Tumor radiotherapy is a kind of local treatment method that uses radiation to treat tumors.Radiation includes alpha, beta, gamma rays produced by radioisotopes and x-rays, electron wires, proton beams and other particle beams produced by various x-ray therapeutic machines or accelerators.About 70% of cancer patients need radiotherapy in the process of cancer treatment, and about 40% of cancer can be cured by radiotherapy.Radiation therapy plays an increasingly prominent role in tumor treatment and has become one of the main means to treat malignant tumors.
Although radiotherapy has a history of only a few decades, it has developed rapidly.With the help of the development of CT imaging technology and computer technology, the current radiotherapy technology has developed from two-dimensional radiotherapy to three-dimensional radiotherapy and four-dimensional radiotherapy. The radiotherapy dose distribution has also developed from point dose to volume dose distribution, and the dose intensity modulation in volume dose distribution.Current mainstream radiotherapy technologies include stereotactic radiotherapy (SRT) and stereotactic radiosurgery (SRS).Stereotactic radiotherapy (SRT) includes three-dimensional conformal radiotherapy (3DCRT) and three-dimensional intensity modulated radiotherapy (IMRT);Stereotactic radiosurgery (SRS) includes X-knife, Y-knife and CyberKnife. X-knife, gamma knife and CyberKnife are all part of stereotactic radiotherapy. SRS is characterized by three-dimensional, field, cluster, fractional and high-dose irradiation. It requires higher positioning accuracy and faster dose decay outside the target area.
The curative effect of radiotherapy depends on the radiosensitivity. Different tissues and organs as well as various tumor tissues have different degrees of response to changes after irradiation.Radiosensitivity is related to the proliferation cycle and pathological grading of tumor cells, that is, the cells with active proliferation are more sensitive than those without proliferation. The higher the degree of cell differentiation, the lower the radiosensitivity, and vice versa.In addition, the oxygen content of tumor cells directly affects the radiosensitivity. For example, if the tumor is small in early stage and has good blood supply, the curative effect is good when there are few hypoxic cells; if the tumor is large in late stage and has poor blood supply in the tumor, even if there is necrosis in the center, the radiosensitivity is low;The local squamous cell carcinoma has better blood circulation and higher sensitivity than the tumors in buttocks and limbs;The tumor was locally associated with infection, poor blood circulation (more hypoxia cells), and decreased radiosensitivity.Therefore, keeping the irradiation site clean and preventing infection and necrosis are important conditions to improve the radiosensitivity.The sensitivity of radiation to tumor can be divided into:
1. Radiation sensitive tumor
The tumor disappeared after 20-40 Gy irradiation, such as lymphoid tumor, seminoma, nephroblastoma, etc;
2. Radiation moderately sensitive tumor
60~65Gy of irradiation is needed to eliminate tumors, such as most squamous cell carcinoma, brain tumor, breast cancer, etc;
3. Low radiosensitivity tumor
It means that the tumor disappears only after irradiation of more than 70Gy. For example, for most adenocarcinoma, the radiosensitivity of the tumor is related to the degree of cell differentiation. The higher the degree of differentiation, the lower the radiosensitivity;
4. Radiation insensitive (resistant) tumor
Such as fibrosarcoma, osteosarcoma, melanoma, etc.
However, some poorly differentiated tumors, such as reticular cell sarcoma of bone, Ewing sarcoma, fibrosarcoma, retroperitoneal liposarcoma and popliteal liposarcoma, can still be considered for radiotherapy.
indication
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According to different types of tumors in various systems, the indications for current treatment can be divided into the following categories:
1. Digestive system
Early surgery for oral cancer has the same effect as radiotherapy, and some parts are more suitable for radiotherapy, such as tongue root cancer and tonsil cancer.Preoperative radiotherapy is better for medium-term comprehensive treatment.Palliative radiotherapy can be used in late stage.Esophageal cancer is mainly treated by surgery in the early stage and radiotherapy in the middle and late stage. In addition, cervical and upper thoracic esophageal cancer is generally treated by radiotherapy due to the difficulty of surgery and poor quality of life after surgery.Surgical treatment is mainly used for liver, pancreas, stomach, small intestine, colon and rectum cancer.Surgical treatment of colorectal cancer may be more beneficial than radiotherapy.The efficacy of intracavitary radiotherapy for early rectal cancer is the same as that of surgery.Radiotherapy for liver and pancreatic cancer has a certain palliative effect.
