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Women with lower levels of serum selenium (Se) may have a worse survival in breast cancer than women with higher levels, despite no difference in incidence of the disease. Our study was conducted to test whether Se is associated with the aggressiveness of breast tumors. Both the risk of having a tumor characteristic associated with worse prognosis, as well as the overall and breast cancer-specific mortality, were studied. We identified breast cancer cases and controls within the Malmö Diet and Cancer Study, a population-based cohort with 17 035 women recruited between 1991 and 1996. Inclusion criteria were incident breast cancer. Exclusion criteria were carcinoma in situ and bilateral breast cancer. Controls were selected among breast cancer-free women both from matching (n = 694) as well as randomization (n = 492). After exclusion, 1066 cases remained and were compared to controls regarding their prediagnostic serum Se levels and subsequent risk of having a certain tumor characteristic or intrinsic subtype. We also followed breast cancer patients regarding overall and breast cancer-specific mortality, comparing different Se quartiles. No association between serum Se quartile and any tumor characteristic or intrinsic subtype was found. Lower overall mortality was found among women in the highest Se quartile compared to the lowest using an adjusted Cox proportional hazards model, hazard ratio 0.63 (95% confidence interval: 0.44-0.89). Similar results were seen for breast cancer-specific mortality, 0.60 (0.37-0.98). The results of our study support that Se is associated with a lower mortality in breast cancer, not related to established prognostic factors., (© 2020 The Authors. International Journal of Cancer published by John Wiley & Sons Ltd on behalf of UICC.)

Clinical trials examining insulin-like growth factor-I receptor (IGF1R)-targeting strategies have emphasized that better predictive biomarkers are required to improve patient selection.Immunohistochemical tumor-specific protein expression of IGF1R, insulin receptor (InsR), and phosphorylated IGF1R/InsR (pIGF1R/InsR) individually and combined in relation to breast cancer prognosis was evaluated in a population-based cohort of 1,026 primary invasive breast cancer patients without preoperative treatment diagnosed in Sweden. IGF1R (n = 923), InsR (n = 900), and pIGF1R/InsR (n = 904) combined cytoplasmic and membrane staining was dichotomized. IGF1Rstrong/InsRmod/strong/pIGF1R/InsRpos tumors were borderline associated with 2-fold risk for events, HRadj (2.00; 95%CI 0.96-4.18). Combined IGF1R and pIGF1R/InsR status only impacted prognosis in patients with InsRmod/strong expressing tumors (Pinteraction = 0.041). IGF1Rstrong expression impacted endocrine treatment response differently depending on patients' age and type of endocrine therapy. Phospho-IGF1R/InsRpos was associated with lower risk for events among non-endocrine-treated patients irrespective of ER status, HRadj (0.32; 95%CI 0.16-0.63), but not among endocrine-treated patients (Pinteraction = 0.024). In non-endocrine-treated patients, pIGF1R/InsRpos was associated with lower risk for events after radiotherapy, HRadj (0.31; 95%CI 0.12-0.80), and chemotherapy, HRadj (0.29; 95%CI 0.09-0.99). This study highlights the complexity of IGF hetero-and homodimer signaling network and its interplay with endocrine treatment, suggesting that combinations of involved factors may improve patient selection for IGF1R-targeted therapy.