Carbon ion therapyComparison of carbon-ion passive and scanning irradiation for pancreatic cancer
Section snippets
Materials and methods
Between November 2013 and February 2014, 13 patients were randomly selected from among patients with inoperable pancreatic cancer who underwent four-field box passive irradiation at our hospital. The characteristics of the enrolled patients are listed in Table 1. The patients were positioned in customized cradles (Moldcare®, Alcare, Tokyo, Japan) and immobilized with a low-temperature thermoplastic shell (Shellfitter®, Kuraray, Osaka, Japan). Treatment planning CT was acquired in
Results
A typical dose distribution and DVH for each plan are shown in Figs 1 and 2, respectively. For the four-field box irradiation, Plan 2 increased OAR dose in the range of <5 Gy (RBE) and decreased dose in the range of ⩾5 Gy (RBE) in comparison to Plan 1. In Fig. 1, cold spots appear in the anterior side of the PTV in Plan 2, because the stomach was cephalad to the PTV; however, it was still at a clinically acceptable level (Plan 1/Plan 2 PTV-D95, 51.6 Gy (RBE)/51.3 Gy (RBE)). For the oblique beam
Discussion
We assessed carbon-ion beam dose planning distributions for pancreatic cancer by comparing passive and scanning irradiation, and four-field box and oblique three-field beam angles. Irrespective of beam angle, scanning irradiation resulted in lower doses to the stomach and duodenum, because scanning irradiation minimizes excessive dose to the normal tissues in front of the target.
The stomach and duodenum received less excessive doses from the passive irradiation in the range of <5 Gy (RBE) (Fig. 2
Conclusions
We found that an oblique three-field scanning irradiation technique was superior to four-field box passive and four-field scanning irradiation. We believe that our results will be helpful for the planning of respiratory-gated scanning irradiation and dose-escalation trials for pancreatic cancer.
Conflict of interest statement
The authors have no conflicts of interest.
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