年年体检正常，为啥还是得了癌症？

Core Viewpoint - The article discusses the complexities and limitations of cancer screening, emphasizing that not all screening methods are effective and that many can lead to false positives and false negatives [1][2][3]. Group 1: Limitations of Current Screening Methods - Effective cancer screening should improve survival rates, but many existing methods do not meet this standard [2][4]. - False negatives (missed tumors) and false positives (incorrectly identified tumors) are significant issues in cancer screening, leading to unnecessary anxiety and financial burden [7][8]. - Many commonly used tumor markers are not recommended for healthy individuals due to high rates of false results [7][10]. Group 2: Recommended Screening Methods - Recommended screening methods include colonoscopy for colorectal cancer, gastroscopy for gastric cancer, low-dose spiral CT for high-risk lung cancer, mammography and ultrasound for breast cancer, and cytology and HPV testing for cervical cancer [8][11]. - The age at which screening should begin varies by cancer type, with guidelines suggesting starting at 45 for colorectal cancer and 40 for breast cancer [11][12]. Group 3: Future Directions in Cancer Screening - There is ongoing research into new screening methods, including liquid biopsies that detect cancer-related DNA in blood and the use of artificial intelligence for early tumor detection through imaging [12][13].