1.The concept of tumor heat therapy Tumor heat therapy (hyperthermia) is a method of applying various heat sources combined with modern medical technology to heat up malignant tumors. Some scholars call it “warm heat treatment of cancer”, “high heat treatment of cancer”, “heat penetration treatment of cancer” and so on. In terms of heat therapy itself, it is a purely physical treatment, with heat sources including high frequency electromagnetic waves, infrared rays, ultrasonic waves, hot water baths and so on. When heating up the body, due to the unsound tissue structure of tumor tissues, the heat dissipation is slower than normal tissues, so that the temperature of tumor tissues is 5℃～10℃ higher than normal tissues, while malignant tumor cells are sensitive to high heat, as a result, tumor cells are killed or gradually apoptotic after high heat, while normal tissues are not damaged. The unique advantage of thermotherapy compared with radiotherapy and chemotherapy is that it has no toxic side effects. At the same time, thermotherapy can enhance the immune ability of the body, increase the efficacy of radiotherapy and chemotherapy, reduce tumor recurrence, improve the quality of survival of tumor patients and prolong the survival period. 2.Origins of thermotherapy for tumors The word thermotherapy originated from Greek, meaning high heat or overheating. The history of heat therapy in the West can also be traced back to 5,000 years ago, when Egyptian doctors used the heating method to treat breast tumors. The ancient Greek doctor Hippocrates (460-370 BC, the father of medicine) also used heat therapy to treat tumors. He had a motto: “What cannot be cured by drugs can be treated by surgery, what cannot be cured by surgery can be cured by heat therapy, and what cannot be cured by heat therapy cannot be cured”. Since 1866, some patients with malignant tumors have been reported to have tumor regression due to occasional dengue, severe infection or history of hyperthermia. Later on, scholars have reported cases in which heat combined with other therapies improved the efficacy of tumors or cured them. Tumor heat therapy has not made greater progress from the ancient fire needles, moxibustion, branding iron and medicinal bath to the whole body heat therapy using infected dermatophytosis in the 19th century, and it was not until the 1980s that it began to be truly applied in clinical practice, which has been a long journey of several thousand years. Nowadays, thermotherapy has developed into an independent discipline. Although this discipline is still imperfect, it will go through the same naive and immature stage as other means of tumor treatment, and judging from the current efficacy of thermotherapy in many therapeutic areas, it will eventually become a very promising therapeutic tool. Since there are many mechanisms and multiple biological effects of thermotherapy that have not been fully grasped, its efficacy characteristics are completely different from traditional radiotherapy and chemotherapy, which has attracted strong attention from many medical clinical scholars, biologists, bioengineers, immunologists, and physicists, and they have invested in the research of corresponding fields, which has laid a good development foundation for the development of thermotherapy. In the 1980s, although tumor thermotherapy was clinically applied, there was a lack of basic biological research; although the field of biology was involved, the treatment all belonged to the stage of understanding at the physical level; the initial application in combination with radiotherapy had got good efficacy, but the application in combination with drugs and other therapies was not observed; the equipment used was primitive, similar to physiotherapy machines, and the application of intracavitary microwave, single-source rotary ultrasound and 13.56 MHz radiofrequency equipment. At present, Shanghai Oriental Hospital applies more advanced 8 MHz radiofrequency tumor heat therapy machine (RF8), which is safe and reliable and has better effect. Research shows that high heat can directly kill tumor cells and inhibit the synthesis of deoxyribonucleic acid (DNA), ribonucleic acid (RNA) and protein; high heat can damage the normal function of cell membrane, change the permeability of cell membrane, cause protein overflow and change the structure of nuclear chromatin, resulting in the death of cancer cells. . Because the internal structure of tumor tissues is not sound, the respiration of tumor cells is inhibited during hyperthermia, and the enhanced anaerobic enzymolysis causes the pH to drop, which in turn strengthens the activity of lysosomes and causes the tumor cells to lyse and die; the inhibition of protein synthesis also inhibits the proliferation of tumor cells and causes them to die. All these are most sensitive to the S phase of cell proliferation, which can be tens to hundreds of times different from other phases. This is because radiation therapy and many drugs are effective against cell proliferation cycles beyond the S phase. Such a complementary and synergistic relationship has important therapeutic value in clinical practice. (2) Heat therapy increases the effect of chemotherapy Studies have shown that 42°C in vitro for 120 minutes can enhance the cancer-killing effect of some chemotherapy drugs by 10 to 100 times. In clinical practice, the combined application of heat therapy and chemotherapy is far more effective than the sum of the two therapeutic effects. In the case of achieving the same efficacy index, the dosage of chemotherapy drugs can be reduced, thus reducing the harm to human body. (3) Heat therapy increases the effect of radiotherapy Heat therapy and radiotherapy have different sites of action in the cell proliferation cycle, i.e. the cell cycle sensitive to heat therapy is not sensitive to radiotherapy