Novel hyperthermia applicator system allows adaptive treatment planning: Preliminary clinical results in tumour-bearing animals

S. Dressel, M.-C. Gosselin, M. H. Capstick, E. Carrasco, M. S. Weyland, S. Scheidegger, E. Neufeld, N. Kuster, S. Bodis, and C. Rohrer Bley, Veterinary and Comparative Oncology, online 11 September, 2017, doi: 10.1111/vco.12340

Hyperthermia (HT) as an adjuvant to radiation therapy (RT) is a multimodality method used to enhance the therapeutic efficacy of the treatment of various tumors. High demands are placed on the hardware and treatment-planning software to guarantee that HT treatments are adequately planned and applied. The aim of this prospective study was to determine the effectiveness and safety of the novel HT system in tumor-bearing dogs and cats in terms of local response and toxicity as well as to compare the predicted response with the data actually achieved during heating. A novel applicator with a flexible number of elements and integrated closed-loop temperature-feedback control system, as well as a tool for patient-specific treatment planning, was used in a combined thermoradiotherapy protocol. There was good agreement between clinical outcomes and predicted outcomes based on planning in 7 of 8 cases. Effective HT treatments were planned and verified with the novel system and provided improved quality of life in all but 1 patient. This individualized treatment planning and controlled heat exposure allows adaptive, flexible, and safe HT treatment of palliatively treated animal patients. As the goal of the study was to test the applicability of the HT hardware and software – tumor response was not considered an endpoint (also due to the limited number of heterogeneous cases) – the findings provide proof-of-principle that effective, homogenous heating can be planned and verified. Future work should focus on image-based systems that allow treatment plans to be replanned and adapted shortly before each session, to take therapy-induced anatomical changes and current physiological conditions into consideration.

The scientific and technical impact of the study can be summarized as:

• A novel HT system – with a patient specific treatment-planning tool and a closed-loop feedback control system to ensure that the applied treatment corresponds to predictions and that provides individually adaptive, flexible, and safe HT treatments – has been developed
• There was good agreement between clinical outcomes and predictions from planning in 7 of 8 cases
• All but 1 animal experienced improved quality of life in a palliative-intent treatment setting
• The study provides proof-of-principle that planned and verified effective, homogenous heating can be used to enhance efficacy of treatment of different tumors

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