Prospective analysis of pre-diagnostic untargeted plasma metabolomics and risk of triple-negative breast cancer in the European Prospective Investigation into Cancer and Nutrition (EPIC)

Triple-negative breast cancer (TNBC) accounts for 10–15% of newly diagnosed breast cancer, and its aetiology is poorly understood compared to other breast cancer subtypes. We applied untargeted metabolomics to identify novel biological pathways associated with TNBC risk and potentially distinct from those related to hormone receptor–positive breast cancer risk. Using an untargeted ultra-high-performance LC–MS method, we measured molecular features of pre-diagnostic plasma samples from 1:1 matched nested case-control pairs of TNBC ( n = 271 cases and n = 271 controls) and oestrogen and progesterone-positive receptor breast cancer (ER + PR+) ( n = 271 cases and n = 271 controls) within the EPIC cohort. From a total of 3135 molecular features detected in positive and negative configurations of the LC-MS, 1801 features were retained after data pre-processing and imputation. Conditional logistic regression was used to estimate odds ratios (ORs) and false discovery rate (FDR)-adjusted confidence intervals (CIs) for molecular features and risks of TNBC and ER + PR+. In nominal analyses, 85 molecular features were associated with TNBC risk, of which 34 were positively associated, and 51 were inversely associated with the risk (raw p-value < 0.05). However, no features were statistically significant after FDR correction. When comparing TNBC with ER + PR+ breast cancer risk, 69 molecular features discriminated TNBC from ER + PR+ subtypes (P heterogeneity < 0.05). Of these, 8 metabolites could be annotated. Specifically, higher levels of tyrosine were associated with a lower risk of TNBC (OR = 0.79, 95% CI = 0.63–0.99 per 1 SD increase), while hexadecenoylcarnitine, octenoylcarnitine, uric acid, a bilirubin photodegradation product and 2-hydroxy-3-methylbutyric acid were associated with a higher risk of ER + PR+ breast cancer, and caffeine and 2-furoylglycine with a lower risk of ER + PR+ breast cancer. This study highlights a set of metabolites nominally associated with TNBC risk, although none of these metabolites reached statistical significance after FDR correction. These findings suggest that metabolic pathways related to tyrosine, uric acid, acylcarnitines, bilirubin, 2-hydroxy-3-methylbutyric acid, caffeine and 2-furoylglycine may help distinguish the risk of TNBC from ER + PR+ breast cancer. Fifteen unannotated metabolites also emerged as suggestively associated with TNBC risk and seem to be related to inflammatory pathways. Additional studies are required to replicate these findings and to annotate these unannotated features. Not applicable.