Influence of dose-averaged linear energy transfer on tumour control after carbon-ion radiation therapy for pancreatic cancer

• Published in: Clinical and translational radiation oncology Vol. 21; pp. 19 - 24
• Main Authors: Hagiwara, Yasuhito, Bhattacharyya, Tapesh, Matsufuji, Naruhiro, Isozaki, Yuka, Takiyama, Hirotoshi, Nemoto, Kenji, Tsuji, Hiroshi, Yamada, Shigeru
• Format: Journal Article
• Language: English
• Published: Ireland Elsevier B.V 01.03.2020; Elsevier
• Subjects: Carbon ion radiotherapy; Linear energy transfer; Pancreatic cancer; Linear energy transfer; Pancreatic cancer; Carbon ion radiotherapy
• ISSN: 2405-6308; 2405-6308
• DOI: 10.1016/j.ctro.2019.11.002

•High LET and high RBE of carbon ion made it a promising tool for treating pancreatic cancers.•Dose averaged LET minimum within the GTV is significantly associated with local control.•Outcome of CIRT in pancreatic cancers can be improved by modulating dose averaged LET within the GTV. High linear energy transfer (LET) radiation carbon-ion radiotherapy (C-ion RT) is one of the most promising modalities for treating unresectable primary pancreatic cancers. However, how LET contributes to a therapeutic effect is not clear. To assess whether there is an enhanced effect of high LET radiation on tumour control, we aimed to determine the impact of dose-averaged LET on local control (LC) of primary pancreatic tumours. A retrospective analysis of 18 patients with primary pancreatic carcinomas treated with definitive C-ion RT with concurrent chemotherapy in 2013 was conducted. The dose of irradiation was 55.2 Gy (RBE). The relationship between dose-averaged LET and LC of primary tumours was evaluated. All patients had histologically confirmed adenocarcinoma. The median follow-up duration was 22 months. The actuarial LC and overall survival (OS) at 18 months were 62.5% and 70.1%, respectively. There were no cases of grade ≥3 late toxicities observed. Local recurrences developed in four patients (22%), all of which were infield central recurrences. Although there were no significant differences in gross tumour volume (GTV) dose coverage, patients with higher minimum dose-averaged LET (LETmin) values within the GTV had better LC (dose-averaged LETmin ≥44 keV/microm; 18-months LC 100.0% vs 34.3%; p = 0.0366). Dose-averaged LETmin within the GTV was significantly associated with LC of primary pancreatic cancers. Our data suggest that outcomes for patients with unresectable primary pancreatic cancers receiving C-ion RT can be improved by modulating the dose-averaged LET within the GTV.