ESTRO 2024 - Abstract Book

S1918

Clinical - Mixed sites, palliation

ESTRO 2024

to enable the delivery of stereotactic body radiotherapy (SBRT) to cardiac targets 3 . We report our initial experience of the efficacy and safety of cardiac MRgRT.

Material/Methods:

We prospectively collected data of three patients (2 intracardiac and 1 pericardial) from our registry 4 who underwent cardiac MRgRT on the Elekta Unity across two institutions between April 2021 and June 2023. Patients were simulated using 4DCT in supine position with arms down in a custom vacbag and free breathing with a compression belt. The prescribed dose was 35-40 Gy in 5 fractions on non-consecutive days using the Adapt to Shape workflow. The 3D vane sequence, which provides images with reduced motion artefacts, was used for target delineation for 2 patients, and the T1 sequence was used for 1 patient. A uniform 3-7 mm PTV margin was used depending on target motion on 4DCT. The treatment was monitored using a balanced T1-/T2-weighted 2D cine MRI. Response rates were determined based on pre and post-MRgRT PET/CT.

Results:

Patient demographic and treatment details are summarized below in table 1. Our mean follow-up time was 6 months (range 4-9 months). None of the patients were symptomatic at presentation. All three patients achieved a good partial response to MRgRT at the most recent follow up. Treatment was well tolerated, with no reported treatment-related toxicities > Grade 1 as per the CTCAE version 5.0 criteria 4 .

Table 1.

ECOG status

Patient

Age

Gender

Histology

Location

Prescription GTV (cc)

PTV (cc)

A

79

F

1

Sarcoma

Left atrium 35Gy/5#

GTV3500=15.1

PTV3500=55.7

Metastatic melanoma Metastatic poorly

Posterior pericardium

B

81

M

1

40Gy/5#

GTV4000=6.7 PTV4000=31.7

Interatrial septum

C

70

M

1

differentiated sarcomatoid carcinoma

40Gy/5#

GTV4000=10.0 PTV4000=36.7

Conclusion:

Our study supports that MRgRT on the Elekta Unity is a promising, safe, and efficacious treatment platform to deliver SBRT to patients with cardiac targets. Patient-reported outcomes and long term follow up data are being collected on our registry for further assessment.

Keywords: cardiac tumours, MR-guidance, SBRT

References: