| Carcinoma of the lung has been the leading cause of cancer death in China for decades. No certain results have been given on the mechanism of its development. Tobacco use especially cigarette smoking has been recognized as a major risk factor for nearly 50 years. Extensive and worldwide epidemiological investigations have provided evidence for the causal role of tobacco in lung cancer, yet little attention has been given on other risk factors of lung cancer. However, despite the fact that tobacco smoke is the culprit for over 80% of current lung cancer occurrence, only 7-10% of all lung-term heavy smokers will develop this disease. It indicates that besides tobacco smoking, theremight be some other risk factors that play important roles in the development of lung cancer. Individual susceptibility to carcinogen exposures is indisputable, and the familial aggregation of lung cancer also suggested that inherited genes may be important in the development of lung cancer. In lung cancer a wide range of genetic alterations have been reported among tumor suppressor genes, oncogenes, and DMA mismatch repair genes, and loss of heterozygosity has been found from more than 10 different chromosomal arms. However it is difficult to distinguish the genes playing a role in cancer susceptibility, and the inherited susceptibility to lung cancer therefore needs a further investigation.Passive smoking, occupational exposure to carcinogen, air pollute, diet and cooking smoke are regarded as risk factors of lung cancer, but they all acted as carcinogen exposures. Up to date, no major steps were taken in the researching of susceptibility to lung cancer.A previous history of non-neoplastic disease including asbestosis, silicosis, tuberculosis and pneumonia had been reported to increase lung cancer risk in 1980', and a positive association of lung cancer with asthma, allergies has been reported inconsistently. In the meantime, in our clinical work, lung function damage has been found in many lung cancer patients who presented lower FEV1% and emphysema on X ray film, even dyspnea. Professor Ping Yang in Mayo Clinic reported the COPD might be a risk factor of lung cancer, the development of lung cancer might be related to the functional status of the lung.As an initial step to verify this hypothesis, the lung cancer risk factors among population in Xi'an was investigated in the present study.The analysis of lung cancer risk factors was based on the data of a case-control study conducted during 1999-2001 in Xi'an, China, and correlation power of all the risk factors and lung cancer was evaluated by the odd ratio (OR). The results indicated that tobacco smoking, air pollutes, cooking smoke, history of previous lung diseases, family history of tumor, family history of lung cancer and psychic trauma were the main risk factors of lung cancer, however, physical practice and fresh vegetables were the protective factors.To further investigate the relationship between history of previous lung diseases and lung cancer, patients with different lung diseases and the risk of lung cancer were analyzed. The results show that the patients with Chronic Obstructive Pulmonary Diseases (COPD) had an increased risk of lung cancer. Furthermore, the impairment of lung function was observed to increase the risk of lung cancer.COPD is the only group of chronic pulmonary non-malignant diseases that share a common etiology with lung cancer. Earlier studies suggested that lung cancer and COPD could both be due to cigarette smoking. The relationship between COPD and the risk of lung cancer was affected by smoking, therefore, COPD could not be distinguished as an independent risk factor for lung cancer. However, our study demonstrated that even in nonsmokers the risk of lung cancer in people with COPD is higher than those without COPD. Furthermore, people with a family history of COPD will be a candidate to have an increased risk of lung cancer. All of these evidence suggest a possibility of having a common genetic factors and /or pathological...
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