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Dose-averaged LET escalation with multi-ion therapy for head and neck cancers: a phase I study protocol for a prospective, open-label, single-arm, single-centre trial (MULTI-ION-HN-I)

Ikawa H, Shinoto M, Koto M, Masuda T, Inaniwa T, Takiyama H, Isozaki T, Yamada S et al.

BMJ open, 2025

18 participants · 7 citations

Abstract

Introduction: The standard treatment for unresectable head and neck cancer typically involves radiotherapy (RT) alone or chemoradiotherapy (chemo-RT). Non-squamous cell carcinomas exhibit relatively low radiosensitivity, limiting the efficacy of conventional photon RT. Carbon-ion (C-ion) RT, characterised by high linear energy transfer (LET) and high relative biological effectiveness (RBE), has shown promising outcomes in treating radioresistant head and neck cancers. However, local recurrences still occur, and further improvements in treatment outcomes are needed. To enhance the local control rate, an increase in dose-averaged LET (LETd) to the tumour was considered.Following a simulation study, a clinical trial was conducted to optimise LETd using only C-ion therapy, and its safety was confirmed. However, in this clinical trial, LETd could only be increased to approximately 70 keV/μm. To further escalate LETd, multi-ion therapy using ions heavier than carbon was developed. Simulation studies demonstrated that multi-ion therapy incorporating carbon, oxygen and neon ions could increase LETd up to 90 keV/μm, regardless of tumour size, while maintaining high-dose uniformity within the tumour. Based on these results, a clinical study was planned to evaluate the safety of escalating LETd from 70 keV/μm to 90 keV/μm using multi-ion therapy. The primary objective of this study is to evaluate the safety of escalating LETd to the tumour using multi-ion therapy for head and neck…

How strong is the evidence?

Evidence Hub reads this as a clinical trial, done in people. Its evidence level is 3 of 5 (Moderate · trial / cohort / secondary analysis). Trials without a large randomized design, cohorts and secondary analyses give moderate evidence. Reported size: 18 participants or records.

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