2. Respiratory system
Nasopharyngeal carcinoma is mainly treated with radiotherapy.Preoperative radiotherapy is better for maxillary sinus cancer.Some patients who cannot be operated can be cured by radiotherapy alone.Early radiotherapy or surgery for laryngeal cancer, and combined radiotherapy and surgery for intermediate and late stage cancer.Lung cancer is mainly caused by surgery. Those who are not suitable for surgery and have no distant metastasis can be treated by radiotherapy, and a few can be cured.Small cell undifferentiated lung cancer needs radiotherapy plus chemotherapy.
3. Urogenital system
Renal clear cell carcinoma is mainly operated, and postoperative radiotherapy has certain benefits.In the early stage of bladder, surgery is the main method. In the middle stage, radiotherapy before surgery has certain benefits. In the late stage, palliative treatment can be used.The combination of surgery, surgery, radiotherapy and chemotherapy is the best treatment for nephroblastoma.The testicular tumor should be operated first, and then treated with postoperative radiotherapy.The effect of early surgery and radiotherapy for cervical cancer is the same. For stage II or above, only radiotherapy can be used, and the effect is good.Preoperative radiotherapy is better for uterine body cancer. Those who cannot be operated can also be treated with radiotherapy.
4. Breast cancer is mainly treated by surgery
For stage I or stage II breast cancer, if the tumor is located in the lateral quadrant and the axillary lymph node is negative, postoperative radiotherapy is not required. For stage I breast cancer, if the tumor is located in the medial quadrant or stage II breast cancer, postoperative radiotherapy is required.Stage III preoperative irradiation is also beneficial.For early breast cancer, radiotherapy was performed on the breast and lymphatic drainage area after "breast conserving surgery", and the effect was also very good.
5. Nervous system tumor
Most brain tumors require postoperative radiotherapy.Medulloblasts should be mainly treated with radiotherapy.Radiotherapy or chemotherapy should be performed after the operation of neuroblastoma.Pituitary tumor can be treated with radiotherapy or postoperative radiotherapy.
6. Malignant tumor of skin and soft tissue
The skin and mucosa (including penis and lip) can be treated with surgery or radiotherapy in the early stage, or radiotherapy in the late stage;Melanoma and other sarcomas should be mainly operated.It can also be considered to cooperate with radiotherapy.
7. Malignant tumor of bone
Osteosarcoma is mainly operated, and preoperative radiotherapy can also be used.Reticulocyte sarcoma and Ewing tumor of bone can be treated with radiotherapy and chemotherapy.
8. Lymphoid tumor
Stage I and II are mainly radiotherapy, stage III and IV are mainly chemotherapy, and local radiotherapy can be added.
contraindication
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There are few absolute contraindications to radiotherapy, especially low palliative treatment, such as pain relief for local metastases.However, it also depends on the conditions of the patient and the unit. Generally speaking, when patients with advanced tumors are in cachexia, it can be regarded as an absolute contraindication to radiation.In addition, esophageal cancer perforation, lung cancer with a large amount of cavity effusion should also be listed as an absolute contraindication.
Any tumor that is not sensitive to radiation should be regarded as a relative contraindication, such as skin melanoma, stomach cancer, small intestine cancer, soft tissue sarcoma, osteochondrosarcoma, etc.Generally, postoperative radiotherapy is supplemented after surgery.
Acute inflammation and heart failure should be controlled before radiotherapy.
Radiotherapy is not suitable for lung cancer when large area of radiation is needed and the lung function is seriously incomplete.
