Room: AAPM ePoster Library
Purpose: To investigate the effects of apoptotic cell death due to vascular damage by a single large dose with an improved cellular automata (CA) model.
Methods: The tumor growth process was simulated by considering the amount of oxygen and the density of blood vessels, which supplied oxygen and nutrients required for cell growth. Cancer cells died by the mitotic death process due to radiation, which was quantified by the LQ-model, or the apoptosis due to the lack of nutrients. The radiation caused increased permeation of plasma protein through the blood vessel or the breakdown of the vasculature. Consequently, these changes lead to a change in radiation sensitivity of cancer cells and tumor growth rate after irradiation. The effect of the nutrient-related apoptosis on the tumor control was investigated with a single dose of 6 to25 Gy on day 100. The ratio of the tumor volume at day 200 to day 100 (RV200day/100day) was evaluated by varying the probability of apoptotic cell death, Pnd. Moreover, the temporal change of nutrient concentration in cancer cells after irradiation was evaluated with a single dose of 6, 10, 16, 20 Gy on day 100.
Results: The data of RV200day/100day vs. dose showed a shape similar to the typical cell survival curve. Furthermore, the RV200day/100day values decreased more rapidly with increasing dose as the Pnd increased. The level of the nutrients was lower for larger doses immediately after irradiation, indicating that the higher dose induced larger vascular damage, leading to more apoptotic cell death.
Conclusion: We showed that the apoptosis induced by the lack of nutrients, which in turn caused by the vascular damage by high dose, enhanced the radiation cell kill ability by explicitly modeling the nutrient supply and the damage of blood vessels by radiation in a CA simulation.