Background: The addition of neoadjuvant platinums to standard chemotherapy regimens for triple negative breast cancer (TNBC) improves rates of pathologic complete response (pCR). Our prior trial combining carboplatin (CAR) with liposomal doxorubicin (DOX) for metastatic TNBC showed good response rates with minimal side effects and allows for higher platinum dosing. We hypothesized that the doublet of DOX+CAR is effective and tolerable in the neoadjuvant setting for TNBC and tumor genomics may identify biomarkers of complete response and actionable targets. Methods: A phase II single arm trial was conducted for patients (pts) diagnosed with stage II-III TNBC. Patients received 4 cycles of neoadjuvant carboplatin (AUC 5) and liposomal doxorubicin (30mg/m2) administered every 28 days, then underwent definitive breast surgery followed by 12 weeks of adjuvant paclitaxel 80 mg/m2 administered weekly. Primary and secondary clinical endpoints were rate of pCR and two year recurrence free survival (RFS) and overall survival (OS), respectively. Cardiac safety of the combination was assessed. Fresh residual tumor samples were obtained at time of surgery for generation of patient derived xenografts (PDX). Whole genome sequencing (WGS) and RNA sequencing will be performed to evaluate specific patterns of small-variant mutations and patterns of structural variants to identify which patients are likely to have pCR. Results: From 2/2015 to 6/2021, 62 pts were enrolled, 8 pts withdrew consent either prior to treatment or completion of neoadjuvant therapy and/or surgery. Median age of the cohort was 55.4 years. There was high participation by under-represented groups: 17.0% African American, 20.8% Asian, 13.2% Hispanic. Most histologies were invasive ductal carcinoma, but included apocrine, pleomorphic lobular, and metaplastic subtypes. 53 pts completed all 4 cycles of neoadjuvant DOX+CAR, followed by definitive surgery; 1 pt progressed after 1 cycle and proceeded to surgery thereafter. 30.2% (16) pts achieved pCR, and residual cancer burden (RCB) will be reported in patients with residual disease. Of the 53 pts who completed 4 cycles of treatment, 5 pts progressed (recurrence or death) within two years from time of surgery (4 distant and 1 local recurrence), yielding the 2-year recurrence-free-survival rate of 90.3% (95%CI 81.0%, 99.6%). The most common toxicities during DOX+CAR were grade 1 fatigue in 50 pts (92.6%), grade 1 anemia in 44 pts (81.5%), and grade 3/4 neutropenia in 16 pts (29.6%); these pts received GCSF support with subsequent cycles; febrile neutropenia occurred in 1 pt (1.9%) in this group. Only 10 pts (18.5%) had grade 1 alopecia, 5 pts (9.3%) had grade 2 alopecia, 2 pts (3.7%) had grade 3 thrombocytopenia. There were no delays in treatment due to cardiotoxicity or complications from surgical healing. Of the 37 pts who had residual disease, PDX was attempted in 21 pts, and 16 (76%) PDX were established, including those for 4 patients experiencing recurrence. WGS and RNA sequencing data from pre-treatment and residual disease samples will be analyzed and reported.Conclusion: 4 cycles of neoadjuvant DOX+CAR achieved rate of pCR similar to standard regimens and has good tolerability. Post chemotherapy PDX is feasible and may help identify targeted approaches for patients with resistant disease. These results warrant further evaluation of this combination for early stage TNBC.

Citation Format: Nancy Chan, Shou-en Lu, Yue Wang, Gregory M Riedlinger, Coral Omene, Mridula George, Jyoti Malhotra, Maria Kowzun, Firas G Eladoumikdachi, Lindsay B Potdevin, Shicha Kumar, Kant Matsuda, Shruti Desai, Nayana Patel, Deborah L Toppmeyer, Shridar Ganesan, Kim Hirshfield. Neoadjuvant liposomal doxorubicin and carboplatin is effective and tolerable for the treatment of early stage triple negative breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P2-12-15.