Open Access Research

Topoisomerase II alpha gene amplification is a favorable prognostic factor in patients with HER2-positive metastatic breast cancer treated with trastuzumab

George Fountzilas1*, Christos Christodoulou2, Mattheos Bobos3, Vassiliki Kotoula34, Anastasia G Eleftheraki5, Ioannis Xanthakis1, Anna Batistatou6, George Pentheroudakis7, Nikolaos Xiros8, Irene Papaspirou9, Anna Koumarianou8, Pavlos Papakostas10, Dimitrios Bafaloukos11, Dimosthenis V Skarlos2 and Konstantine T Kalogeras112

  • * Corresponding author: George Fountzilas fountzil@auth.gr

  • † Equal contributors

Author Affiliations

1 Department of Medical Oncology, “Papageorgiou” Hospital, Aristotle University of Thessaloniki School of Medicine, 564 03, Thessaloniki, Macedonia, Greece

2 Second Department of Medical Oncology, “Metropolitan” Hospital, Athens, Greece

3 Laboratory of Molecular Oncology, Hellenic Foundation for Cancer Research, Aristotle University of Thessaloniki School of Medicine, Thessaloniki, Greece

4 Department of Pathology, Aristotle University of Thessaloniki School of Medicine, Thessaloniki, Greece

5 Section of Biostatistics, Hellenic Cooperative Oncology Group, Data Office, Athens, Greece

6 Department of Pathology, Ioannina University Hospital, Ioannina, Greece

7 Department of Medical Oncology, Ioannina University Hospital, Ioannina, Greece

8 Oncology Section, Second Propaedeutic Department of Internal Medicine, University General Hospital “Attikon”, Athens, Greece

9 Histopathology Department, “Alexandra” Hospital, Athens, Greece

10 Department of Medical Oncology, “Hippokration” Hospital, Athens, Greece

11 First Department of Medical Oncology, “Metropolitan” Hospital, Athens, Greece

12 Translational Research Section, Hellenic Cooperative Oncology Group, Data Office, Athens, Greece

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Journal of Translational Medicine 2012, 10:212  doi:10.1186/1479-5876-10-212

Published: 23 October 2012

Abstract

Background

The vast majority of patients with HER2-positive metastatic breast cancer (MBC) treated with trastuzumab eventually develop resistance to this agent. There is an unmet need therefore, for identifying biological markers with possible prognostic/predictive value in such patients. The aim of this study was to investigate the prognostic role of topoisomerase II alpha gene (TOP2A) amplification and protein (TopoIIa) expression in patients treated with trastuzumab-containing regimens.

Methods

Formalin-fixed paraffin-embedded tumor tissue samples were retrospectively collected from 225 eligible patients treated with trastuzumab. Protein expression of ER, PgR, Ki67, PTEN, HER2 and TopoIIa were centrally assessed by immunohistochemistry. HER2 and TOP2A gene amplification was evaluated by fluorescence in situ hybridization. PIK3CA mutations were identified by single nucleotide polymorphism genotyping. Survival was evaluated from the initiation of trastuzumab as 1st line treatment to the date of last follow-up or death.

Results

Among the 225 samples analyzed, only 137 (61%) were found to be HER2-positive. TOP2A was amplified in 41% and deleted in 16% of such tumors. TOP2A gene amplification was more frequent in ER-negative tumors. TopoIIa protein expression was observed in the majority (65%) of the samples and was associated with ER-positive status, high Ki67 expression, presence of PTEN protein and PIK3CA mutations. Median follow-up for patients treated in the 1st line was 51 months. Survival was more prolonged with trastuzumab-containing treatment in HER2-positive patients (50 months, log-rank, p=0.007). TOP2A non-amplified or deleted tumors were associated with increased risk for death compared to TOP2A amplified tumors (HR=2.16, Wald’s p=0.010 and HR=2.67, p=0.009, respectively). In multivariate analysis, a significant interaction of TOP2A with anthracycline treatment (either in the adjuvant or the 1st line setting) was observed for survival (Wald’s p=0.015). Among the TOP2A amplified subgroup, anthracycline-treated patients were associated with decreased risk for death.

Conclusions

TOP2A gene amplification was shown to be a favorable prognostic marker in HER2-positive MBC patients treated with trastuzumab, such an effect however, appears to rather be related to treatment with anthracyclines (predictive marker for benefit from anthracyclines). The results of the present retrospective study warrant validation in larger cohorts of patients treated in the context of randomized trials.

Keywords:
Breast cancer; Topoisomerase II alpha; Fluorescence in situ hybridization; Gene amplification; Trastuzumab; Prognostic factors; Anthracyclines; Predictive factors