F21 - Trastuzumab Emtansine (T-DM1) in Patients (pts) With Human Epidermal Growth Factor Receptor 2 (HER2)-Positive Metastatic Breast Cancer (MBC): results From a Multicenter Retrospective Analysis

Abstract

Background: T-DM1 improved outcomes in pts with HER2+ MBC, but few data concerning its use in routine clinical practice are available. Patients and methods: We retrospectively enrolled 194 HER2+ (IHC 3+ or 2+ amplified) MBC pts treated with T-DM1 in real-world practice in 20 Italian oncologic centers. Results: Baseline pts and tumors characteristics are listed in Table 1. Median (m) follow up was 9.8 months (mo) (range,2-37), m T-DM1 treatment duration was 5 mo (range, 1-30). Among 183 evaluable pts, 5.4% had a complete response and 35% a partial response, for an Overall Response Rate of 40% (95%CI, 33-47). A stable disease (SD) was recorded in 26.8% pts, with a clinical benefit (CB: response or SD lasting ≥ 6 mo) of 55% (95%CI, 47-62). No significant differences in responses have emerged according to disease sites. M Progression Free Survival (PFS) was 6 mo (95%CI, 5-7), m Overall Survival (OS) was 35 mo (95%CI, 11-59). Pts who have previously carried out ≤3 lines for MBC had improved PFS (p = 0.006). At multivariate analysis, factors related to PFS benefit were lower ECOG performance status (PS) (p < 0.0001) and HER2+ status at first diagnosis (p = 0.03), while OS benefit was related with lower ECOG PS (p = 0.01), absence of brain metastases (p = 0.08), other than ductal histology (p = 0.04) and CB (p < 0.0001). Central nervous system (CNS) progression occurred in 10.4% of the pts without CNS metastases, and in 29.1% of the pts with CNS metastases at baseline. Pts with CNS metastases at baseline have a m PFS similar to that observed in the general population, whereas m OS was shorter (16 mo, C.I. 95%, 12-21). Toxicity was manageable, with grade ≥3 adverse events reported in 5.6% of pts, most commonly thrombocytopenia and fatigue. Cardiac dysfunction was reported in 2 pts (1%). Conclusion: In this real-world setting of heterogeneous HER2+ MBC pts, efficacy of T-DM1 was comparable with that reported in phase II-III studies. No new safety issues were observed.Table: F21Main baseline characteristics of the study participants (N = 194)CharacteristicsN (%)AgeMedian (range)56 (34-82)HystologyDuctal173 (89.2)Lobular11 (5.7)Other10 (5.1)GradingG255 (28.4)G3124 (63.9)Unknown (Uk)15 (7.7)Metastatic at diagnosisYes47 (24.2)No147 (75.8)HER2+ at diagnosisYes157 (80.9)No25 (12.9)Uk12 (6.2)ECOG PS097 (50)163 (32.5)29 (4.6)31 (0.5)Uk24 (12.4)Previous regimen for MBC010 (5.2)140 (20.6)247 (24.2)≥397 (50) Open table in a new tab