Comparison of carbon-ion passive and scanning irradiation for pancreatic cancer

Abstract Purpose To compare carbon-ion beam dose distribution between passive and scanning radiation therapies for locally advanced pancreatic cancer. Materials and methods Thirteen pancreatic cancer patients were included in this study. Four types of treatment planning with respiratory gating were calculated for each patient: a four-field box with passive irradiation (Plan 1), scanning irradiation (Plan 2), a three-field (150°, 180° and 210°) protocol with passive irradiation (Plan 3), and scanning irradiation (Plan 4). The irradiation plans each delivered 55.2 Gy (RBE) to the planning target volume (PTV) and were compared with respect to doses to the PTV and organs at risk (OARs). Results Plan 3 exceeded the dose assessment metrics to the spinal cord. Scanning irradiation plans (Plan 2 and, particularly, Plan 4) offered significantly reduced dosage to the stomach and the duodenum compared with passive irradiation. Conclusion Three-field oblique scanning irradiation for pancreatic cancer has the potential to reduce gastrointestinal exposure and influence of peristalsis on dose distribution.