ESTRO 2024 - Abstract Book

S3534

Physics - Dose prediction, optimisation and applications of photon and electron planning

ESTRO 2024

Validation of a parameterised automated VMAT technique for SIB radiotherapy of head and neck cancer.

Gaia Muti 1,2 , Marco MJ Felisi 2 , Angelo F Monti 2 , Roberto Pellegrini 3 , Chiara Carsana 4 , Mauro Palazzi 4 , Paola E Colombo 2

1 Università di Milano, Fisica, Milano, Italy. 2 ASST GOM Niguarda, Fisica sanitaria, Milano, Italy. 3 Elekta AB, Medical Affairs, Stockholm, Sweden. 4 ASST GOM Niguarda, Radioterapia, Milano, Italy

Purpose/Objective:

Auto-planning systems are gradually entering clinical practice, proving to be a tool for workload reduction while achieving optimized and robust treatment plans. This study investigates the parameterization of a wish-list for the head and neck region for three different simultaneous integrated boost (SIB) prescriptions using mCycle a fully automated lexicographic optimization planning system recently launched under the name of ElektaONE AutoPlanning.

Material/Methods:

Twenty H&N patients are chosen, six are nasopharyngeal cancer (NPC) cases and fourteen are “middle-lower” cancer cases. For each patient three different SIB dose prescriptions are investigated. For each patient and prescription, a manual and auto-plan are calculated. To manage the three prescriptions in the auto-planning an excel template is used. The planning functions of the targets and patient body (external) are linked to the prescription doses of PTV1 and PTV2, thereby changing the prescription fields, the parameters of the constraints are modified. The plans are compared by assessing differences in planning time, dosimetric quality and deliverability. The dosimetric quality is evaluated both qualitatively, with a clinician performing a blinded score evaluation, and quantitatively. The quantitative assessment of the dosimetric quality is carried out by analysing the dosimetric scores for PTV coverage and OARs sparing, and introducing a plan quality index (PQI) for the PTVs and the OARs. For the plan deliverability analysis, the modulation degree, the monitor units, the estimated and the delivered treatment time are investigated. Pre-treatment quality assurance (QA) of twenty manual plans and twenty automatic plans are conducted. Through a signed-rank Wilcoxon test (significance level 0.05) the statistical significance of the analysed parameter is evaluated. The automatic modality significantly reduces the average time from about 2 hours (1:46±0:40, h:min) in manual mode to an average of 11±4 minutes in the automatic mode. In the qualitative and quantitative dosimetric evaluation of the automatic treatment plans, favourable outcomes have been achieved. The radiotherapist deems all plans clinically acceptable, and in many cases (83%), the automatic plan scores equal to or higher than the manual plan. PQI_OARs values are notably higher for the automatic plans in the first and second prescription, indicating the ability to achieve more sparing of the critical organs. This trend doesn’t hold in the third prescription. The requests for PTVs coverage are, on average, well fulfilled in the automatic plans for all three prescriptions, but for the first and third prescription the manual plans show a greater PTVs coverage. However, when considering the overall PQI, the values remain comparable across all prescriptions, as shown in fig. 1. These results suggest that the automatic plans offer greater overall sparing of the OARs at the cost of slightly reducing coverage of the PTVs. Results: