ESTRO 2024 - Abstract Book

S5962

RTT - Treatment planning, OAR and target definitions

ESTRO 2024

Purpose/Objective:

The objective of this work was to establish how radiographer-led planning pathways may support the anticipated increased uptake of 5# prostate SABR in the United Kingdom. The work sought to answer the following:

• Can radiographer-led contouring of clinical target volumes (CTVs) be used to increase access and efficiency for 5# prostate SABR in the United Kingdom? • Can radiographer CTVs be deemed clinically acceptable for delivery of 5# prostate radiotherapy according to PACE criteria? • What degree of inter-observer variability exists between radiographers completing prostate and seminal vesicle CTVs?

Material/Methods:

Two stereotactic specialist radiographers independently contoured 14 cases previously treated with 5# in their institution, a private provider within the United Kingdom spanning geographically disparate sites. The 14 cases were originally contoured by 7 different clinical oncologists across 6 centres. Radiographers and doctors followed PACE guidelines using planning CT and MRI; CTVs were created according to PACE/NCCN risk guidelines. All patients had fiducial markers and rectal spacers. All contouring was completed in MIM Maestro (MIM Software). Absolute volumes, DICE coefficients and mean distance to agreement were calculated in MIM Maestro for CTVp, CTVpsv and CTVsv (if applicable) for each radiographer versus the original clinical oncologist contours. The radiographers’ contours were compared against each other to determine inter-observer variability when following a set protocol.

Time taken for radiographers to complete the contouring was recorded and combined with overall planning time for the original plans to gauge “time in planning” for these cases on a radiographer-led pathway.

Two radiographer-contoured cases were replanned using standard margins to determine whether clinically acceptable plans could be produced that achieved tolerances. The dosimetry was compared with the original doctor volumes to assess the coverage of the original targets.

Results:

The mean time taken by Radiographer 1 to complete CTV contouring per case was 7.7 minutes, and 10.2 minutes for Radiographer 2. For all cases, mean overall time in planning (originally, across the planning workforce) including organ at risk delineation, CTV voluming by radiographers and plan optimisation, was 9 hours 20 minutes, with the fastest time being 3.5 hours; majority falling between 5.6 and 15.7 hours (Fig 1).