methods: Patients with early TNBC (centrally confirmed) were treated by nab-pac 125 mg/m2 with either carbo AUC2 or gem 1000 mg/m2 d 1,8 q21 given for 4 cycles. Genomic data (80 genes) and Prosigna (PAM-50) scores were available in 306 pre-therapeutic samples of 331 treated patients. Fisher’s exact test was performed for pCR differences; associations of continuous measurements or scores with pCR were analyzed by the Mann-Whitney statistic. Results: pCR was 44.5% to 28.4% (p=.004) in favor of nab-pac - carbo. Specifically within the carbo- containing arm, immunological (CD8, PD1, PFDL1) genes and proliferation markers (proliferation score and ROR scores, MKI67, CDC20, NUF2, KIF2C, CENPF, EMP3, TYMS) were positively associated with pCR (p