ESTRO 2024 - Abstract Book

S5874

RTT - Service evaluation, quality assurance and risk management

ESTRO 2024

delivering cSABR and present an evaluation of the pathway including the need for multi-disciplinary working and impact on service delivery.

Material/Methods:

A partnership with our cardiology colleagues is essential in identifying suitable patients. A UK cSABR MDM occurs monthly to discuss prospective patients and review volumes.

We prospectively measured the time taken to complete each task within the radiotherapy pathway. We collected data on PTV size, number of arcs per plan and beam on time.

Accurate target volume delineation is paramount considering mobility from cardiac-respiratory motion. We designed a respiratory gated contrast-enhanced CT protocol to allow clear delineation of targets and OARs and to minimise the effect of artefacts from metal implants. Patients were scanned with and without abdominal compression. Target delineation was performed jointly by an oncologist and cardiologist. Images and information from previous cardiology investigations were used in conjunction with the planning CT to define the target.

Treatments were planned in Eclipse v15.6 using 6FFF VMAT to conform the 25Gy dose to the target, sparing adjacent healthy tissues. Arc geometry was dependent on target volume.

Patients were treated on a Truebeam STx machine with 6DoF couch using SGRT for patient position monitoring and RPM for motion management. Setup was verified using an optimised CBCT protocol with 3-minute acquisition time. A 4DCBCT was acquired and reviewed online by radiographers and oncologist. A cardiologist and electrophysiologist were present during treatment delivery to oversee any cardiac problems during treatment when the ICD was disabled

Results:

Eight patients have been referred so far, patient eight was not well enough for treatment. Beam on times range from 6 minutes to 11.8, averaging at 8.4 minutes (see table). Lung SABR averages at 2 minutes, this is a significant increase. Patient 6 required discussions with St Louis due to complexities thus increasing the pathway significantly to 112 days.

Time in treatment room (hours)

PTV Volume (cc)

Acute

post

Beam on time (minutes)

Pathway length (days)

PS

at

Arc geometry

Patient Age

Sex

treatment toxicity

MU's

referral

1

69

39.0

F

1

2:00

6.3

3 half arcs 8784

51

Fatigue G1

Fatigue G2 Breathlessness G2 Cough G1

2

69

107.5

M

3

2:00

6

3 half arcs 8465

36