Acta oncologica
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Adjuvant tamoxifen therapy approximately halves the risk of recurrence in estrogen receptor-positive (ER+) breast cancer patients, but many women respond insufficiently to therapy. Expression of multi-drug resistance protein 2 (MRP2) in breast cancer may potentiate tamoxifen resistance. Thus, we investigated the expression of MRP2 in breast cancer as a predictor of tamoxifen therapy effectiveness. ⋯ MRP2 expression is neither a predictive marker of tamoxifen effectiveness nor a prognostic marker in breast cancer.