Abstract PS10-37: Real-world experience of patients treated for HER2-positive metastatic breast cancer at the centre hospitalier universitaire de Quebec: A retrospective cohort study
Authors: Douville Vincent , Desbiens Christine , Théberge Valérie , Blanchette Caty , Lemieux Julie 
Published: February 2021

Abstract
Introduction: Multiple HER2-targeted therapies are now available and have significantly altered the natural course of HER2-positive metastatic breast cancer (mBC), with overall survival (OS) now exceeding 4 years. However, patients with HER2-positive mBC represent a heterogeneous population with some patients presenting with a history of a localized cancer and some with de novo metastatic disease. Our aim was to study the outcomes of HER-positive mBC in a real-life setting and compare the evolution between patients with “recurrent” breast cancer compared to those with “de novo” disease. Methods: In this single-center, retrospective study, we included patients with HER2-positive mBC treated at the Centre hospitalier universitaire (CHU) de Quebec using the local cancer registry and patients’ medical charts. We included all female patients &gt; 18 years of age who received one or more anti-HER2 therapy for mBC. Patients whose follow-up at our center was incomplete were excluded. We identified patients who developed mBC after the occurrence of a localised disease (“Recurrent” group) and patients diagnosed with metastatic disease upon first presentation (“De novo” group). Primary outcome was OS. Secondary outcomes were progression-free survival (PFS) for each line of treatment and for each type of treatment (trastuzumab [T], pertuzumab [P], lapatinib [L] and trastuzumab emtansine [T-DM1]). We performed survival analysis using the Kaplan-Meier method and the log rank test. Results: A total of 106 patients in the Recurrent group and 58 patients in the De novo group were identified between May 2002 and December 2018 and data were collected between March and June 2019, by which time 97 (59.1%) had died. There were differences in baseline characteristics between the Recurrent and the De novo groups regarding age at first metastasis (50.7 vs 57.4 years, p=0.001). A total of 44.3 % vs 32.8 % of patients developed brain metastasis respectively (p=0.15). There was no statistical difference between the two groups regarding OS (3.8 years for Recurrent vs 4.2 years for De novo, p=0.17). PFS were also similar between the 2 groups for every anti-HER2 treatment available during the study period (Table 1). Median PFS could not be established for P in the De novo group since 80 % of patients were censured at the time of data collection. In the Recurrent group, P, L and T-DM1 had median PFS at least as long as those reported in landmark clinical trials. PFS were also similar between groups when comparing treatment lines (Table 2). Conclusion: In this retrospective study of patients from a real-world setting, anti-HER2 therapies offered similar OS between HER2-positive mBC patients with recurrent disease and with de novo metastatic disease. Median PFS are also equivalent between groups, with durations in the range of the PFS reported in major RCTs.
Table 1TreatmentRecurrent groupRecurrent groupDe novo groupDe novo groupP valuenMedian PFS (years)nMedian PFS (years)Trastuzumab741.7441.90.14Pertuzumab333.115-0.15Lapatinib290.7110.60.17T-DM1310.7120.70.52
Table 2LineRecurrent groupRecurrent groupDe novo groupDe novo groupP valuenMedian PFS (years)nMedian PFS (years)1sd1061.6582.00.142nd490.7200.60.273rd230.990.70.794th100.430.80.53
Citation Format: Vincent Douville, Christine Desbiens, Valérie Théberge, Caty Blanchette, Julie Lemieux. Real-world experience of patients treated for HER2-positive metastatic breast cancer at the centre hospitalier universitaire de Quebec: A retrospective cohort study [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS10-37.