• Håvard Søiland, Ivar Skaland, Jan Erik Varhaug, Hartwig Kørner, JanssenEmiel A MEA, Einar Gudlaugsson, BaakJan P AJP, and Jon Arne Søreide.
• Department of Surgery, Stavanger University Hospital, Norway.
• Acta Oncol. 2009 Jan 1; 48 (4): 514-21.

BackgroundEstrogen receptor-alpha (ERalpha) is an important prognostic and predictive marker in breast cancer. ERalpha signaling normally down-regulates expression of Apolipoprotein D (ApoD), a lipocalin that binds, transports or chelates lipophilic ligands, including tamoxifen (TAM). Hence, the co-expression of ApoD may therefore identify clinical relevant subgroups of ERalpha positive breast cancer patients.Material And MethodsApoD, ERalpha, and progesterone receptor (PR) protein expressions were determined by immunohistochemistry (IHC) in primary tumors of 290 patients with operable breast cancer. The median follow-up was 12 years. Patients were stratified according to age, nodal stage and the expression of ERalpha and the combined cytoplasm and nuclear staining of ApoD (ApoD(CN)).ResultsIn elderly women (> or =70 years) (n = 76), ApoD(CN) expression identified different prognostic subgroups in ERalpha positive patients (Trend: p < 0.0001). Multivariate analysis in this age group (n = 72), showed that the ERalpha-positive /ApoD(CN)-negative subgroup had a better breast cancer specific survival (BCSS) compared with the ERalpha-positive/ApoD(CN)-positive group (hazard ratio (HR) = 4.3; 95% CI = 1.6-11.9; p = 0.005). This difference was predominantly seen in the node positive patients (n = 30) (HR = 10.5; 95% CI = 2.3-47.6; p = 0.002). In a subset of postmenopausal ERalpha-positive/node positive patients (n = 60) previously enrolled in a trial on 2 year adjuvant TAM 20 mg vs. placebo, a better BCSS was observed in ApoD(CN) negative patients compared to placebo (p = 0.02). In ApoD(CN) positive patients, adjuvant TAM did not provide any survival benefit.DiscussionERalpha and ApoD(CN) co-expression seems to be of prognostic importance in node positive elderly patients with operable breast cancer. In addition, we hypothesize that ApoD(CN) expression may be a novel marker and/or mechanism of TAM resistance in postmenopausal node positive patients. Thus, when targeting the ERalpha pathway in these patients, the ApoD status of the tumor may be of clinical relevance.

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