Deep regional hyperthermia for the whole thoracic region using 8 MHz radiofrequency-capacitive heating device: Relationship between the radiofrequency-output power and the intra-oesophageal temperature and predictive factors for a good heating in 59 patients

Materials and methods: Fifty-nine patients with thoracic cancer treated with radiotherapy plus hyperthermia were retrospectively analysed. The 8-MHz RF capacitive heating device was applied, both the upper and lower electrodes were 300 mm in diameter, placed on opposite sides of the whole thoracic region. All the patients also underwent intra-oesophageal temperature measurements. Results: All thermal parameters, T(min), T(max), T(ave), and %%T >= a parts per thousand yen 41 degrees A degrees C, of the intra-oesophageal temperature highly correlated with the median RF output power (p < 0.0001), and the relations were independent in the multivariable analyses including clinical characteristics (p < 0.01). The performance status showed a statistically significant association on T(max), T(ave) and %%T >= a parts per thousand yen 41 degrees A degrees C (p < 0.05). The patient age and subcutaneous fat at some levels were inversely correlated with the thermal parameters (p < 0.05). Conclusion: The RF output power was significantly correlated with the intra-oesophageal temperature; it could be used as a promising parameter to assess the efficacy of hyperthermia for the whole thoracic region. Higher intra-oesophageal temperature may be achieved in patients with good performance status, younger age and thinner subcutaneous fat.