['To provide optimal treatment of heterogeneous triple negative breast cancer (TNBC), we need biomarkers that can predict the chemotherapy response.', 'We retrospectively investigated BRCAness in 73 patients with breast cancer who had been treated with taxane- and/or anthracycline-based neoadjuvant chemotherapy (NAC). Using multiplex, ligation-dependent probe amplification on formalin-fixed core needle biopsy (CNB) specimens before NAC and surgical specimens after NAC. BRCAness status was assessed with the assessor unaware of the clinical information.', 'We obtained 45 CNB and 60 surgical specimens from the 73\xa0patients. Of the 45 CNB specimens, 17 had BRCAness (38.6% of all subtypes). Of the 23 TNBC CNB specimens, 14\xa0had BRCAness (61% of TNBC cases). The clinical response rates were significantly lower for BRCAness than for non-BRCAness tumors, both for all tumors (58.8% vs. 89.3%, P\xa0= .03) and for TNBC (50% vs. 100%, P\xa0= .02). All tumors that progressed with taxane therapy had BRCAness. Of the patients with TNBC, those with non-BRCAness cancer had pathologic complete responses significantly more often than did those with BRCAness tumors (77.8%\xa0vs. 14.3%, P\xa0= .007). After NAC, the clinical response rates were significant lower for BRCAness than for non-BRCAness tumors in all subtypes (P\xa0= .002) and in TNBC cases (P\xa0= .008). After a median follow-up of 26.4 months, 6 patients-all with BRCAness-had developed recurrence. Patients with BRCAness had shorter progression-free survival than did those with non- BRCAness (P\xa0=\xa0.049).'] Does bRCAness predict resistance to taxane-containing regimens in triple negative breast cancer during neoadjuvant chemotherapy?