Radiobiological Outcomes, Microdosimetric Evaluations and Monte Carlo Predictions in Eye Proton Therapy

Giada Petringa,Valentina Bravatà,Giuseppe Antonio Pablo Cirrone,Giorgio Russo,Lorenzo Manti,Pavel Bláha,Vladana Petković,Valeria Conte,Giacomo Cuttone,Aleksandra Ristić Fira,Francesco Paolo Cammarata,Marco Calvaruso,Giusi Irma Forte,Otilija Keta,Ivan Petrović,Selene Richiusa,Luigi Minafra

doi:10.3390/app11198822

Abstract

CATANA (Centro di AdroTerapia ed Applicazioni Nucleari Avanzate) was the first Italian protontherapy facility dedicated to the treatment of ocular neoplastic pathologies. It is in operation at the LNS Laboratories of the Italian Institute for Nuclear Physics (INFN-LNS) and to date, 500 patients have been successfully treated. Even though proton therapy has demonstrated success in clinical settings, there is still a need for more accurate models because they are crucial for the estimation of clinically relevant RBE values. Since RBE can vary depending on several physical and biological parameters, there is a clear need for more experimental data to generate predictions. Establishing a database of cell survival experiments is therefore useful to accurately predict the effects of irradiations on both cancerous and normal tissue. The main aim of this work was to compare RBE values obtained from in-vitro experimental data with predictions made by the LEM II (Local Effect Model), Monte Carlo approaches, and semi-empirical models based on LET experimental measurements. For this purpose, the 92.1 uveal melanoma and ARPE-19 cells derived from normal retinal pigmented epithelium were selected and irradiated in the middle of clinical SOBP of the CATANA proton therapy facility. The remarkable results show the potentiality of using microdosimetric spectrum, Monte Carlo simulations and LEM model to predict not only the RBE but also the survival curves.

Highlights

Proton beam therapy is becoming increasingly available due to its potential to deliver maximal doses on tumour while minimizing irradiation of surrounding healthy tissues/organs at risk
We showed that the LEM-II model, the Monte Carlo-based LEM model and a semi-empirical method based on microdosimetric spectra, can adequately reproduce experimentally derived survival curves from in vitro cell irradiations performed at the mid-SOBP of the CATANA 62 MeV clinical proton beam
Despite the markedly different microdosimetric spectra obtained with these two detectors, when the Loncol’s weighting function is applied to the dose distributions both lead to an assessment of the RBE10 that is in good agreement with radiobiological data for ARPE-19 cells obtained in the same beamline

Summary

Introduction

Proton beam therapy is becoming increasingly available due to its potential to deliver maximal doses on tumour while minimizing irradiation of surrounding healthy tissues/organs at risk. In the proton-therapy clinical practice, a fixed RBE of 1.1 is assumed [3,4,5]. This reflects the known relationship between RBE and Linear Energy Transfer (LET), as in the tumour volume low-LET protons can be generally found. A variable RBE should be used to more precisely describe the radiobiological effects on the tissues and organs involved in the treatment [6,7,8,9,10]

Objectives

Methods

Results

Conclusion