Biological dose uniformity in spread-out bragg peak of proton scanning beam therapeutic facility

Introduction. Biological dose uniformity in SOBP of the modem proton therapy facilities is an important issue. The results of a number of studies reveal an increased biological efficiency at the distal area of SOBP. The aim of the study was to verify this effect for Prometeus facility, which provides proton therapy with a scanning pencil beam. Material and methods. The study was conducted at A. Tsyb MRRC. Melanoma B16F10 cells were used for the experiments. The biological efficacy of protons was evaluated by clonogenic assay (cell survival) and comet assay (DNA damage). Proton dose range within the experiments was 4-8 Gy. Cells were irradiated both in monolayer and suspension conditions. Proton biological efficacy along SOBP was evaluated in the proximal, middle and distal positions. All irradiations were carried out with one field. Results of in vitro experiments indicate that Prometeus facility treatment planning system in case of single-field irradiation provides the uniformity of the biological dose in SOBP. According to cell survival, there is a tendency for a slightly greater efficiency of protons in the proximal part of SOBP. Data on DNA damage confirm this conclusion. Conclusion. Therefore, unlike a number of modern installations for proton therapy in the case of the facility used in the study, there is no increase of biological dose in the distal area of SOBP.