20P - Targeting HER2 in patients with HER2-negative metastatic breast cancer with elevated serum levels of the HER2 extracellular domain and/or HER2-posit...

Date 07 May 2015
Event IMPAKT 2015
Session Welcome reception and Poster Walk
Topics Anti-Cancer Agents & Biologic Therapy
Breast Cancer, Metastatic
Translational Research
Presenter Christian Kurbacher
Citation Annals of Oncology (2015) 26 (suppl_3): 6-9. 10.1093/annonc/mdv115
Authors C.M. Kurbacher1, A. Quade1, G. Kunstmann2, S. Herz1, J.A. Kurbacher3, M.A. Warm4
  • 1Gynecologic Oncology, Gynecologic Center Bonn-Friedensplatz, 53111 - Bonn/DE
  • 2Internal Medicine (hematology/oncology), Krankenhaus Holweide, 51067 - Köln/DE
  • 3General Obstetrics And Gynecology, Gynecologic Center Bonn-Friedensplatz, 53111 - Bonn/DE
  • 4Center Of Breast Diseases, Krankenhaus Holweide, 51067 - Köln/DE

Abstract

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Background: A considerable proportion of patients (pts) with HER2-negative (HER2-) metastatic breast cancer (MBC) present with elevated serum levels of the HER2 extracellular domain (sHER2) and/or HER2 overexpressing circulating tumor cells (CTCs) during their further clinical course. These “occult” HER2-positive (HER2+) pts may be candidates for anti-HER2 therapy (Tx) albeit normally not subjected to such treatment. This observational study was undertaken to gain more insights into the feasibility of HER2-directed Tx in pts with tissue HER2- MBC with elevated sHER2 levels and/or HER2+ CTCs in the clinical routine.

Methods: 25 pts with heavily pretreated HER2- MBC (ER + , n = 21) showing sHER2 values > 15 ng/mL (n = 6), HER2+ CTCs (n = 6), or both (n = 13) were included. sHER2 was determined by a commercial chemiluminescence immunoassay (Siemens Healthcare Diagnostics, Eschborn, Germany), CTCs were detected by using the CellSearchTM technology (Veridex, Raritan, NJ). Pts had failed 2-16 prior systemic treatments (median: 7). All pts received anti-HER2 Tx with trastuzumab (H: n = 13), lapatinib (L: n = 4), H + L (n = 2), or H + pertuzumab (H + P: n = 6). HER2-targeting Tx was given alone (n = 4), or in combination with endocrine agents (n = 4), cytotoxics (n = 16), or other targeted drugs (n = 1). Responses were scored according to RECIST 1.1, OS was calculated from the start of HER2-directed Ctx until death from any reason or loss to follow-up by using Kaplan-Meier statistics.

Results: Anti-HER2 Tx was generally well tolerated. Median treatment duration was 14.6 wks (range 1.0-56.1 wks). In 2 pts with L and 1 pt with H + L, Tx was prematurely stopped due to toxicity (diarrhea, fatigue). Whereas 5 pts progressed on Tx, 10 pts achieved PR and another 10 pts showed SD accounting for an objective response rate (ORR) of 40% and a rate with benefit (RWB) of 80%. Median OS was 62.9 wks.

Conclusion: Our findings indicate that anti-HER2 Tx may be a valid option in pts with heavily pretreated HER2- MBC with pathological sHER2 values and/or HER2+ CTCs in the clinical routine. Thus, results of ongoing randomized trials in this setting are eagerly awaited.

Disclosure: All authors have declared no conflicts of interest.