ESTRO 2024 - Abstract Book

S2901

Interdiscplinary - Other

ESTRO 2024

Material/Methods:

An extended linear-quadratic model [1] calibrated for the SiHa cell line (cervical cancer) was used to perform Tumor Control Probability (TCP) calculations. A tumor volume of 180 cm3 and a RT schedule consisting of 29 fractions of 2 Gy were assumed for all the simulated patients. For HT, the treatment conditions (number of HT sessions, temperature, time interval) limits were established based on clinically reported data. These conditions were randomly modified to study the TCP dependence on the temperature and the time interval. Finally, four different schedules were used as examples to study the impact of low/high temperature HT sessions (see Figure 2A).

Results:

Under the studied conditions, a baseline TCP (only RT) of 24.8 % was obtained and combining HT with RT significantly increased the TCP: Figure 1A shows that a TCP improvement between 6.9 and 43.7 % was obtained by adding only three low temperature (39 – 40 °C) HT sessions. This TCP improvement increased with the temperature and the total number of HT session. In addition, the radiosensitisation effect decreases with the time interval between HT and RT. However, the speed of this decay (i.e., the influence of the time interval) is still under discussion. Figure 1B presents two simulated scenarios with slow/fast decay of the radiosensitisation effect: Both scenarios showed no clear correlation between the time interval and the outcome. On the other hand, the correlation with the temperature clearly improved when the decay speed was reduced. Therefore, the influence of the time interval can be studied by comparing the treatment outcome with the mean temperature (rather than with the mean time interval). Finally, Figure 2 shows that a low temperature (39 °C) HT session could be compensated with the rest of the HT sessions to obtain a reasonably good outcome. Furthermore, a high temperature (43 °C) HT session only improved the outcome if the other sessions achieved a relatively high temperature. Hence, we can conclude that individual HT sessions usually do not have a significant impact in the outcome.