S576
Clinical – Head & neck
ESTRO 2026
C:29, D:117 and E 343).
Digital Poster 1759
Diffusion-weighted MRI in Boron Neutron Capture Therapy: Early Detection of Treatment Response in Recurrent Head and Neck Carcinoma Venla Loimu 1 , Tiina Seppälä 1 , Kristofer Nyman 2 , Liisa Porra 1 , Lauri Wendland 1 , Mikko Tenhunen 1 , Anu Anttonen 1 1 Comprehensive Cancer Centre, Helsinki University Hospital, Helsinki, Finland. 2 Neuroradiology, Helsinki University Hospital, Helsinki, Finland Purpose/Objective: The aim was to evaluate the apparent diffusion coefficient (ADC) as a biomarker for early detection of treatment response to boron neutron capture therapy (BNCT) in recurrent head and neck carcinoma. ADC has been suggested as a marker for predicting and monitoring early treatment response, like in chemoradiation therapy for head and neck squamous cell carcinoma (HNSCC) [1]. The relationship between ADC and treatment response following BNCT has not been evaluated at different time points yet. Material/Methods: In the ongoing prospective, single-center phase I study patients are receiving two L-boronophenylalanine (BPA)–mediated BNCT treatments administered one month apart using a recently commissioned accelerator-based BNCT facility [2]. In our earlier study, 76% of patients with locally recurrent head and neck carcinoma responded to a comparable two- session BPA-mediated, reactor-based BNCT treatment [3].For n=5 patients diffusion-weighted MRI (DWI) was performed on a 1.5 T GE Artist scanner before BNCT (pre-BNCT), a mean of 27 days (range = 25–31) after the first BNCT (mid-BNCT) in all five patients, and a mean of 29 days (range = 26–31) after the second BNCT (post-BNCT) in four of the patients. DWI was acquired using an echo-planar imaging (EPI) sequence with b-values of 50 and 1000 s/mm ² . Other MRI sequences included T2-weighted, T1-weighted with and without contrast agent. Primary gross tumor volumes (GTVp) were delineated on each MRI scan (pre-, mid-, and post-BNCT), and ADC values were extracted from the GTVps. For data analysis, contrast- enhanced MRI images and corresponding diffusion- weighted (b = 1000 s/mm ² ) and ADC images from each time point (pre-, mid-, and post-BNCT) were registered using MIM software (version 7.3.7). Results: Figure 1 shows median of ADC values at different time points. The values are plotted in descending order of relative ADC increase after first BNCT treatment. The dotted line is pointing the ADC of responding lesions (17%) [4]. After first BNCT, the median of ADC increased 23% and after second BNCT 11%. The pre- BNCT GTVp sizes were median 102 cm3 (A:102, B:88,
Conclusion: The ADC is a promising marker for predicting and monitoring early treatment response in BNCT of recurrent head and neck carcinoma. The relative ADC increase during BNCT is consistent with previous studies for photon radiotherapy even with this heavy pre-treated group of patients. However, more patients need to be treated and followed to get a stronger evidence of ADC as a biomarker. References: 1. Kim S et al. Diffusion-weighted magnetic resonance imaging for predicting and detecting early response to chemoradiation therapy of squamous cell carcinomas the head and neck. Clin Cancer Res 15(3):986- 994,2009.2. Porra L et al. Accelerator-based boron neutron capture therapy facility at the Helsinki University Hospital. Acta Oncol 61(2):269-273,2022.3. Kankaanranta L et al. Boron neutron capture therapy in the treatment of locally recurred head-and-neck cancer: Final analysis of a phase I/II trial. Int J Radiat Oncol Biol Phys 82(1):E67-E75,2012.4. Bartosiak JT et al. Apparent diffusion coefficient (ADC) as an early biomarker for tumor response to radiation therapy, a meta-analysis. Int J Radiat Oncol Biol Phys 114(3):E563,2022. Keywords: BNCT MRI ADC Motor dexterity dysfunction in NPC survivors: association with precentral gyrus dose and cisplatin exposure Gabriel Chun-Hei Wong 1 , Jeffrey Cheuk Fai Lui 1 , Adelina Miu Ching Lau 2 , Ka Man Cheung 1 , Kwok Hung Au 1 , Alexander Yuk Lun Lau 3 , Benny Chung-Ying Zee 4 , James Chung-Hang Chow 1 1 Department of Clinical Oncology, Queen Elizabeth Hospital, Hong Kong, Hong Kong. 2 Department of Clinical Psychology, King’s College Hospital, London, United Kingdom. 3 Division of Neurology, Department of Medicine and Therapeutics, The Chinese University of Hong Kong, Hong Kong, Hong Kong. 4 JC School of Digital Poster Highlight 1761
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