tumor is a new organism (neogrowth) formed by abnormal growth of clonality in a cell of a local tissue at the gene level due to various carcinogenic factors. Because this new organism is mostly space-occupying massive protrusions, also known as neoplasms (neoplasm).

　　 tumor tissue consists of cancer cells Qualitatively, cancer cells are abnormally proliferating cells transformed from normal cells. Tumors can occur in many organs and tissues of the human body. According to the size of tumors and their growth characteristics, they are divided into benign tumors and malignant tumors.

　　Tumor is at an early stage, local blood circulation is good, there are few hypoxic cells, and there are few normal tissues irradiated, which makes it easier to control. Conversely, in the late stage of the tumor, the local blood flow is poor, there are many hypoxic cells, and the sensitivity to radiation is low. There are many normal tissues to be included during radiotherapy, and the repair is poor and the efficacy is also poor.

　　The base of the tumor growth (cancer bed) is muscle, and the blood flow is good, so the radiotherapy effect is good. If the blood flow of the cancer bed is poor, and the site is not resistant to the radical dose, the effect is poor. For example, the local blood flow of cervical cancer is good, and the surrounding tissues such as the vagina and uterus are tolerant to radiation, so the radiotherapy effect is good, and the esophageal cancer is poor.

　　 Therefore, the type 4a tumor is still very serious.