In Silico Study of Simultaneous Integrated Boost Carbon-Ion Radiotherapy for Locally Advanced Pancreatic Cancer.

Background/aim: Carbon-ion radiotherapy (CiRT) has been used for the treatment of locally advanced pancreatic cancer (LAPC) with uniform dose plan. The aim of the present study is to investigate the effectiveness of a simultaneous integrated boost (SIB) technique with scanned CiRT against LAPC.
Materials and Methods: Data of 21 patients with LAPC were used to compare two treatment planning approaches: a conventional uniform dose approach and a SIB approach. A relative biological effectiveness (RBE)-weighted dose (D _RBE ) of 55.2 Gy (RBE) in 12 fractions was prescribed to the planning target volume (PTV) in the conventional approach. In the SIB approach, D _RBE of 67.2 Gy (RBE) and 43.2 Gy (RBE) in 12 fractions were prescribed to a high-risk PTV (HR-PTV) and low-risk PTV (LR-PTV), respectively. The D _RBE and dose-averaged linear energy transfer (LET _d ) of targets and gastrointestinal tracts as organs at risk (OARs) were evaluated.
Results: The HR-PTV D _90% and LR-PTV D _90% were 64.4±0.6 and 42.5±0.1 Gy (RBE) in SIB approach compared to the PTV D _90% of 54.1±0.4 Gy (RBE) in the conventional approach. All SIB plans achieved the D _2cc lower than 46 Gy (RBE) and V ₃₀ lower than 4 cm ³ within OARs. The SIB approach increased the minimum LET _d within the GTV to 44 keV/μm or higher for 20 out of 21 patients as compared to 16 out of 21 patients in the conventional approach.
Conclusion: The SIB approach effectively increased the RBE-weighted dose and LET _d within the HR-PTV and GTV by accumulating the high-LET stopping carbon-ions into the HR-PTV in addition to the decreased RBE-weighted dose to OARs.
(Copyright © 2024 International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)