ESTRO 2024 - Abstract Book

S5938

RTT - Treatment planning, OAR and target definitions

ESTRO 2024

Conclusion:

Compared to the treatment with FB, DIBH right breast treatment reduces the doses to the liver and the heart while the dose to the right lung is not statistically different. Interestingly, we saw that the patient immobilization time on the treatment table is not increased significantly by the DIBH technique except for the 1st day of treatment when a CBCT is performed.

Keywords: Deep inspiration breath-hold right breast

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Digital Poster

Comparing palliative treatment plans for vertebral metastases on the RT-SIM CT versus diagnostic CT

Cato Peeters, Jochem Kaas, Martijn Kusters, Paulien Westhoff, René Monshouwer, Marlon van den Broek

Radboudumc, Radiotherapy, Nijmegen, Netherlands

Purpose/Objective:

For patients treated in the palliative setting on vertebral metastases, pain is the most common indication for irradiation of the vertebrae. Currently patients have a CT at the radiotherapy department (RT-SIM CT) in treatment position for treatment planning. In order to reduce the burden of treatment for the patients, it is important to see whether there are options to help the patients as quickly as possible. For this, we investigated whether plans created on an existing diagnostic CT (DCT) resulted in acceptable target coverage during treatment.

Material/Methods:

We included the treatment plans, structure sets and RT-SIM CTs and available DCTs of 20 patients treated between 2019 and 2022, retrospectively. Patients with painful vertebral metastases with recent diagnostic CT imaging and a prescription of 1x8 Gy, 2x8 Gy and 5x4 Gy were eligible for inclusion in this study. Through dynamic planning in Pinnacle, the DCT and the RT-SIM CT were matched and the region of interest (ROI), beams and isocenter of the original plan were transferred to the DCT. After matching, the plan was optimized according to protocol to meet the dose conditions. The plan was then transferred back to the RT-CT, where the dose was recalculated, to measure the difference in dose between the DCT-plan and RT-SIM CT-plan. We looked at the PTV V95%, CTV V95%, Dmax, homogeneity index (HI) and Monitor Units (MU). According to the protocol, the aim is to provide 95% of the prescribed dose to 99% of the PTV. There may be a maximum dose of 110%, as long as it is outside the myelum. The minimum coverage is 95% of the dose to 80% of the PTV, but the clinical aim is to get at least 95%. Furthermore, hotspots should be avoided in the myelum.