ESTRO 2023

Session Item

Intra-fraction motion management and real-time adaptive radiotherapy

Session Code: 7004

Session Type: Poster (Digital)

Track: Physics

BENEFIT OF DAILY ONLINE CBCT-BASED ADAPTIVE RADIOTHERAPY IN PROSTATE CANCER: A PRELIMINARY ANALYSIS.

Andrea D'Aviero, Italy

Presentation Number: PO-1865

Abstract

Abstract Title:

BENEFIT OF DAILY ONLINE CBCT-BASED ADAPTIVE RADIOTHERAPY IN PROSTATE CANCER: A PRELIMINARY ANALYSIS.

Authors:

Andrea D'Aviero¹, Michele Aquilano¹, Althea Boschetti¹, Francesco Catucci¹, Paolo Gaias¹, Francesca Gruosso^1,2, Martina Iezzi¹, Marco Marras¹, Sebastiano Menna^3,4, Danila Piccari^1,2, Elisa Pilloni³, Domenico Piro^1,4, Francesco Preziosi¹, Flaviovincenzo Quaranta³, Alessia Re¹, Valeria Verusio⁵, Claudio Votta^1,2, Vincenzo Valentini^2,5, Davide Cusumano^3,2, Gian Carlo Mattiucci^1,5

¹Mater Olbia Hospital, Radiation Oncology, Olbia, Italy; ²Fondazione Policlinico Universitario Agostino Gemelli IRCCS, UOC Radioterapia Oncologica, Roma, Italy; ³Mater Olbia Hospital, Medical Physics, Olbia, Italy; ⁴Fondazione Policlinico Universitario Agostino Gemelli IRCCS, UOC Radioterapia Oncologica, Olbia, Italy; ⁵Università Cattolica del Sacro Cuore, Dipartimento di Diagnostica per Immagini, Radioterapia Oncologica ed Ematologia, Roma, Italy

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Purpose or Objective

Aim of this preliminary analysis was to evaluate the potentialities in terms of dosimetric benefit of online daily adaptation in prostate cancer by using a modern CBCT-based linac able to provide online adaptive radiotherapy (online ART) using Artificial Intelligence (AI) system

Material and Methods

A total of 11 prostate cancer patients treated with online ART were enrolled for this study. The patients underwent radiotherapy treatment on an AI-based Linac (Ethos, Varian, US) with a total dose of 67.5 Gy administered in 25 fractions. CTV was defined as prostate and seminal vesicles according to clinical stage. An isotropic margin of 5 mm was added to CTV to obtain PTV except for caudal margin with 0.8 mm expansion.

A daily CBCT was acquired for each treatment session, and a daily online adaptive workflow was performed with the collaboration among a radiation oncologist (RO), a medical physicist and a radiation therapist (RTT).

The AI-system automatically segmented organs at risks (OARs) consisting in rectum, bladder and bowel with an online check by the RO, target volumes (CTV and PTV) were manually delineated.

Treatment plan was automatically reoptimized by the system and two treatment plans were obtained: a predicted plan, consisting in the calculation of the original fluence on the daily anatomy, and an adapted plan, result of a new optimisation.

Dose Volume Histogram for both adapted and predicted plan were obtained daily including clinical target coverage values for PTV (V95% and V105%), also reporting indicators for organs at risk such as bladder (V65Gy), bowel (V45Gy) and rectum (V50Gy).

The difference among predicted and adapted indicators were investigated using the Wilcoxon Mann Whitney test for paired sample. Significance was considered in case of p-value less than 0.05.

Results

A total of 193 fractions were analysed. For predicted plans mean V95% of PTV was 86.4%, while following online adaptation a mean value of 98.4±1.1% was obtained with a statistically significant (p<0.01) difference between the two modalities.

As regards OARs, no significant difference was observed in terms of dose sparing (probably due to the patient preparation procedures), but a reduction in terms of dose variation was found for bladder and rectum when adapted plan was used: the whole data are reported in figure 1.

Conclusion

The results of this preliminary analysis show that performing daily adaptation in prostate leads to a dosimetric benefit with a statistically significant gain in PTV coverage (V95%), with similar risk in terms of toxicity for surrounding OARs, where similar dose values were observed.