Abstract P1-18-28: Myocet or carboplatin as part of chemotherapy in HER2-positive operable breast cancer treated with trastuzumab and pertuzumab in the neoadjuvant setting: Efficacy data and cardiotoxicity in 60 patients diagnosed from 2016-2019 at a single institution

Objectives: To evaluate the efficacy and cardiotoxicity profile of liposomal anthracycline or Carboplatin as part of neoadjuvant therapy added to taxanes and dual blockade in HER2-positive operable breast cancer patients. Methods: A total of 60 patients diagnosed from August 2016 to May 2019 were included in the study. The treatment consisted of a sequential regimen of taxanes and non- pegilated liposomal anthracycline (Myocet) plus trastuzumab and pertuzumab, or taxanes in combination with carboplatin plus trastuzumab and pertuzumab. The clinical and pathologic responses were evaluated and correlated with clinical and biological factors. Pathologic complete response was defined as the total absence of invasive tumor in both breast and axillary nodes (ypT0/is ypN0).The cardiotoxicity profile was also analyzed. Results: The median age was 52(26-77) years and 5%, 62% and 33% of patients had stage I, II and III breast cancer, respectively, while 7% had inflammatory breast cancer at diagnosis. Hormone receptor (HR) status was negative in 48%, and 65% and 50% had grade III and ki-67 value up to 35%, respectively breast cancer. 65% of patients received weekly paclitaxelx12-trastuzumab-pertuzumab followed by Myocet-cyclophosphamide with -trastuzumab x 4 cycles or this sequence but beginning with the anthracycline, 23% of patients the same regimen but with pertuzumab concurrently with all chemotherapy treatment. The remaining 12% received docetaxel-carboplatin x6 cycles plus trastuzumab and pertuzumab. All treatment was administered previous surgery. The clinical complete response rate, was 57% and 63%, as assessed using ultrasound and MRI, respectively, and this allowed a high rate of conservative surgery (60%). The pathologic complete response (pCR) rate was 52%, and it was higher in HR-negative (61%) than in HR-positive (39%), in grade 3 (71%) than in grade 2(29%) tumors. There were not statistical significant differences in pCR between different chemotherapy treatments. Five patients showed a 10% decrease in left ventricular ejection fraction (LVEF) to below 50% at the end of neoadjuvant treatment. Asymptomatic drops in 2 patients and with heart failure symptoms in 3 of them. Myocet was part of chemotherapy in all of them. All patients recovered after discontinuation of adjuvant trastuzumab and heart medication. Two of these patients did not complete all preplanned adjuvant trastuzumab doses. Conclusion: A sequential regimen of taxanes and non-pegilated liposomal anthracycline or carboplatin plus trastuzumab and pertuzumab was effective, with high pCR rates and a good cardiotoxicity profile. Citation Format: Silvia Antolin, Cristina Reboredo, Rocio Lesta, Aurea Molina, Joaquin Mosquera, Patricia Cordeiro, Eva Perez, Lourdes Calvo. Myocet or carboplatin as part of chemotherapy in HER2-positive operable breast cancer treated with trastuzumab and pertuzumab in the neoadjuvant setting: Efficacy data and cardiotoxicity in 60 patients diagnosed from 2016-2019 at a single institution [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P1-18-28.