APC and lung cancer: Based on eligible studies published in full text, the results showed that the methylation of the P16, RASSF1A, APC or SHOX2 genes were significantly associated with lung cancer in the bronchial aspirates, suggesting that the test of methylated P16, RASSF1A, APC or SHOX2 using bronchial aspirates could serve as potential noninvasive biomarkers in lung cancer.