ESTRO 2024 - Abstract Book

S4118

Physics - Inter-fraction motion management and offline adaptive radiotherapy

ESTRO 2024

Comparison of two ART approaches for bladder cancer: “Ethos-ART” vs “Plan of the Day-ART”

Sonia Sapignoli 1 , Paolo Caricato 1 , Alessandro Scaggion 1 , Antonio Giuseppe Amico 1 , Paola Ceroni 1 , Badr El Khouzai 2 , Chiara Paronetto 2 , Matteo Sepulcri 2 , Marco Krengli 2 , Marta Paiusco 1 1 Veneto Institute of Oncology IOV-IRCCS, Medical Physics Department, Padova, Italy. 2 Veneto Institute of Oncology IOV-IRCCS, Radiation Oncology Department, Padova, Italy

Purpose/Objective:

Radiotherapy for bladder cancer is inherently challenging due to the bladder's dynamic volume and shape. This challenge has been successfully addressed through the implementation of Online Adaptive Radiotherapy (oART), which aims to tailor the treatment to the patient's daily anatomy. The approach most commonly implemented relies on selecting the “plan of the day” (POD-ART) from a limited library of treatment plans (Pfull, Pnormal, Pempty). These plans are created “a priori”, to account for expected anatomical changes in bladder volume. Varian’s Ethos™ platform introduced a new strategy for oART based on artificial intelligence for daily anatomical-specific plan re-optimization (Ethos-ART).

This study aimed to investigate and compare these two adaptive approaches through the Ethos™ emulator, a system created to simulate the Ethos™ clinical workflow.

Material/Methods:

This study included five patients previously treated for invasive bladder carcinoma using the POD-ART method. All patients were treated with Volumetric Modulated Arc Therapy (VMAT) plans. Prescription doses and clinical constraints were aligned with the BC2001 trial, specifically 55 Gy delivered in 20 fractions. An isotropic 1.5 cm margin from outer bladder wall to Planning Target Volume (PTV) was used.

For each fraction, we imported in the Ethos™ emulator the clinical delivered plan, chosen from the library of treatment plans (Pfull, Pnormal, Pempty), and the daily CBCT, in order to simulate the POD-ART and the Ethos-ART workflows.

A synthetic CT was created by the system from the daily CBCT. Automated contours were generated by the Ethos Auto-Contouring tool and manual edited by physicians, if required.

Ethos™ generated two plans: the scheduled plan (the clinical POD calculated on the daily anatomy) and the adapted plan (the clinical POD optimized to match the clinical directive on the daily anatomy).

To calculate the POD-ART total delivered dose, the scheduled plan was chosen for each fraction. To calculate the "Ethos-ART" accumulated dose, the best plan between adapted and scheduled plan was chosen by the physician for each fraction.

Comparative assessments were conducted between POD-ART and Ethos-ART accumulated dose, with a specific focus on the fulfillment of clinical goals in the BC2001 trial.

Results: