The present invention relates to a metabolic biomarker set for use in assessing breast cancer in a mammalian subject. In particular, the invention relates to a metabolic biomarker set for screening and/or diagnosing breast cancer, the metabolic biomarker set including at least (a) one amino acid selected from glutamine, glutamate and serine, and one lipid, or (b) glutamine and glutamate. Further, the invention relates to a metabolic biomarker set for prediction of therapeutic response to breast cancer neoadjuvant chemotherapy. Moreover, the present invention relates to a method for assessing breast cancer, which includes obtaining a biological sample, preferably blood, from a mammalian subject and measuring in the biological sample the amount and/or ratios of metabolites. By employing the specific biomarkers and the method according to the present invention it becomes possible to more properly and reliably assess breast cancer.