Volatomic pattern of breast cancer and cancer-free tissues as a powerful strategy to identify potential biomarkers

Breast cancer (BC) is ranked as the fifth amongst all cancers remaining at the top of women’s cancers worldwide followed by colorectal, lung, cervix, and stomach cancers according to the GLOBOCAN series of the International Agency for Research on cancer (IARC), contributing to more than 11.6% of all cancers.1 Although BC is a multifactorial disease, with highly variable clinical behavior and response to therapy, it can be curable in early stages. Furthermore, there is still the need for the development of new methodologies to aid or monitor the disease together with the current diagnostic tools, namely mammography, ultrasound or tumor markers. Moreover, before BC treatment, a complex and time-consuming analysis is required that uses many different assays, such as the determination of histological type and grading and the evaluation of estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER-2), among others.2 The main handicap of most of these screening/diagnostic methods is their low sensitivity and specificity and the invasive procedure required to obtain the samples.3 Taking into account these aspects, research is being directed towards the use of new tools that can support the clinicians in BC treatment and follow-up.4 In this sense, in recent years, metabolomic studies have emerged as a powerful tool to investigate the changes and/or metabolic responses of living systems to stimuli or genetic modifications.5 The metabolome profile represents the unbiased quantitative and qualitative analyses of the complete set of metabolites present in cells, body fluids and/or tissues.6 To date, beyond the most used biological specimens (e.g. urine, saliva, blood), BC tissues have been used in metabolomics with the aim of discriminating cancer from normal tissues suggesting that metabolomic profiles differ within molecular subtypes of BC.7,8 The metabolome