A nationwide observational study in heavily pretreated metastatic HER2-positive breast cancer patients

Asbjørn Due*, Tobias Berg, Maj-Britt Jensen, Sophie Yammeni, Lone Volmer, Anne Sofie Brems-Eskildsen, Klaus Kaae Andersen, Saeeda Rana, Ann Knoop, Iben Kümler

*Corresponding author for this work


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

MATERIAL AND METHODS: This observational population-based study included all women diagnosed with HER2-positive mBC in Denmark, previously treated with T-DM1 in the metastatic setting. Patients were included on the date of progression leading to initiation of 3rd line treatment if the patient had received T-DM1 in 1st or 2nd line. If the patient received T-DM1 in 3rd line or later the inclusion was based on the date of progression on T-DM1. 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 (27-86) and a median of 3 (2-11) treatment lines prior to inclusion. At index, all patients had received T-DM1 and 167 (62%) patients had received pertuzumab in the metastatic setting. During follow-up 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 treatment (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).

CONCLUSION: In this real-world study, we found that patients were treated with a wide variety of anti-cancer agents with modest efficacy. However, patients in this study did not have access to newer therapies like tucatinib and T-DXd.

Original languageEnglish
JournalActa Oncologica
Issue number2
Pages (from-to)126-133
Number of pages8
Publication statusPublished - Mar 2023


  • Ado-Trastuzumab Emtansine
  • Adult
  • Aged
  • Aged, 80 and over
  • Antineoplastic Combined Chemotherapy Protocols/therapeutic use
  • Breast Neoplasms/pathology
  • Female
  • Humans
  • Maytansine/adverse effects
  • Middle Aged
  • Receptor, ErbB-2
  • Trastuzumab/therapeutic use


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