Changes in temperatures and thermal doses with fraction number during hyperthermic treatment of locally advanced breast carcinoma

Abstract

Seventeen patients with locally advanced breast cancer were given hyperthermic treatment, and changes in temperatures and thermal doses with fraction number were studied. The changes were related to the vascular density of the treated volume before treatment. Multi-point thermistor probes were used for temperature measurements. Two parameters were determined for each probe location, a steady-state temperature, T_s and a thermal dose, t₄₃. To quantify changes in T_s and t₄₃, linear curves were fitted to plots of these temperature parameters versus fraction number. The slopes of the curves, k_Ts and k_t43, were used to represent the changes in T_s and t₄₃ respectively. Vascular density was determined by histological analysis of biopsies taken from the temperature probe locations before the first heat treatment. Generally, T_s and t₄₃ increased with increasing fraction number. k_Ts and k_t43 were positively correlated to the vascular density of the normal tissue in the treatment volume, i.e. the increase in T_s and t₄₃ was largest in the best-vascularized tissue. The cooling capacity of the normal tissue was probably reduced during the later heat fractions, either because of direct damage to the blood vessels or because of an impaired thermoregulative response. No relationship was found between the temperature parameters and the vascularization of the malignant tissue in the treatment volume. The present results show that the use of a fractionated schedule for heat treatment of locally advanced breast carcinoma may increase the temperatures and thermal doses achieved during treatment. A more uniform heating of the tumours can therefore be achieved by giving multiple heat fractions in the tumour areas that are difficult to heat adequately in one session.

Key Words:

• Breast carcinoma
• fractionated heat treatment
• temperature distribution
• vascular density