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RESEARCH PRODUCT

Outcomes of single versus double hormone receptor–positive breast cancer. A GEICAM/9906 sub-study

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Abstract Background Retrospective data suggest better outcomes for patients with double hormonal receptor (oestrogen [ER] and progesterone receptor [PgR])–positive (dHR+) early breast cancer, compared with single hormonal receptor–positive, sHR+, (ER+/PgR– or ER–/PgR+) disease. Here, we evaluate the classification according to intrinsic subtypes and clinical outcomes of sHR+ versus dHR+ in HER2-negative breast cancer patients enrolled in GEICAM/9906 study ( NCT00129922 ). Methods Archival tumours were retrieved retrospectively for the analysis of ER, PgR and HER2 status and classified into intrinsic subtypes using the PAM50 gene expression assay. Disease-free survival (DFS) and overall survival (OS) were explored using a Cox proportional hazard analysis. Results Data on intrinsic subtypes were available in 571 (50%) patients with ER+ and/or PR+, and HER2-negative primary tumours. The incidence of luminal A and luminal B subtypes were 52%/36% in dHR+ tumours (ER+/PgR+), and 15%/58% in ER+/PgR–tumours. ER–/PgR+ tumours were mainly luminal A (52%). Compared with ER+/PgR+ patients, DFS was similar in ER–/PgR+ (hazard ratio [HR] 1.15, 95% confidence interval [CI] 0.57–2.34, p = 0.70) but worse in ER+/PgR– patients (HR 1.60, 95% CI 1.12–2.28, p  Conclusions The ER+/PgR– group is characterised by higher proliferation and worse outcomes. In spite of the ER–/PgR+ subgroup resembles ER+/PgR+ disease in terms of molecular subtypes and outcomes, the small number of patients in this subgroup prevents from drawing any conclusions. Trial registration EudraCT: 2005-003108-12 (retrospectively registered 28/06/2005). Clinicaltrials.gov Identifier NCT00129922 (retrospectively registered 10/08/2005).