Blood dosimetry during volumetric modulated arc therapy for non-small cell lung cancer: A time-resolved model of circulating particles

Introduction Volumetric modulated arc therapy (VMAT) for non-small cell lung cancer (NSCLC) may result in radiation-induced haematological toxicities. To estimate the dose received by circulating blood particles, we implemented a four-dimensional dose delivery algorithm into a stochastic simulation of blood dynamics. Methods The treatment data of NSCLC patients who received VMAT between 2018 and 2024 were considered. The prescribed dose was 60 Gy/55 Gy/50 Gy delivered in 30/20/25 fractions. To estimate the blood dose, the doses at each control point calculated with the BeamSplitter were used in the Haematological Dose software (HEDOS). The blood dose metrics D98%/mean dose/D2% were calculated and compared with the four-dimensional algorithm (variable dose rates) and the original algorithm (constant dose rates). The main organs contributing to the blood dose were reported. Results The cohort consisted of 115 treatments of 98 patients. As compared with constant dose rates, the population blood D98% decreased (median ΔD98% = −0.1 Gy, p-value < 0.001) with variable dose rates, whilst blood D2% increased (median ΔD2% = 0.1 Gy, p-value < 0.001). The mean blood doses were similar in both calculations (median mean blood dose = 5.4 Gy, p-value = 0.3). At the population level, the largest change in blood D2% was 0.38 Gy. The main organs contributing to the blood dose were lungs (25%), brachiocephalic veins (14%), and aorta (12%). Conclusions VMAT for NSCLC induced a larger blood D2% and a smaller blood D98% as compared with constant delivery.