Research on thermal analysis and thermal enhancement effect in loco-regional hyperthermia by means of thermosimulation

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Hyperthermia is an effective modality in cancer treatment especially combined with radiotherapy. However, it is difficult to analyze the relation between thermal parameters and treatment outcome. Thermo-simulation system has been introduced and applied to analyze the thermal factors. Nineteen patients were treated with thermo-radiotherapy using RF capacitive heating system (Thermotron-RF8). Hyperthermia was performed once or twice per week with total 2 to 7 heating sessions and applied with average RF output of 359-1150W and average heating time of 50 minutes. Radiation therapy was given with 2 Gy/fx in 5 fx/week and median dose of 50 Gy. Tb apply thermosimulator, average intensity of RF power supply and heating time were calculated on each patient. Thermal distribution were obtained and displayed every minute on CT images, and thermal factors were analyzed regarding the relation between the local response and relapse free survival time.All thermal factors of patients achieving CR and PR were longer than those in patients achieving NC, but these differences were not significant. The CR and PR rate was 75% in patients in whom EM43T90 was more than 4, and 45% in those where it was less than 4. This rate was 67% in patients in whom teq43T90 was more than 2, and 50% in those where it was less than 2. Median recurrence-free survival time was 5.5 months in patients in whom EM43T90 was more than 4, and 3.6 months in those where it was less than 4. This difference was not significant. In a proportional hazard model, factors that significantly influenced recurrence-free survival time were EM43T90, EM43T50, teq43T90, teq43T50, and histology. After determining thermal factors through a thermo-simulation technique, these factors were demonstrated to have a tendency to influence thermoradiotherapy outcome. Especially, EM43T90 and teq43T90 were the most useful thermal factors to predict treatment outcome.