In the recent years, scientific interests in searching of non-invasive, painless and patients friendly technique for which would facilitate diagnosis early-stage cancer without necessary using invasive medical routine has been increased. An exemplary solution could be e.g. analysis of breath which has numerous advantages in comparison with traditional diagnostic methods. Volatile organic compounds (VOCs) are generated by the human body as products of metabolic process. However, biochemical methods for creation of the most of compounds, which were detected in breath, have not been precisely explain from the scientific point of view. Chemical analysis of breath composition may help to identify potential markers, that could be applied for the cancer early diagnosis in the near future. For determination of VOCs present in human breath have been applied solid phase microextraction (SPME) or thermal desorption (TD) and gas chromatography-mass spectrometry (GC/MS and GCxGC-MS/MS/MS). These techniques are used for the extraction, separation and determination of analytes present in trace amounts at the level of parts per million by volume - parts per trillion by volume (ppmv-pptv). The most promising one are coupled to mass spectrometry with ionization in selected ion flow (SIFT-MS), the reaction proton-transfer mass spectrometry (PTR-MS), ion mobility spectrometry (IMS), sensor technology and electronic nose. An innovative, unconventional method applied was the dog smell to detect changes in carcinoma. Dogs after suitable training were able to indicated with high sensitivity and specificity samples of exhaled air at patients with breast, lung, melanoma, ovarian and bladder cancer. Analyzing obtained data by trained dogs should be noted good agreement of the disease detection, which is in the range between 80-90% for lung and breast cancer. In the future using canine olfactory one can find application for screening of cancer.

Acknowledgment
This work was supported by the National Science Centre (NCN, Warszawa, Poland) projects No. 2013/08/W/NZ8/701 – Symfonia-1 and Maestro-6 (2015-2017)