Partially Ablative Body Radiotherapy (PABR): A widely applicable planning technique for palliation of locally advanced unresectable tumors

Patients with locally advanced, bulky, and unresectable tumours frequently exhibit frailty and endure symptomatic burden arising from the mass effect of their tumours. Conservative approaches may often fail to provide symptomatic benefit in relatively radioresistant, slower growing tumours such as sarcomas. A novel technique termed Partially Ablative Body Radiotherapy (PABR) administers a highly centralised ablative dose through the utilisation of Simultaneous Integrated Boost (SIB), while delivering low and safe palliative dose to the peripheral regions of tumours. The purpose of this paper is to describe a widely applicable radiation therapy protocol in detail for PABR technique, of which clinical results are available in the previous work7.In summary, PABR prescription of 20Gy in 5 fractions is applied to the PTV and is planned for 95% of the volume to be covered by 95% of the prescribed dose. A dose of 50Gy is planned to the boost target volume, with an allowed maximum dose of up to 65-70Gy, utilising volumetric modulated arc therapy (VMAT). Daily CBCT images are used for delivery verification and imaging study. The centrally located volume exceeding 50Gy effectively achieved the desired outcomes of symptom relief and tumour size reduction. PABR approach is widely accessible and can be readily implemented in a routine clinical setting to address a pressing need for the challenging palliative patient cohort.