Direct clinical comparison of ultrasound and radiative electromagnetic hyperthermia applicators in the same tumours

Hyperthermia in conjunction with radiation therapy is a promising method for the treatment of superficially or eccentrically located recurrent or advanced primary malignant tumours. The external hyperthermia applicators most commonly used are radiative electromagnetic (including microwave) or ultrasound devices. Each type of device has its own limitations. The aim was to evaluate the temperature distributions obtained as well as the acute and subacute toxicities in patients that were treated with both radiative radiative electromagnetic and ultrasound applicators to the same tumours. Thirty-nine patients treated to 41 hyperthermia fields for a total of 197 hyperthermia treatments were analysed. Thermal parameter include mean, Tmax, mean Tave, mean Tmin, T50, T90, %T > 43.5 degrees C and %T < 41 degrees C. Acute toxicities including pain in field, referred pain, blister/ulceration, positional discomfort and subacute toxicities (occurring with 24 h of treatment) were determined for each type of hyperthermia applicator. Although there were increased acute toxicities (in-field or referred pain) associated with the ultrasound treatments no significant differences between the two methods of heating were observed in temperature distributions or subacute toxicities. We conclude that there is no generally preferred method of heating superficially or eccentrically located tumours and the type of applicator should be selected on a tumour-size and site-specific basis.