###### 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. protontherapy; proton; RBE; radiobiology; microdosimetry; Geant4 2021118822. [[https://doi.org/10.3390/app1119882211982119822119822119822119822119822119822119822119822119211982211198221119822111921119822111198221111198221111198221111119822](https://doi.org/10.3390/app1119882211982119822119822119822119822119822119822119822119822119211982211198221119822111921119822111198221111198221111198221111119822)]([https://doi.org/10.3390/app1119882211982119822119822119822119822119822119822119822119822119211982211198221119822111921119822111198221111198221111198221111119822](https://doi.org/10.3390/app1119882211982119822119822119822119822119822119822119822119822119211982211198221119822111921119822111198221111198221111198221111119822))tissues/organs at risk. In fact, its ballistic precision has always been regarded as the main physical pillars of such a treatment modality [1]. However, in recent years, with growing numbers of patients treated and longer follow-up periods, concerns about the potential side effects of protontherapy have arisen [2; 3]. The potential of a given particle irradiation to induce a greater level of specific biological effects compared to photon irradiation, used as a reference, is expressed in terms of its Relative Biological Effectiveness (RBE) [2]. Nowadays, 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. Despite this, data emerging from various radiobiological studies indicate that RBE of protons exceed the accepted value, at least in the distal part of the clinical spread out dose distribution, where high-LET slowing-down protons become predominant. Hence, 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]. Successful treatment planning largely depends on the accuracy of biophysical models. To assure their precision they need to be validated against data from in vitro studies. Therefore, development of the database with experimental results obtained on various cell lines is useful for RBE model validation as well as for comparing different models [11]. While a vast literature exists reporting on the clinical results of eye proton therapy [12; 13; 14; 15; 16], no in vitro data evaluating the cellular radioesponse of uveal cancer cells along a clinical proton SOBP are available.