289P - A retrospective population-based observational study in metastatic HER2-positive breast cancer patients in Denmark previously treated with T-DM1

Background

Current Danish guidelines in HER2-positive metastatic breast cancer (mBC) recommend the combination of trastuzumab with one of several chemotherapeutic agents for 3^rd line or later treatments. This study aims to describe treatment of HER2-positive mBC in 3^rd line or later after previous treatment with T-DM1 for mBC in a Danish real-world setting.

Methods

This observational population-based study included all women diagnosed with HER2-positive mBC in Denmark, previously treated with T-DM1. Patients were included on the date of progression leading to subsequent initiation of 3^rd line treatment if the patient received T-DM1 in 1^st or 2^nd line. If the patient received T-DM1 in 3^rd line or later the inclusion was based on the date of progression on T-DM1. Inclusion dates were between 1^st of January 2014 and 31^st of December 2019. The primary end points were overall survival (OS) and progression-free survival (PFS).

Results

The study included 272 women with a mean age of 59 (range 27-86) and a median of 3 (range 2-11) lines of treatments prior to inclusion. All patients had received T-DM1 and 168 (62%) patients had received pertuzumab in the metastatic setting. Metastatic sites included bone (66 %), lung (53%), liver (51%) and CNS (13%). Following inclusion 183 patients received chemotherapy. Of these patients, 120 received chemotherapy combined with trastuzumab, 50 received chemotherapy combined with other HER2-targeted therapy and 13 received chemotherapy as monotherapy. The remaining 89 patients received either HER2-targeted monotherapy (41), endocrine therapy (31), experimental (10), or no treatment (7). Median PFS was 5.5 months (95% CI, 4.8-6.5) and median OS was 18.5 months (95% CI, 16.2-21.3).

Conclusions

In this real-world study, patients were treated with a wide variety of anti-cancer agents in 3rd line or later in HER2-postive mBC. These agents show efficacy in these pretreated patients, but there is still a need for effective therapies in the 3^rd line or later treatment settings.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

Danish Breast Cancer Group.

Funding

AstraZeneca.

Disclosure

A. Due: Financial Interests, Personal, Funding, Unrestricted Research Grant: Danish cancer society. T. Berg: Financial Interests, Institutional, Funding: Danish Cancer Society; Financial Interests, Institutional, Funding: Neye Fonden; Financial Interests, Institutional, Funding: Roche; Financial Interests, Institutional, Funding: Novartis; Financial Interests, Institutional, Funding: Samsung Bioepis; Financial Interests, Institutional, Funding: Pfizer; Financial Interests, Institutional, Funding: AstraZeneca; Financial Interests, Institutional, Funding: Merck Eisai; Financial Interests, Institutional, Funding: Venture Oncology; Financial Interests, Personal, Invited Speaker: Pfizer; Financial Interests, Personal, Advisory Board: Merck. M. Jensen: Financial Interests, Institutional, Funding: Samsung Bioepis; Financial Interests, Institutional, Funding: Nanostring Technologies; Financial Interests, Institutional, Funding: Venture Oncology. A. Knoop: Financial Interests, Institutional, Funding: Roche; Financial Interests, Personal, Advisory Board: Novartis; Financial Interests, Personal, Advisory Board: AstraZeneca; Financial Interests, Personal, Advisory Board: MDS; Financial Interests, Personal, Advisory Board: Roche; Financial Interests, Personal, Advisory Board: Pfizer; Financial Interests, Personal, Advisory Board: Eli Lilly Danmark A/S. K.K. Andersen: Financial Interests, Personal, Full or part-time Employment: AstraZeneca. S. Rana: Financial Interests, Personal, Full or part-time Employment: Daiichi Sankyo ApS. All other authors have declared no conflicts of interest.