Lung cancer is the leading cause of death among the tumors in the whole world. Although new diagnostic techniques have been developed for nearly 20 years, the mortality is still high. Until now, no randomized controlled trial of chest x-ray and sputum cytology showed the improvement of the survival rate of lung cancer. Low-dose CT can screen more patients in early stage, however, overdiagnosis, cost and the quality of studies should be considered. Further studies of RCTs should be done to clarify these questions.
