Abstract PO3-01-02: Real world outcomes of neoadjuvant therapy with Trastuzumab and Pertuzumab associated with carboplatin and docetaxel (TCHP) in HER2+ early breast cancer patients unfit for anthracyclines: a retrospective cohort comparative study

Abstract Backgound Neoadjuvant chemotherapy (CT) with anti-HER2 blockade using trastuzumab (H) and pertuzumab (P) is a standard of care for patients (pts) with HER2-positive early-stage Breast Cancer (eBC). Historically, taxanes (T) and anthracyclines (A) have been the mainstays of (neo)adjuvant CT in this setting, but the added benefit of A in the era of anti-HER2 therapy has been questioned. This study aimed to assess the effectiveness, cardiac safety, and cost-effectiveness of an anthracycline-free regimen (TCHP) in a real-world population of pts deemed unfit for A, compared to pts treated with the standard regimen of doxorubicin and cyclophosphamide plus dual-blockade associated with docetaxel (AC-DHP) at a single Portuguese Comprehensive Cancer Center. Methods This retrospective cohort study included a consecutive series of female eBC HER2+ pts who initiated primary treatment with TCHP between July 2018 and August 2022. The primary endpoint was pathological complete response (pCR), and secondary endpoints were cardiac safety and disease-free survival (DFS). The outcomes were compared with a historical database of eBC HER2+ pts who started primary treatment with AC-DHP between August 2015 and May 2021. Clinical data was collected from medical and administrative records. Descriptive statistics were used to describe categorical and continuous variables, and the Kaplan-Meier method was used for DFS analysis. Costs analysis employed the micro-costing technique, considering individual medical direct costs from diagnosis until surgery. Multivariate logistic regression models were used for effectiveness analysis and the gamma general model for costs analysis. The incremental cost-effectiveness ratio (ICER) was calculated using the pCR rate as a measure of effectiveness. Results A total of 233 and 23 pts were included in the TCHP and AC-DHP groups respectively. Reasons for choosing the anthracycline-free regimen in the TCHP group were primarily age-related frailty (52%), medical comorbidities (26%), and previous exposure to anthracyclines (22%). The TCHP pts were older (median age 71 years, range 45-77 vs. 47 years 24-70) and had lower baseline Left Ventricular Ejection Fractions (LVEF) (median 65% 51-80 vs. 60% 56-73), with a higher proportion of hormone receptor (HR) negative pts (78.3% vs. 33.0%). Clinical stages were balanced between groups, but the TCHP group had a higher nodal involvement (N+) (73.9% vs. 61.8%). The pCR rates were higher in the TCHP group (65.2% vs. 46.1%, HR 0.98 95% CI 0.36 - 2.70). Subgroup analysis by HR status showed comparable pCR rates: 77.1% vs. 74.1% in HR- pts and 40% vs. 39.7% in HR+ pts. Cardiac safety analysis indicated a median decrease in LVEF of 9% in both the TCHP and AC-DHP groups, with 43.5% of TCHP pts experiencing a decline of 10% or more, and 13.0% dropping below 50%. In comparison, these figures were 44.2% and 3.9%, respectively, in the AC-DHP group. At the end of the follow-up, only one patient in the TCHP group with a LVEF 50% persisted with mild symptoms of chronic heart failure. The median follow-up time for DFS events, starting from surgery, was 31.1 months in the TCHP group and 45.7 months in the AC-DHP group, with 1-year DFS rates of 91.3% and 100%, respectively. The ICER analysis indicated that TCHP was cost-effective, as the incremental cost for achieving an additional pCR in similar subgroups can be outweighed by later cost savings, mainly due to further adjuvant treatment with trastuzumab instead of TDM-1. Conclusions In a real-world population of HER2+ eBC patients unfit for anthracyclines, the TCHP regimen demonstrated a higher overall pCR rate compared to a historical control treated with the AC-DHP regimen, along with an acceptable cardiac safety profile. These results support the broader use of the TCHP regimen in HER2+ eBC pts, as recommended by current NCCN guidelines. However, larger studies involving similar populations are needed to provide higher levels of evidence. Citation Format: Ricardo Pinto, Rita Calisto, Patrícia Redondo, Ana Silva, Pedro Castro, Rute Fernandes, Raquel Teixeira, Diana Mata, Ana Ferreira, Maria Bento, Cláudia Vieira. Real world outcomes of neoadjuvant therapy with Trastuzumab and Pertuzumab associated with carboplatin and docetaxel (TCHP) in HER2+ early breast cancer patients unfit for anthracyclines: a retrospective cohort comparative study abstract. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-01-02.