treatment, so that a complementary relationship is formed, and heat therapy changes the histological and physiological properties of the tumor at the same time, and these can enhance the effect of radiotherapy. (4) Heat therapy affects the immunity of the body In the special biological characteristics of tumor tissues have different responses from normal tissues, which results in accelerating the death of tumor tissues. (5) Heat therapy eliminates toxins from the body The human skin provides protection for the whole body, and it is both an absorbing and excreting organ. During the whole body heat therapy, the human body discharges a large amount of sweat, and the pores that normally cannot be opened will be opened to the maximum extent, while a large amount of sweat is discharged, the toxic substances absorbed by the body and skin will be discharged, which makes the body free from the stimulation of toxic substances and achieves the purpose of disease prevention. (1) Whole-body thermotherapy refers to the method of heating all parts of the body to make the body temperature rise evenly and achieve the treatment temperature. There are three kinds of heating methods, i.e., heating by body surface, extracorporeal circulation method and biological method (no longer used). Body surface heating can be divided into infrared radiation heating, microwave heating, etc., while the hot water bath, hot wax bath, electric blanket, etc. used in the 1980s has been no longer applied due to a number of defects. At present, infrared radiation heating is really effective, with small side effects, easy to monitor and low cost, and is more often used in clinical practice. External circulation force heating refers to the method of using special equipment to pump part of the blood out of the body for heating to a predetermined temperature, and then instill it into the body to reach the treatment temperature, but it is not easy to be popularized because of the expensive equipment and cost. Biological method refers to the method of heating the body with biological agents, which is not easy to control the temperature and time, and is no longer used. (2) Regional thermal therapy is a method that heats a part of the body in a larger range than local heating. Heating methods include microwave, radiofrequency, regional thermal perfusion, etc. Since regional heating can also raise the temperature of the whole body, some scholars are now using regional heating for whole-body heat therapy. RF8 deep tumor heat therapy machine has the advantage of 13 cm heating, high temperature, deep site, good patient tolerance and no adverse reaction. (3) Local heat therapy The heating range is limited to the lesion and a small part of the surrounding normal tissues, and the whole body temperature does not increase significantly. Heat sources include microwave, radiofrequency, ultrasound, etc. Microwave is more used in early local heat therapy. Local heat therapy is suitable for many kinds of superficial tumors, such as superficial lymph node metastasis, skin cancer, malignant melanoma and other tumors in superficial parts of the body. 5.The organic combination of heat therapy and radiotherapy, i.e., thermal radiotherapy The organic combination of local heating and precise radiotherapy for the treatment of tumors with significantly improved side effects is a new treatment technology called thermal radiotherapy (referred to as thermal radiotherapy) (1) Mechanism of action Clinically, heat therapy is often used in combination with radiotherapy, and heat therapy can sensitize radiotherapy, and its mechanism of action may have the following aspects: Heat therapy increases the oxygen content of cells around the tumor and prevents hypoxia from weakening the effect of radiotherapy. It prevents hypoxia from weakening the effect of radiotherapy, because radiotherapy is sensitive to oxygenated tumor cells; the hypoxic area in the tumor center is sensitive to thermotherapy but not to radiotherapy. The cell proliferation phase (S phase) is resistant to radiotherapy and sensitive to thermotherapy; the mitotic phase (M phase) is sensitive to radiation and insensitive to thermotherapy, thus forming a complementary relationship. Heat therapy inhibits the repair of cellular DNA in tumor tissues after radiotherapy, while radiotherapy can reduce the heat tolerance of tumor cells, thus forming a complementary relationship as well. The research on the combination of thermotherapy and radiotherapy in the treatment of tumors has a history of several decades, and the clinical application has achieved encouraging results. The latest research results confirm that thermoradiotherapy has synergistic effects, sensitizing effects and maximum cytotoxic effects. (2) Indications for thermal radiotherapy Applicable to tumors in all parts of the body except intracranial tumors, including: superficial tumors: breast cancer, skin cancer, malignant lymphoma, soft tissue sarcoma, etc. Deep tumors: lung cancer, esophageal cancer, gastric cancer, liver cancer, intestinal cancer and various metastatic cancers. Intrapelvic tumors: gynecological tumors, prostate cancer, rectal cancer, etc. (3) Precautions for thermal radiotherapy ① It is normal to feel hot at the treatment site during the treatment, and the patient thinks it is best to feel the heat most comfortably. Strong heat sensation is relatively effective, but it is easy to burn, so patients should not bear it. ②The overly obese will have subcutaneous pain and fatty hard knots, the incidence is about 1%. Even if these conditions occur, they can be absorbed and healed by themselves after a few weeks without special treatment. The patient should wear cotton clothes and pants, and remove all metal and magnetic objects (such as watches, belts, cell phones, lighters, rings, necklaces, etc.) from the body to avoid burns.