Analysis Of Volatile Organic Compounds In The Exhaled Breath For The Diagnosis Of Lung Cancer

BackgroudLung cancer is the leading cause of cancer deaths worldwide among both men and women, with more than 1 million deaths annually.In 2012, there were 1.82 new cases globally, and 1.56 million deaths due to lung cancer, representing 19.4% of all deaths from cancer. The highest rates are in North America, Europe and East Asia, with over a third of new cases in 2012 in China. Clinical studies show that the cure rate for lung carcinoma in situ is nearly 100%,the 5 years survival rate for I stage lung cancer is 60%～90%,but the 5 years survival rate for Ⅲb stage and Ⅳ stage is only 5%～20%.The high mortalityof lung cancer is largely because in the majority of patients it is at an advanced stage at the time it is discovered, when curative treatment is no longer feasible.Thus in lung cancer, early detection is essential to improve survivability through identification and therefore treatment of patients before their cancers become inoperable and lethal.Currently, chest X-ray,CT scan and lung biopsy have been used in lung cancer diagnosis. Nearby lymph nodes can be tested for cancer cells with a procedure called a mediastinoscopy, while imaging techniques such as CT scans, PET scans, bonescans, and either an MRI or a CT scan of the brain can detect cancer elsewhere in the body. Although recent advances have been made in diagnosis and treatment strategies, the prognosis of lung cancer patients is poor and it is basically due to a lack of early diagnostic tools.A breath test is a type of test performed on air generated from the act of exhalation. Breath tests for diseases have been developed by companies for early detection of lung cancer, breast cancer, pulmonary TB and many others, to serve as an adjunct to existing medical tests. Phase II and Phase III clinical studies are under way to confirm the efficacy of these breath tests.In this study, the Model 4200Z-nose (electronic noses)has been used in detecting and analyzing vapors in breath,this ESTs high speed gas chromatography employs patented techniques to separate chemicals in near real time so that pattern recognition and trace detection can be performed in seconds. Unlike trace detectors which only detect a few select compounds, electronic noses recognize odors and fragrances based upon their full chemical signature.The purpose of the study is to use the Model 4200Z-nose to identify the volatile organic compounds(VOCs) in exhaled breath of lung cancer patients and healthy controls that appear to be associated with the disease, and build the prediction model of lung cancer by considering both the age and the VOCs.ObjectiveCompare the volatile organic compounds (VOCs) in exhaled breath between the patients with lung cancer and the healthy controls. To evaluate volatile organic compounds (VOCs) in the breath as tumor markers in lung cancer, exploring a noninvasive, rapid, sensitive, convenient and inexpensive diagnostic method for lung cancer screening.Methods(1) The two groups of the study:the test group includes 63 patients with pathology-confirmed lung cancer hospitalized in the first affiliated hospital of jinan university (Guangzhou);and the control group includes 72 healthy controls lived in Guangzhou City and the surrounding area (nocancer,diabetes, chronicrenal insufficiency,upper respiratory tract infection and other chronic diseases).The main sources of 72 healthy individuals are the family members of the 63 lung cancer patients, the medical staffs in the first affiliated hospital of jinan university, part of the staffs in the southern medical university and their families. At the same time, collect the basic information, such as age, sex, smoking statusof the all subjects, and the clinical data(including lung pathological type, clinical stage, metastatic sites, etc.)of the test group. During the selection of all the subjects, gender and smoking status were collected by a certain percentage, but age considerations as random.(2) The sampling procedures:We collected breath samples from 135 study objects by using the 1L Devex bags. The night before we collect the breath samples, all of the subjects must fasting for spicy foods and any foods with strong odor (such as pepper, wine, coffee, tea, garlic, leeks, onions, etc.). what’smore, the sampling procedures must be done in the morning in the case that the objects is fasting and without brushing.(3) The preparation methods of the associated detection reagents:the standard solution for instrument calibration(C6-C14 n-alkanes solution)was formulated by nine kinds of mixed organic solution (hexane, heptanes, octane, nonane, decane, undecane, dodecane, tridecane and tetradecane), and then diluted with methanol; the standard solution for instruments quantitative calculation(C6-C20 n-alkanes standard solution) was formulated by 13 kinds of organic solution (hexane, heptane, octane, nonane, decane, undecane, dodecane, tridecane, tetradecane, hexadecane, octadecane and eicosane).(4)The breath test procedures:The VOCs in the exhaled breath were determined qualitativelyand quantitatively by the Model 4200 Z-nose. After turn on and completion all the conditions set of theModel 4200 Z-nose, calibrate the horizontal axis retention indices (named kovats index, KI) of the chromatogram with C6-C14 n-alkanes solution, and then test all the gas samples.Finally,complete the quantitative calibration(the area under peak of the chromatograms) of the test results with C6-C20 n-alkanes standards.(5) The screening of VOCs:Analysis the test results of 135 gas samples detected by the Model 4200 Z-nose, select the VOCs in breath from the test group and the control group according the kovats index.(6) The statistical analysis of the results:R3.0.3 and IBM SPSS 19.0 software were used for the statistical analysis. The VOCs between the two groups were compared by Mann-Whitney U test, and the stepwise logistic regression analysis was used to select statistically significant variables to establish a prediction model for diagnosis of lung cancer. The receiver operating characteristic (ROC) curve was used to evaluate the predictive ability of this prediction model.ResultsTheconcentrations of dimethylmethane, ethanol methane, hexane, 2.2.4.6.6-pentamethylheptane,2.5.5-trimethyl-2.6-heptadien-4-one,l-isopropyl-4-met hylbicyclo[3.1.0]hexan-3-ol,dodecane and 1.2.6-trimethylnaphthalene in the exhaled breath of study group were significantly different from those of control group. A panel of biomarkers was selected to set up a decision tree as the prediction model: accuracy of 80.6% in study group and 83.9% in control group) with a sensitivity of 74% and a specificity of 93%.ConclusionsThe profile of VOCs in exhaled breath can reflect the metastatic status of cancer and specific medical conditions. The database concerning VOCs in the exhaled breath should be developed and may be helpful in diagnosis of lung cancer.