A retrospective, single-center study comparing two neoadjuvant protocols for patients with HER2-positive breast cancer.

e12623 Background: Neoadjuvant treatment is common in Stage 2+3 HER2 positive tumors. Cytotoxic and anti-HER2 drug combinations are used. Pathological complete response (pCR) correlates with improved survival and decreased risk of relapse. Trastuzumab may cause temporarily congestive heart failure (CHF) while anthracyclines may cause irreversible CHF. Current guidelines advise non-anthracycline based regimens. Here, we compare the efficacy and toxicity of these two regimens. Methods: Retrospective data were collected on 179 patients with clinical stage II-III, who received neoadjuvant treatment with either 6 cycles of DCHP (Docetaxel, Carboplatin AUC6 53.2% received AUC5, Trastuzumab, Pertuzumab) or ACTHP (doxorubicin, cyclophosphamide followed by weekly Paclitaxel combined with HP). According to pCR response post surgery, adjuvant HP or TDM-1 were given to go complete one year of treatment. Efficacy Indices of pCR were evaluated in both cohorts and according to HER2 IHC staining (3+ or 2+ FISH positive), hormone receptor (HR) and nodal status. Toxicity indices were reductions in left ventricular ejection fraction (LVEF), dose reductions, hospitalizations and febrile neutropenia. Results: Between 9.2017 and 6.2022, 106 patients received ACTHP and 73 received DCHP. Median age at diagnosis, HR status, HER2 IHC (2+FISHpos or 3+) and nodal status were balanced. PCR occurred in 63.1% of all patients, numerically higher in the ACTHP group at 67.0% vs. 57.5% in the DCPH group (p=0.129). Symptomatic LVEF decrease (>10% or LVEF≤50%) was observed in 6.6% of the ACTHP group vs. 0% in the DCHP group (p<0.001). Hospitalization rates were similar (14%). Dose reductions occurred more often in the DCHP regimen vs ACTHP (54.8% vs 24.5% respectively) (p<0.00001) mostly due to asthenia and diarrhea. Febrile neutropenia was slightly higher in the ACTHP group but not statistically significant. Conclusions: In this study, pCR rates were numerically better in the ACTHP regimen vs. DCHP, though not statistically significant. Dose reductions were more common in the DCHP but had less cardiotoxicity. pCR rates were relatively low in both regimens where Her-2 +2, FISH pos. This study shows that the DCHP is a safe and effective alternative to anthracycline based chemotherapy though total dosage may be an important factor in the level of pCR.Table: see text