The battle with tumor is never easy, once a wrong step is taken, the subsequent goes into passivity. How fast a patient’s tumor grows actually varies from person to person, partly depending on the mutated genes of the tumor itself, and partly on the immune power of the patient. Of course, there are still some indicators that can be used to partially reflect the growth rate of tumors. The tumor cells keep dividing and proliferating, which is reflected in the CT image as the tumor lesions keep increasing in size. Of course, the tumor cells themselves are also dying, mainly due to the attack of drugs and immune system, the competition of tumor cells themselves and so on. After the apoptosis of tumor cells, their DNA and cell contents are released into the blood, which is the circulating tumor DNA (ctDNA), and this is also the principle of blood sampling for tumor gene mutation. So sometimes a lesion that looks unchanged on CT may already have extensive necrosis, etc. How many tumor cells are actively proliferating? What is the percentage? If this value is larger, it often means that the tumor is growing faster, more aggressive, and the prognosis is not particularly good.