ESTRO 2024 - Abstract Book

S1854

Clinical - Mixed sites, palliation

ESTRO 2024

References:

1 Lao Y, Shen D, Zhang W, He R, Jiang M. Immune Checkpoint Inhibitors in Cancer Therapy-How to Overcome Drug Resistance? Cancers (Basel). 2022 Jul 22;14(15):3575. doi: 10.3390/cancers14153575.

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Digital Poster

Shorter irradiation time for palliative care patients treated with VMAT for spinal metastases.

Charlotte D Geurds, Jean-Paul Kleijnen, Mirjam Mast, Laura Bogers, Marieke van Dalum-Mastop, Stefan Hutschemaekers, Lienke Kwakkel-Huizenga, Marc de Goede, Jaap van Egmond, Bianca Borggreven

HMC, Radiotherapie, Leidschedam, Netherlands

Purpose/Objective:

In 2019, there were 119.902 cases of cancer in the Netherlands, about half of these patients have an incurable cancer, often due to metastasis. Roughly two-thirds of terminal cancer patients have bone metastases, with the spine being the most common site. Bone metastases can cause severe pain, which can be treated with radiation therapy in one or two fractions of 8 Gray (Gy). Currently at our department, a VMAT technique with an average irradiation time of four minutes is used. This technique uses the following settings: a single 6 MV 360 degrees arc, a fixed gantry speed and a maximum delivery time (MDT) of 200 seconds (s) in Raystation (version 10B, RaySearch Laboratories). Since many of these patients suffer from pain, we questioned ourselves to what extent do different dose planning VMAT techniques result in a shorter irradiation time. And, if a shorter treatment time can be achieved, what is the effect on the qualitative and quantitative treatment quality compared to the current clinical practice. The aim of this research is to reduce the irradiation time so patients spend less time on the treatment table.

Material/Methods:

For 12 patients with spinal metastasis, clinical treatment plans were anonymized and included in this retrospective study. Reduction of irradiation time was examined, by investigating different planning techniques by modifying optimization settings: maximum delivery time (MDT) setting (180, 140, 100 and 80 seconds); using higher energy (10MV); shorter VMAT arcs (220-140 degrees); variable gantry speed (VGS) or combinations of the latter. This resulted in a total of 228 treatment plans (i.e. 19 planning techniques per patient). Qualitative and quantitative plan parameters were collected to assess the time reduction of these 19 planning techniques and its impact on treatment quality, as well as whether quality standards were met. Based on the results, an optimal planning technique was selected by the radiation oncologist.

Dose distribution quality was measured by the homogeneity index (ideal value between 1 - 1.07) and the conformity index (the higher, the better). Clinical plan quality was assessed evaluating the clinical goals; <2% volume receives