Treatment principles of radiotherapy for gastric cancer Gastric cancer is a tumor that is not sensitive to radiation, while the neighboring organs of stomach, such as liver, pancreas and kidney, are more sensitive to radiation, thus limiting the application of radiation therapy in gastric cancer. As one of the means of comprehensive treatment, radiotherapy can be used in conjunction with surgery to improve the radical rate, help eliminate subclinical metastases in the operative field, and palliative treatment for residual or recurrent gastric cancer. Preoperative radiotherapy is more frequently used in radiotherapy for gastric cancer and its efficacy is more certain, which can increase the surgical resection rate by 5%-14%, radical resection rate by 4%-20% and 5-year survival rate by 70-14%. In principle, surgery should be performed 2 weeks after the end of radiotherapy, not too early, but no later than 3 weeks. Intraoperative radiotherapy helps to clear subclinical lesions in the irradiated field to improve the efficacy. If there are metastatic lymph nodes or cancer residues, 14-20 Mev electron wires can be used with a dosage of 35 Gy. For advanced cases that cannot be resected, the primary foci can be irradiated with 35-40 Gy at a time to relieve symptoms and prolong survival. Postoperative radiotherapy is often used after palliative resection of gastric cancer. For residual lesions or unresected metastatic lymph nodes, postoperative radiotherapy can be used after marking. High-energy radiation with a total dose of DT50~60Gy/6 weeks is used, and irradiation is usually started 3 weeks after surgery. Chemotherapy is the main part of drug treatment for gastric cancer. Pre-operative, intra-operative and post-operative chemotherapy can be used to improve surgical resection rate, reduce recurrence rate and improve survival rate. For advanced patients who are inoperable, relapsed after radical surgery or palliative resection, rerouting or exploration, chemotherapy is one of the main methods of comprehensive treatment. The commonly used chemotherapeutic agents for the treatment of gastric cancer include 5-Fu and its derivatives, MMC, ADM, and in recent years, PDD and VP-16 are often included in combination chemotherapy. Preoperative chemotherapy is feasible for patients with progressive gastric cancer that cannot be resected radically, such as 5-Fu 750mg + LV (calcium formyl tetrahydrofolate) 200mg for 3-5 days one week before surgery. Postoperative adjuvant chemotherapy after radical surgery for early gastric cancer is in principle not chemotherapy, but adjuvant chemotherapy in the following cases: pathological type with high malignancy; lesion diameter > Scm; lymph node metastasis; young patients. A single drug can be used after surgery. After radical surgery for progressive gastric cancer, all combined chemotherapy is used. If the wound heals well after surgery, chemotherapy can be started 3 to 4 weeks after surgery. Advanced gastric cancer chemotherapy patients who cannot be operated, non-radical surgery or relapse after surgery should adopt combined chemotherapy as the main comprehensive therapy with 1-2 months interval, and no less than 3 courses of chemotherapy in the first year. Side effects of chemotherapy for gastric cancer Chemotherapy for gastric cancer is extremely harmful to human body, so the use of chemical agents must be strictly tested. The most critical thing is to deal with the side effects of chemotherapy so as to ensure the best effect of gastric cancer treatment. 1. Decline of immune function: Chemotherapy drugs can damage the immune system of patients, resulting in deficiency or decline of immune function. Immune function indicators such as E-rose node test, CH50, C3 complement, T-cell subsets, NK cell activity, interleukin II, etc. may decrease in varying degrees after chemotherapy compared with before chemotherapy. Most antitumor chemotherapy drugs have immunosuppressive effects. 2.Weakness: Patients may suffer from weakness, depression, sweating, drowsiness, etc. 3.Inflammatory reaction: fever, dizziness, headache, dry mouth, sore mouth and tongue, etc. 4, digestive disorders: decreased appetite, reduced diet, nausea, vomiting, bloating, abdominal pain, diarrhea or constipation, etc. Many chemotherapy drugs trigger the above symptoms by stimulating the mucous membrane of the gastrointestinal tract. 