Dose escalation study with respiratory-gated carbon-ion scanning radiotherapy using a simultaneous integrated boost for pancreatic cancer: simulation with four-dimensional computed tomography.
OBJECTIVE
Pancreatic cancer is a difficult to treat disease with a persistently high mortality rate. We evaluated dose distribution simulation with respiratory-gated carbon-ion pencil beam scanning (C-PBS) with a simultaneous integrated boost (SIB) to increase tumour dose, sparing organs at risk (OARs).


METHODS
Using four-dimensional CT data of 12 patients, we delineated gross tumour volume and two clinical target volumes (CTVs). To consider beam range intrafractional uncertainty, we calculated field-specific target volumes, from which two planning target volumes (PTVs) were generated. PTV1 would receive a planned dose of 55.2 Gy [relative biological effectiveness (RBE)-weighted absorbed dose] in 12 fractions, and PTV2 would receive an SIB dose up to 67.2 Gy (RBE). Dose assessments were conducted with regard to the targets and OARs.


RESULTS
CTV2 dose covering 95% of the volume (D95%) increased from 50.3 ± 5.1 Gy (RBE) to 62.5 ± 3.5 Gy (RBE) for a planned dose from 55.2 Gy (RBE) to 67.2 Gy (RBE). For 4 of 12 patients with a distance of ≥5 mm between the tumour and the gastrointestinal tract, CTV2 D95%was ≥95% of planned dose at all dose levels.


CONCLUSIONS
We quantified dose escalation with respiratory-gated C-PBS using SIB for pancreatic cancer and revealed that OAR dose was not affected to the same degree as the tumour dose. Advances in knowledge: A simulation study on respiratory-gated C-PBS with SIB for pancreatic cancer was performed. The results indicated the feasibility of dose escalation for pancreatic cancer, which should be confirmed in clinical trials.
1 Hospital of the National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Chiba, Japan.|2 Department of Radiation Oncology, Faculty of Medicine, Yamagata University, Yamagata, Japan.
Shohei
S
Kawashiro
1 Hospital of the National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Chiba, Japan.
Shinichiro
S
Mori
1 Hospital of the National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Chiba, Japan.
Shigeru
S
Yamada
1 Hospital of the National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Chiba, Japan.
Kentaro
K
Miki
2 Department of Radiation Oncology, Faculty of Medicine, Yamagata University, Yamagata, Japan.
Kenji
K
Nemoto
1 Hospital of the National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Chiba, Japan.
Hiroshi
H
Tsuji
1 Hospital of the National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Chiba, Japan.
Tadashi
T
Kamada
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019583:Dose Fractionation, Radiation; D005260:Female; D056973:Four-Dimensional Computed Tomography / Q000379:methods*; D063193:Heavy Ion Radiotherapy / Q000379:methods*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010190:Pancreatic Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D011879:Radiotherapy Dosage; D016896:Treatment Outcome