Lactate in exhaled breath condensate and its correlation to cancer: challenges, promises and a call for data

Owing to its connection to cancer metabolism, lactate is a compound that has been a focus of interest in field of cancer biochemistry for more than a century. Exhaled breath volatile organic compounds (VOCs) and condensate analyses can identify and monitor volatile and non-VOCs, respectively, present in exhaled breath to gain information about the health state of an individual. This work aims to take into account the possible use of breath lactate measurements in tumor diagnosis and treatment control, to discuss technical barriers to measurement, and to evaluate directions for the future improvement of this technique. The use of exhaled breath condensate (EBC) lactic acid levels in disorders other than cancer is also discussed in brief. Whilst the use of EBC for the detection of lactate in exhaled breath is a promising tool that could be used to monitor and screen for cancer, the reliability and sensitivity of detection are uncertain, and hence its value in clinical practice is still limited. Currently, lactate present in plasma and EBC can only be used as a biomarker for advanced cancer, and therefore it presently has limited differential diagnostic importance and is rather of prognostic value.