Feasibility of on-line temperature-based hyperthermia treatment planning to improve tumour temperatures during locoregional hyperthermia

Background: The effectiveness of hyperthermia is strongly dependent on the achieved tumour temperatures. Phased-array systems allow flexible power steering to realise good tumour heating while avoiding excessive heating in normal tissue, but the limited quantitative accuracy of pre-treatment planning complicates realising optimal tumour heating. On-line hyperthermia treatment planning could help to improve the heating quality. This paper demonstrates the feasibility of using on-line temperature-based treatment planning to improve the heating quality during hyperthermia in three patients.

Methods: Hyperthermia treatment planning was performed using the Plan2Heat software package combined with a dedicated graphical user interface for on-line application. Electric fields were pre-calculated to allow instant update and visualisation of the predicted temperature distribution for user-selected phase-amplitude settings during treatment. On-line treatment planning using manual variation of system settings for the AMC-8 hyperthermia system was applied in one patient with a deep-seated pelvic melanoma metastasis and two cervical cancer patients. For a clinically relevant improvement the increase in average target temperature should be at least 0.2?°C.

Results: With the assistance of on-line treatment planning a substantial improvement in tumour temperatures was realised for all three patients. In the melanoma patient, the average measured target temperature increased from 38.30?°C to 39.15?°C (i.e.?+0.85?°C). In the cervical cancer patients, the average measured target temperature increased from 41.30?°C to 42.05?°C (i.e.?+0.75?°C) and from 41.70?°C to 42.80?°C (i.e.?+1.1?°C), respectively.

Conclusion: On-line temperature-based treatment planning is clinically feasible to improve tumour temperatures. A next, worthwhile step is automatic optimisation for a larger number of patients.