A randomized phase II trial investigating the addition of carboplatin to neoadjuvant therapy for triple-negative and HER2-positive early breast cancer (GeparSixto).

Abstract

1004 Background: Use of carboplatin in neoadjuvant chemotherapy (NACT) has never been prospectively examined in breast cancer. Cohort studies suggest a high sensitivity to DNA-damaging agents (e.g., carboplatin in triple negative breast cancer [TNBC]), which have a high prevalence of BRCA mutations. Two trials examining carboplatin in HER2+ metastatic disease have shown conflicting results, but one was biased by different dosage of docetaxel in treatment arms. GeparSixto investigates the impact of carboplatin in addition to an identical, optimized cytotoxic-targeted regimen on pathological complete response (pCR) in these two breast cancer subtypes. Methods: In GeparSixto trial (NCT01426880) patients were treated for 18 weeks with paclitaxel 80mg/m² q1w and non-pegylated-liposomal doxorubicin (NPLD) 20mg/m² q1w. HER2+ patients received concurrently trastuzumab 6(8) mg/kg q3w and lapatinib 750mg daily. TNBC patients received concurrently Bevacizumab 15mg/kg i.v. q2w. All patients were randomized 1:1 to receive concurrently carboplatin AUC 1.5-2 q1w vs not, stratified by subtype. Primary objective is pCR rates (ypT0 ypN0), secondary objectives are pCR rate in predefined subgroups or by other definitions, clinical response rate, compliance and tolerability of carboplatin. Carboplatin dose was reduced from AUC 2.0 to 1.5 by an amendment after 330 patients due to carboplatin-related toxicity at pre-planned safety analyses. Results: 595 patients were recruited (8/2011 - 12/2012) in 51 German centers, 299 did not receive carboplatin. Median age was 47/48 years (no carb/carb), 36.8/36.5% were postmenopausal; 14.0/13.3% had T3, 5.0/3.7% T4, 41.8/37.6% N+, 93.0/92.9% ductal invasive, 64.5/65.3% G3 tumors; 46.2/46.3% had HER2+, 53.8/53.7% TNBC. 225 patients had a SAE (149 no carb/177 carb) and 3 died (postoperative pneumonia; reduced general condition; acute myocardial infarct), all in no carb arms. Final analysis on primary endpoint will be presented. Conclusions: This is first study, evaluating efficacy and safety of the addition of carboplatin to anthracycline-taxane containing NACT in patients with primary HER2+ and TNBC. Clinical trial information: NCT 01426880.