Quality Assurance for Hyperthermia in Cervical Lymph Node Metastasis of Nasopharyngeal Carcinoma
|School||Guangzhou Medical College|
|Keywords||Nasopharyngeal carcinoma radiotherapy chemotherapy thermotherapy microwave applicator specific absorption rate|
Background ObjectiveThrough practices, it has been known that heat can be used in treating the superficial tumor since ancient times. The expression“Hyperthermia”is from Greek, meaning of which is the high fever or overheated .In the 19th and the 20th century, numerous scholars reported that high fever had a certain therapeutic effect on tumor, even had the possibility to cure certain malignant tumor. With the emergence of X-ray treatment machine and the widespread use of the chemotherapy, heat was started to use combing with radiotherapy and chemotherapy to treat various types of tumor, which received some more satisfactory results. In recent years, people have carried on mass of observations to the tumor thermotherapy, and gained many experiences. They gradually realize that quality assurance of thermotherapy became the most important. A satisfactory thermotherapy target area (tumor lesion) must be covered in effective warming area completely. How to know whether the tumor is covered in the effective warming area? Will the temperature inside the tumor achieve the expectation value? How about the efficiency of the applicator? Is it isothermal area large enough to the big tumor? Would the applicator’s efficiency still the same, when it had been used for a period of time? Is the heating efficiency the same with another similar one? Therefore, before the thermotherapy, we must measure and compare the efficiency of the applicator to ensure thermal therapeutic quality.Objective 1. The aim of the study was to analyze the curative effect of thermotherapy combined with radiotherapy and chemotherapy on patients with cervical lymph node metastases of nasopharyngeal carcinoma.2. Analyze the effect of microwave applicator’s specific absorption rate (SAR) distribution.Material and Methods1.Clinical analyzing 67 patients who were nasopharyngeal carcinoma with large cervical lymph node metastases(according to TNM Classification of nasopharyngeal carcinoma Fuzhou, China, 92 by staging up to N2-N3) were enrolled and randomly divided into experimental group(n=35) and control group (n=32). Microwave hyperthermia combined with radiation therapy and chemotherapy (HT+RT+CT)were performed in the experimental group and control group just with radiation therapy and chemotherapy(RT+CT).Radiation treatment was using 6Mv-X-ray, the dosage to the cervical lymph nodes were 60-75Gy/30-33fractions. Chemotherapy was started from the 2th week , in which patients were given DDP 20mg d1-5, 5-Fu 750mgd1-5. The treatment was repeated every 3 weeks for two cycles. Using single node invasive thermocouple probes to measure cervical lymph node’s temperature, cervical lymph nodes were heated by a 915MHz microwave thermotherapy machine. Patients were given hyperthermia 4-8 times on average for 45 min immediately after radiotherapy.2.Applicator measuring Microwave thermotherapy machine use 200w power, applicator is away from the phantom model’s surface 1cm and 2cm, heats up 5 minutes and 7 minutes continually. Hot sensitive fluid epitaxial and the optical fiber temperature measurement system are used to measure the Jianghanbao muscle formula phantom model respectively. Record the color changes of heat sensitive fluid epitaxial and the temperature of optical fiber obtain in each minute, draw out applicator’s SAR distribution. Compare the change of the temperature when continual heating, analyze when applicator in different distance how is the SAR distribution change. Results1.35 patients received radiotherapy and chemotherapy combined with hyperthermia (RT+CT+HT) and 32 patients received radiotherapy and chemotherapy (RT+CT), The complete response (CR) rate was 65.7% in the experimental group but 40.6% in the control group . The CR rates in the N2 and N3 patients was 79.6%, 30.8% respectively in the experimental group but 52.2%,11.1% in the control group. The are no significant difference between two groups on skin reaction of radiation.2. Applicator is away from phantom model 1cm, heats up 1 minute, 50% maximum SAR distribution is 5 degree C㎡, occupies the applicator’s geometry area 6.4%. When applicator from 2cm, heats up 3 minutes, 50% maximum SAR distribution area is 4 degree C㎡, occupy the applicator’s geometry area 5.1%. Have a conclusion when applicator is away from phantom model’s surface 1cm,temperature elevates quickly, SAR distribution is uniform.Conclusions1. The microwave thermotherapy combined with radiotherapy and chemotherapy against cervical lymphatic node metastasis from nasopharyngeal carcinoma can effectively enhance the complete response rate, and there were no more serious skin reaction of radiation being found in the group RT+CT+HT.2.Microwave applicator is an important component which launches the microwave energy to the tumor, before carrying on the treatment, to survey the related indicators of microwave applicators should be in advance. The applicator was used in this research, its effective heating area and applicator’s geometry area is not obviously equal, 50%max SAR distribution located at both sides and in the centre of the applicator when heating continually, heat conduction and thermodiffusion rise, the distribution of the highest temperature region seem like“E”.3. Using air coupling, when the applicator is away from phantom model 1cm, in a short time temperatures may achieve 40 degrees above, and the distribution is uniform. because microwave loss in air. Applicator is away from the phantom model 2cm, temperature rise slowly and the thermodiffusion fiercely. So, It may achieve the good goal when applicator heating be away from skin 1cm.4. The applicator in this experiment is most commonly used in domestic, but its specific absorption rate is unsatisfactory. Therefore, the applicator technology still remains to be improved.5. Presently, the factory in domestic does not provide the SAR distribution nearly, the condition of the temperature is unknown. Without survey SAR distribution, the quality of thermotherapy will not be assured, and it will influence clinical curative effect seriously.