ESTRO 2024 - Abstract Book

S1090

Clinical - Gynaecology

ESTRO 2024

Pyrexar Medical Corp., Salt Lake City, UT, USA) integrated into a 1.5T GE Signa Excite scanner. MR thermometry in the target volume was obtained following the proton resonance frequency shift method to derive temperatures from the MR imaging. The MR temperature distributions from hyperthermia were combined with the radiotherapy dose distributions to quantify the therapeutic effect of radiosensitisation by hyperthermia, in terms of EQD2. This calculation was based on an extended version of the Linear-Quadratic (LQ) model, with temperature-dependent parameters α(T) and β(T) (model from van Leeuwen et al, 2018, Int J Hyperthermia [1]).

Results:

For the first-time, hyperthermia treatment target temperatures obtained from MR imaging were used for biological modelling. This was performed for a total number of 39 hyperthermia sessions, with a mean of 3 sessions per patient. A population temperature of 41.1±0.73ºC was achieved on average in the target. Figure 1 shows the enhancement in terms of EQD2 for all 14 patients, displayed by number of hyperthermia sessions. A mean relative improvement in EQD2 of 4.7Gy (range: 1.1-10.3Gy) was obtained during hyperthermia sessions. The EQD2 does not increase linearly with number of sessions, since it is also dependent on achieved temperature during treatment.

Figure 1: Enhancement in EQD2 (Gy) by adding hyperthermia to radiotherapy for patients treated for LACC. Each bar corresponds to a patient.

Conclusion:

This study showed that adding hyperthermia to radiotherapy increases EQD2 and can be a viable option for dose escalation strategies.

Keywords: LACC, dose escalation, hyperthermia

References:

[1] van Leeuwen CM, Oei AL, Ten Cate R, Franken NAP, Bel A, Stalpers LJA, Crezee J, Kok HP. Measurement and analysis of the impact of time-interval, temperature and radiation dose on tumour cell survival and its application in thermoradiotherapy plan evaluation. Int J Hyperthermia. 2018 Feb;34(1):30-38. doi: 10.1080/02656736.2017.1320812. Epub 2017 May 9. PMID: 28540813.