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e11542 Background: BRCA1 mutation is associated with the TNBC phenotype. Loss of BRCA1, due to genetic mutation or post-genomic inactivation, should confer susceptibility to DNA-damaging agents, such as anthracyclines, but resistance to mitotic-spindle poisons such as taxanes. However, optimal adjuvant systemic therapy for TNBC is difficult to define because of a lack of prospective data in TNBC restricted populations. As our neo-adjuvant regimen changed in 2008 (A followed by D before 2008 then D followed by A from 2008); we were able to compare retrospectively A and D efficacy in matched cohorts of TNBC treated in neo-adjuvant setting. Methods: Group 1 includes 24 patients with TNBC treated between 2005 and 2008 with A followed by D (3x 5FU 500 mg/m², epirubicine 100 mg/m², cyclophosphamide 500 mg/m² followed by 3x docetaxel 100 mg/m²). Group 2 includes 24 patients with TNBC treated in NAS between 2008 and 2011 with D followed by A. Characteristics of group 1 and 2 (median age at diagnosis, tumor grade, Ki67, TNM) were similar. All patients had a core-biopsy before chemotherapy. Chemotherapy response was evaluated by CT scan before 1st cycle, between 3rd and 4th cycle then after the 6th cycle. Surgery was performed 4 weeks after the 6th cycle. Results: In group 1, objective response rate after 3 cycles was 58% (14/24) (RECIST criteria). There was no progression. Complete pathological response rate (no residual invasive and in-situ tumor in breast, no tumor in axillary nodes) was 25%. In group 2, objective response rate after 3 cycles was 25% (6/24). Progression rate was 13% (3/24). Complete pathological response rate was 29%. The objective response rate after the first three cycles was significantly different between group 1 and group 2 (two-sided p-value = 0,039, Fisher exact test). Conclusions: Our retrospective analysis showed that docetaxel was significantly less efficient than anthracycline-based chemotherapy in chemo-naïve TNBC patients. These data should be taken in consideration for clinical practice and further phase III trials design in TNBC.

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