The serum composition, as far as the endogenous metabolites are considered, could be remodeled due to such host-tumor interactions. At first glance they could be considered as direct leakages of cancer cells metabolites but recent reports suggest that host response to cancer is also important even at early stages. Moreover, the origin of these systemic metabolic modifications remains a subject of debates. However, because of the considerable diversity of these results, BC metabolomics remain exploratory. Many studies have shown significant alterations in the plasma or serum of BC patients. Metabolomics, the global qualitative and quantitative evaluation of metabolites in a biological system, by NMR spectroscopy, mass spectrometry or combined techniques has emerged as a unique tool to investigate the modification of metabolites of cancer cells or in biofluids and tissues of cancer patients. So there is an obvious need for a better understanding of BC biology. However, despite progresses in therapies and supportive cares of advanced diseases, the majority of relapsing patients die of the malignancy or its complications. Mortality rate has declined over the last decades mainly due to advances in screening methods, leading to earlier diagnosis, and successful multidisciplinary treatments of the early diseases. If confirmed in a lager study these observations could be of clinical importance.īreast cancer (BC) is the most common diagnosed cancer and the leading cause of cancer death in women worldwide, accounting for 25% of all cancer cases and 15% of all cancer deaths among females. We suggest that, in BC patients, tumor cells could induce modulation of the whole patient's metabolism even at early stages. In particular lactate levels are inversely correlated with the tumor size in the EBC cohort (Pearson correlation r = −0.309 p = 0.044). Using Principal Component Analysis, Partial Least-Squares Discriminant Analysis and Hierarchical Clustering we show that plasma levels of glucose, lactate, pyruvate, alanine, leucine, isoleucine, glutamate, glutamine, valine, lysine, glycine, threonine, tyrosine, phenylalanine, acetate, acetoacetate, β-hydroxy-butyrate, urea, creatine and creatinine are modulated across patients clusters. We evaluated by 1H-Nuclear Magnetic Resonance ( 1H-NMR) spectroscopy, filtered plasma metabolome of 50 early (EBC) and 15 metastatic BC (MBC) patients. Alterations in the serum metabolome of BC patients have been identified but their clinical significance remains elusive. There is an obvious need for a better understanding of BC biology. Breast cancer (BC) is the most common diagnosed cancer and the leading cause of cancer death in women worldwide.