Whether or not fasting is needed for cancer screening depends on which cancers are being screened, such as gastrointestinal tumors, most of which require fasting, such as gastroscopy, colonoscopy, CT scan with enhancement or magnetic resonance examination. Blood sampling for tumor markers does not necessarily require fasting, and if the lung CT examination can also be done without fasting. Others, such as breast ultrasound is also important for breast cancer screening and can be done without fasting, and thyroid ultrasound is also not related to diet. Therefore, the need for fasting for cancer screening is somewhat related to the items being examined. Digestive tract tumors need to be examined on an empty stomach, tumor markers can be examined without fasting, and there is no fasting requirement for other lung and thyroid tumor examinations.