Abstract
Early diagnosis of cancer is a pressing issue to reduce the mortality rate. Advances in technology for analysis of trace components since the late 1980s have contributed to realizing differences in the quantity of volatile organic compounds (VOCs) in exhaled breath between cancer patients and healthy subjects, meaning that exhaled breath may be applied for early diagnosis of carcinoma. This review describes the generation mechanisms of oncogenesis and VOCs with carcinogenesis in exhaled breath, and the techniques of measurement and evaluation for VOCs in breath. While gas chromatography - mass spectrometry is often employed for analyzing VOCs in exhaled breath, recently techniques using soft ionization have also been applied. Each of measured VOCs is evaluated using various statistical and data processing techniques for biomarker identification. Various aliphatic and aromatic hydrocarbons and aldehydes have been identified as common biomarkers for carcinoma, and other types of VOCs have also been determined. Recently, sensor arrays or electronic nose technologies with pattern recognition for exhaled VOCs, which are in the early stage of practical application, have allowed to discriminate cancer patients from healthy subjects without identifications of each substance. Further research for discrimination methods with breath will ensure the early diagnosis method for carcinoma as an alternative to conventional methods.
