Hyperthermia Treatment Planning: Clinical Application and Ongoing Developments

Abstract

Hyperthermia is a proven clinical anti-cancer treatment, used in combination with radiotherapy and/or chemotherapy. During hyperthermia, tumour tissue is heated to 40-43°C using radiofrequency or microwave antennas, which strongly enhances effectiveness of radiotherapy and chemotherapy. Hyperthermia treatment quality depends on tumour temperatures achieved and treatment planning (i.e. simulation and optimization of absorbed power and temperature distributions) could be very useful to ensure and improve treatment quality. Hyperthermia treatment planning was mainly a research tool for decades, because of high computational costs and limited quantitative accuracy of treatment planning predictions due to a lack of patient-specific tissue properties. Thanks to developments over the past decade, treatment planning becomes increasingly important in the clinical workflow. Presently, main clinical applications of hyperthermia treatment planning are 1) applicator selection, 2) heating ability evaluation and 3) on-line treatment guidance. To improve the reliability and further increase applicability of treatment planning, ongoing developments focus on 1) dielectric imaging to derive patient-specific dielectric properties, 2) advanced thermal modelling including discrete vasculature and 3) biological modelling to predict the radiosensitizing effect of hyperthermia in terms of equivalent radiation dose. The increased clinical application and ongoing efforts will further improve treatment quality.

The Effects of Localized Heat on the Hallmarks of Cancer

“…[ 63–65 ] For deep‐lying tumors deemed unsuitable for invasive temperature monitoring, or to provide a greater insight to temperature distribution than sensors can provide alone, treatment planning is now increasingly used in the clinic to provide a simulated thermal map of the target site. [ 62,66,67 ]…”

“…[63][64][65] For deep-lying tumors deemed unsuitable for invasive temperature monitoring, or to provide a greater insight to temperature distribution than sensors can provide alone, treatment planning is now increasingly used in the clinic to provide a simulated thermal map of the target site. [62,66,67] To normalize thermal doses across studies, the benchmark parameter is CEM43, which refers to the cumulative equivalent minutes the tumor is exposed to 43°C. [68][69][70] Moreover, to account for the area of the tumor that is heated, CEM43TX is usedwhere X is a percentage commonly equal to 10, 50, and 90and refers to the duration at which this temperature is exceeded in X% of the measured sites within the tumor.…”

Application of photogrammetry reconstruction for hyperthermia quality control measurements

“…Spatial 3D temperature profiles can be determined using hyperthermia treatment planning (HTP) [10]. HTP represents optimization of treatment parameters such as amplitude and phase of antennas feeding signals in order to maximize deposition of absorbed EM power and/or temperature inside the target region [11,12,13].…”

Treatment planning facilitates clinical decision making for hyperthermia treatments

“…This qualitative reliability allows practical use in clinical decision making, for example in applicator selection to determine a treatment strategy [40][41][42], analyzing the feasibility of heating and predicting possible complications [43,44] and reducing the temperature at hot spot locations [37]. The role of HTP in clinical hyperthermia is emerging and integration into the clinical workflow is becoming common practice [31,36,[44][45][46][47]. Quality assurance guidelines for locoregional hyperthermia have started recommending the use of HTP [25].…”