5.Bone marrow suppression: Most chemotherapeutic drugs can cause bone marrow suppression, which is manifested as a decrease in white blood cells and platelets, or even a decrease in red blood cells and hematocrit. 6, nephrotoxicity: some chemotherapy drugs in high doses can cause renal impairment and back pain and discomfort in the kidney area. 7, cardiotoxicity: some chemotherapy drugs can produce cardiotoxicity, damage the heart muscle cells, patients appear panic, palpitations, chest tightness, anterior heart discomfort, shortness of breath and other symptoms, and even heart failure. The electrocardiogram may show T-wave changes or S-T segment changes, etc. 8, pulmonary fibrosis: isocyclophosphamide, vincristine, bleomycin, etc. can cause pulmonary fibrosis, fearing that the X-ray chest film can be seen in the lung texture increase thick or striped changes. It is more dangerous for patients with poor lung function in the past, and may even be life-threatening, etc. Types of chemotherapy for gastric cancer 1. Adjuvant chemotherapy. For some early gastric cancer, although radical resection has been performed, in order to avoid intraoperative dissemination and recurrence and metastasis caused by micro-metastases existing at the time of surgery, adjuvant chemotherapy should be administered early after surgery and be continued for about one year. Large lesions, which are reduced by chemotherapy and then operated on, also belong to this category, also known as neoadjuvant chemotherapy. 2.Treatment of lesions. Patients with lesions that cannot be treated surgically, or those with left supraclavicular lymph nodes and distant metastases, can be treated with chemotherapy. Patients with postoperative recurrence or metastasis are also in principle in this category. Effective cases can achieve control of lesions, reduce pain, improve quality of life and prolong survival time. Individual cases may also have complete regression of lesions. 3.Intracavitary treatment. Some patients with gastric cancer will have cancerous peritoneal effusion in advanced stage. Intraperitoneal injection of anti-cancer drugs can achieve higher local concentration than intravenous drugs. At this time, the relevant drugs can be injected into the peritoneal cavity after the abdominal fluid is pumped and released, in order to control the ascites. The effect of chemotherapy for gastric cancer: the above is a brief introduction of this issue, and the process of chemotherapy treatment for gastric cancer is a complicated process, which can cause great side effects to gastric cancer patients, therefore, for chemotherapy for gastric cancer, attention should be paid to the treatment of side effects after chemotherapy. How to take care of gastric cancer after chemotherapy 1. Psychological care: Before chemotherapy, explain to the patient the process of chemotherapy, loss of appetite, nausea and vomiting may occur. It should be tolerated and can heal itself in 2-3 weeks. Insist on completing chemotherapy. 2, diet care: encourage patients to choose high calorie, high protein, high vitamin, easy to digest food. And need to quit smoking and alcohol, if necessary, give appetizing and antiemetic drugs. As well as infusion, fat milk with amino acids, etc. 3, abdominal care: closely observe whether the patient has abdominal pain, diarrhea, abdominal pain, abdominal muscle tension and intestinal sounds, check whether the blood pancreatic amylase is elevated. 4.Blood picture observation: check the blood routine and platelets once every two weeks. If the white blood cell drops to 2*10 9/L, transfuse a small amount of fresh blood several times, and stimulate acupuncture points such as the foot three li and dazhi by electric acupuncture. If the white blood cell still does not rise, it is necessary to stop radiotherapy and take isolation protection measures for the patient. 5, skin care: irradiated field skin protection dry, forbidden to tape and use hot water bags, without soap scrubbing, with soft dressing protection, avoid scratching with hands, if it has been ulcerated, with exposure therapy, external application of rehabilitation new, forbidden to contain metal drugs. 6.Radiation pneumonia care: once it occurs, radiotherapy should be stopped immediately. Give high-dose antibiotics plus hormones. Give oxygen inhalation when breathing difficulty, keep the airway open, rest in semi-recumbent position.