Abstract P4-13-20: Activity of HP-based therapies as third and later lines for the treatment of HER2-positive metastatic breast cancer: A retrospective study from a single institution

Abstract

Abstract Background: Dual anti-HER2 blockade with trastuzumab and pertuzumab (HP) plus chemotherapy is an effective therapy (Rx) in the 1st-line setting for HER2-positive metastatic breast cancer (MBC). Our single arm phase II study included patients (pts) treated with HP plus paclitaxel in the 2nd-line setting with progression-free survival (PFS) benefit. Recently, we reported results from a retrospective study of pts treated at our institution, suggesting a longer PFS for those who received HP-based Rxs when compared to any other anti-HER2 based Rxs in the 2nd-line setting. To further assess the activity of this combination in later Rx lines, we conducted a retrospective analysis of pts with HER2-positive MBC who had progressive disease after 2nd-line and were treated with HP-based Rxs in the 3rd and later lines at MSKCC. Historically, the median (med) PFS in this setting with trastuzumab-based Rx is about 3-4 months. Methods: Pts diagnosed with HER2-positive MBC and treated with HP-based Rxs at MSKCC between 1-1-2011 and 03-30-2015 and who progressed on 2nd-line Rx were identified through an institutional database. Primary endpoint was PFS in 3rd and later treatment lines. Results: 70 pts who received any HP-based Rx in the 3rd or later lines of treatment were eligible. The med number of prior anti-HER2 Rx was 3. The baseline characteristics and Rxs are summarized in Table 1. The med PFS for the entire cohort was 5.7 months (95% CI, 4.8-6.5). Conclusions: In this retrospective analysis involving heavly pretreated patients, HP-based Rx appears to be an active regimen and compares favorably to historical data. This supports the NCCN endorsement of HP-based Rx in later lines if HP has not been delivered previously. Baseline Characteristics and treatments (n=70)Characteristic(n)(%)Age Median56 Range27-83 Gender Female70100.0Male00.0Race Black1014.3White5477.1Other68.6Ethnicity Non Hispanic6694.3Hispanic45.7ER/PR status ER and PR negative2738.6ER and/or PR positive4361.4Type of disease Non visceral1622.9Visceral5477.1Visceral CNS2130.0Anti-HER2 in early stage Yes2941.4No4158.6Line of therapy 3rd line1927.14th line1521.45th line912.96th line912.97th line811.48th line and beyond1014.3HP-based regimens Chemotherapy + HP5477.1Endocrine therapy + HP57.1HP alone912.9Other22.9 Citation Format: Argolo D, Friedman M, Smyth L, Iyengar N, Singh J, Patil S, Norton L, Baselga J, Hudis C, Dang C. Activity of HP-based therapies as third and later lines for the treatment of HER2-positive metastatic breast cancer: A retrospective study from a single institution. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P4-13-20.