High-Linear Energy Transfer Irradiation in Clinical Carbon-Ion Beam With the Linear Energy Transfer Painting Technique for Patients With Head and Neck Cancer

Ryosuke Kohno; Masashi Koto; Hiroaki Ikawa; Sung Hyun Lee; Kana Sato; Mitsuyasu Hashimoto; Taku Inaniwa; Toshiyuki Shirai

doi:10.1016/j.adro.2023.101317

High-Linear Energy Transfer Irradiation in Clinical Carbon-Ion Beam With the Linear Energy Transfer Painting Technique for Patients With Head and Neck Cancer

Adv Radiat Oncol. 2023 Jul 22;9(1):101317. doi: 10.1016/j.adro.2023.101317. eCollection 2024 Jan.

Authors

Ryosuke Kohno^{1

2}, Masashi Koto³, Hiroaki Ikawa³, Sung Hyun Lee⁴, Kana Sato⁵, Mitsuyasu Hashimoto², Taku Inaniwa¹, Toshiyuki Shirai¹

Affiliations

¹ Department of Accelerator and Medical Physics, Institute for Quantum Medical Science, National Institute for Quantum Science and Technology, Chiba, Japan.
² Department of Radiologic Sciences, Graduate School of Health and Welfare Sciences, International University of Health and Welfare Graduate School, Tokyo, Japan.
³ QST Hospital, National Institute for Quantum Science and Technology, Chiba, Japan.
⁴ Department of Heavy Particle Medical Science, Graduate School of Medical Science, Yamagata University, Yamagata, Japan.
⁵ Department of Radiology, IUHW Narita Hospital, Chiba, Japan.

Abstract

Purpose: Dose-averaged linear energy transfer (LET_d) is one of the important factors in determining clinical outcomes for carbon-ion radiation therapy. Innovative LET painting (LP) has been developed as an advanced form of conventional intensity modulated carbon-ion radiation therapy (IMIT) at the QST Hospital. The study had 2 motivations: to increase the minimum LET_d (LET_dmin) and to improve uniformity of the LET_d distribution within the gross tumor volume (GTV) by using LP treatment plans for patients with head and neck cancer while maintaining the relative biologic effectiveness (RBE)-weighted dose coverage within the planning tumor volume (PTV) the same as in the conventional IMIT plan.

Methods and materials: The LP treatment plans were designed with the in-house treatment planning system. For the plans, LET_d constraints and LET_dmin, goal-LET_d, and maximum-LET_d (LET_dmax) constraints for the GTV were added to the conventional dose constraints in the IMIT prescription. For 13 patients with head and neck cancer, the RBE-weighted dose to 90% (D90) and 50% (D50) of the PTV and the LET_dmin, mean (LET_dmean), and LET_dmax values within the GTV in the LP plans were evaluated by comparing them with those in the conventional IMIT plans.

Results: The LP for 13 patients with head and neck cancer could keep D90s and D50s for the PTV within 1.0% of those by the conventional IMIT. Among the 13 patients, the mean LET_dmin of the LP plans for the GTV was 59.2 ± 7.9 keV/μm, whereas that of the IMIT plans was 45.9 ± 6.0 keV/μm. The LP increased the LET_dmin to 8 to 24 keV/μm for the GTV compared with IMIT.

Conclusions: While maintaining the dose coverage to the PTV as comparable to that for IMIT, the LP increased the mean LET_dmin to 13.2 keV/μm for the GTV. For a GTV up to 170 cm³, LET_d > 44 keV/μm could be achieved using LP, which according to previous studies was associated with lower recurrence. In addition, the LP method delivered more uniform LET_d distributions compared with IMIT.