Adaptive planning based on single beam optimization in passive scattering carbon ion radiotherapy for patients with pancreatic cancer

Radiation Oncology

Toshiaki Matsui¹  Yang Li²  Yoshiki Kubota³  Takashi Nakano³  Shintaro Shiba³  Tatsuya Ohno³  Mutsumi Tashiro³  Shohei Okazaki³  Masahiko Okamoto³ 

[1] Graduate School of Medicine, Gunma University, Maebashi, Japan;Graduate School of Medicine, Gunma University, Maebashi, Japan;Department of Radiation Oncology, Harbin Medical University Cancer Hospital, Harbin, China;Gunma University Heavy Ion Medical Center, Maebashi, Japan;

关键词: Carbon-ion radiotherapy;    Adaptive planning;    Pancreatic cancer;    Accumulated dose assessment;    Robustness of treatment;   

DOI  :  10.1186/s13014-021-01841-2

来源: Springer

【 摘 要 】

BackgroundDaily anatomical deviations may distort the dose distribution in carbon ion radiotherapy (CIRT), which may cause treatment failure. Therefore, this study aimed to perform re-planning to maintain the dose coverage in patients with pancreatic cancer with passive scattering CIRT.MethodsEight patients with pancreatic cancer and 95 daily computed tomography (CT) sets were examined. Two types of adaptive plans based on new range compensators (RCs) (AP-1) and initial RCs (AP-2) were generated. In AP-2, each beam was optimized by manually adjusting the range shifter thickness and spread-out Bragg peak size to make dose reduction by < 3% of the original plan. Doses of the original plan with bone matching (BM) and tumor matching (TM) were examined for comparison. We calculated the accumulated dose using the contour and intensity-based deformable image registration algorithm. The dosimetric differences in respect to the original plan were compared between methods.ResultsUsing TM and BM, mean ± standard deviations of daily CTV V95 (%) difference from the original plan was − 5.1 ± 6.2 and − 8.8 ± 8.8, respectively, but 1.2 ± 3.4 in AP-1 and − 0.5 ± 2.1 in AP-2 (P < 0.001). AP-1 and AP-2 enabled to maintain a satisfactory accumulated dose in all patients. The dose difference was 1.2 ± 2.8, − 2,1 ± 1.7, − 7.1 ± 5.2, and − 16.5 ± 15.0 for AP-1, AP-2, TM, and BM, respectively. However, AP-2 caused a dose increase in the duodenum, especially in the left–right beam.ConclusionsThe possible dose deterioration should be considered when performing the BM, even TM. Re-planning based on single beam optimization in passive scattering CIRT seems an effective and safe method of ensuring the treatment robustness in pancreatic cancer. Further study is necessary to spare healthy tissues, especially the duodenum.

【 授权许可】

CC BY