Abstract P3-09-07: Prognostic value of immunophenotypically defined subtypes in patients treated with dose-dense sequential adjuvant chemotherapy in the trastuzumab era. A Hellenic Cooperative Oncology Group study

Abstract

Abstract Background-Aim: The aim of the present study was to explore the efficacy of dose-dense sequential adjuvant chemotherapy followed by trastuzumab in HER2-positive patients according to the immunohistochemically (IHC) defined subtypes. Patients and methods: A total of 771 formalin-fixed paraffin-embedded (FFPE) tumor tissue samples, prospectively collected from 990 eligible patients with high-risk N0 or N1 operable breast cancer participating in a phase III trial (HE10/05), were centrally assessed in tissue microarrays by IHC for 6 biological markers, that is, estrogen receptor (ER), progesterone receptor (PgR), HER2, Ki67, cytokeratin 5 (CK5) and EGFR. All cases were further evaluated for HER2 amplification by FISH. Patients were classified as: luminal A (ER/PgR-positive, HER2-negative, Ki67low, N=382, 49.5%); luminal B (ER/PgR-positive, HER2-negative, Ki67high, N=136, 17.6%); luminal-HER2 (ER/PgR-positive, HER2-positive, N=125, 16.2%); HER2-enriched (ER-negative, PgR-negative, HER2-positive, N=63, 8.2%); triple-negative (TNBC) (ER-negative, PgR-negative, HER2-negative, N=65, 8.4%); and basal core phenotype (BCP) (TNBC, CK5-positive and/or EGFR-positive, N=53, 6.9%). Results: At a median follow-up of 60.5 months, the 3-year disease-free survival (DFS) and overall survival (OS) rates for the total patient population were 88.3% and 96.0%, respectively. The 3-year DFS rates for luminal A, luminal B, luminal-HER2, HER2-enriched, TNBC and BCP patients were 91.1%, 88.2%, 86.4%, 93.7%, 87.7%, and 89.4%, respectively, while the corresponding 3-year OS rates were 95.8%, 95.6%, 97.6%, 95.2%, 95.4%, and 95.0%, respectively. No significant differences were detected for either 3-year DFS or OS in the immunohistochemically defined subtypes, except a trend for significantly worse DFS in patients with luminal-HER2 tumors compared to patients with HER2-enriched tumors (log-rank, p=0.069). Conclusions: In the post-trastuzumab era, at a relatively short follow-up, the luminal-HER2 patients show a trend for worse DFS compared to patients with HER2-enriched tumors treated with dose-dense sequential adjuvant chemotherapy followed by trastuzumab. No other significant differences were detected, with follow-up however being continued. Citation Format: George Fountzilas, Eleni Timotheadou, Georgia Gourgioti, Petroula Arapantoni-Dadioti, Sotiris Lakis, Anna Batistatou, Triantafyllia Koletsa, Olympia Tzaida, Mattheos Bobos, Alexandra Papoudou-Bai, Eleftheria Tsolaki, Sofia Chrisafi, Elena Fountzilas, Ioannis Efstratiou, Helen Gogas, Flora Zagouri, Dimitrios Pectasides. Prognostic value of immunophenotypically defined subtypes in patients treated with dose-dense sequential adjuvant chemotherapy in the trastuzumab era. A Hellenic Cooperative Oncology Group study [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P3-09-07.