Effect of patient positioning on carbon-ion therapy planned dose distribution to pancreatic tumors and organs at risk

•Dose escalation in pancreatic treatment is often limited by radiosensitivity of OARs.•To improve treatment, we propose patient positioning selection for each beam field.•Positioning selection improves tumor dose, while sparing OARs.•Our method is applicable not only for fixed port treatment but for rotating gantries.•This result provides additional choices to optimize dose distribution.