ESTRO 2022 - Abstract Book

S129

Abstract book

ESTRO 2022

Materials and Methods Nineteen patients with nasopharyngeal carcinoma (NPC) who have received concurrent chemo-radiation therapy in 7 weeks were recruited for prospective longitudinal monitoring by weekly functional MRI scans. Dynamic contrast-enhanced (DCE) MRI, diffusion-weighted (DW) MRI and MR spectroscopy (MRS) were scanned before treatment, weekly during treatment and post-treatment. Three patients whose post-treatment nasopharyngeal tumour volume shrinkages less than 50% are classified as poor responders to the treatments, while the rest are classified as responders. Tumour vascular permeability parameters, water diffusivity characteristics and metabolite concentrations were studied with DCE-MRI, DW-MRI and MRS respectively at different time points for any significant difference between responders and poor responders to the treatments. Vascular permeability parameters were measured by DCE-MRI following Tofts compartment model between the blood plasma and the extra-vascular extra-cellular space (EES). They include volume transfer constant from blood plasma to EES (K trans ), rate constant from EES to blood plasma (K ep ), volume of EES per unit volume of tissue (V e ) and initial area under curve for 60s of contrast arrival (iAUC60) in the time-intensity curve. Water diffusivity characteristics were measure by DW-MRI with apparent diffusion coefficient (ADC) values. Metabolite concentrations were measured by the corresponding peaks on MRS spectrum. Results Our results show that in DCE-MRI, the mean increases in V e from the first week to the third week of treatment are significantly different between responders (41.9%, SD 27.2%) and poor-responders (5.6%, SD 17.7%) (p=0.039). In DW-MRI, the mean increases in ADC from pre-treatment to the third week of treatment are marginally significant between responders (41.8%, SD 28.0%) and poor-responders (16.0%, SD 5.9%) (p=0.07). Conclusion Our results demonstrate that early changes in tumour vascular permeability and diffusivity in NPC during the concurrent chemo-radiation therapy are associated with post-treatment tumour shrinkage, which serves important prognostic values in predicting tumour shrinkage at the early phase of treatment. We anticipate our study to be a starting point for investigating the applications of functional MRI scans as the prognostic tools for early prediction and therapeutic monitoring for NPC patients with a larger cohort. M. Dubec 1,2 , R.A. Little 1 , D.L. Buckley 2,3 , C. Hague 4 , J. Price 4 , M. Berks 1 , S. Cheung 1 , A. Salah 5 , D. Higgins 6 , J.H. Naish 7,9 , J.C. Matthews 8 , M. van Herk 1 , G.J. Parker 10,11 , A. McPartlin 4 , J.P. O'Connor 1,12,13 1 University of Manchester, Division of Cancer Sciences, Manchester, United Kingdom; 2 The Christie NHS Foundation Trust, Christie Medical Physics and Engineering, Manchester, United Kingdom; 3 Biomedical Imaging, University of Leeds, Leeds, United Kingdom; 4 The Christie NHS Foundation Trust, Clinical Oncology, Manchester, United Kingdom; 5 The Christie NHS Foundation Trust, Proton Beam Therapy, Manchester, United Kingdom; 6 Philips UK&I, MR Clinical Science, Farnborough, United Kingdom; 7 Manchester University NHS Foundation Trust, MCMR, Manchester, United Kingdom; 8 University of Manchester, Neuroscience and Experimental Psychology, Manchester, United Kingdom; 9 Bioxydyn Ltd, Bioxydyn, Manchester, United Kingdom; 10 University College London, Centre for Medical Image Computing, London, United Kingdom; 11 Bioxydyn Ltd, Bioxydyn, London, United Kingdom; 12 The Christie NHS Foundation Trust, Radiology, Manchester, United Kingdom; 13 Institute of Cancer Research, Radiotherapy and Imaging, London, United Kingdom Purpose or Objective Hypoxia promotes tumour development, progression and treatment resistance. Oxygen-enhanced (OE)-MRI has shown promise as a non-invasive method of mapping and quantifying hypoxia; the oxygen-induced change in longitudinal relaxation rate ( Δ R 1 ) can identify normoxic tumour and distinguish this from hypoxic tumour, which has no demonstrable oxygen- induced change in Δ R 1 . This technique has previously detected hypoxia modification in patients with non-small cell lung cancer (Salem 2019 CCR). We hypothesised that Δ R 1 could be developed in head and neck (H&N) squamous cell carcinoma. Materials and Methods Participants were recruited after written informed consent to an ethics approved study. Imaging was performed on a 1.5 T Philips Ingenia MR-RT system. Sequences were optimised in 4 healthy volunteers and included anatomical imaging, quantitative T 1 measurement (3D inversion recovery turbo field echo, inversion times (TI) = 100, 500, 800, 1100, 4300 ms) and a dynamic OE acquisition using the same sequence as for T 1 measurement with TI = 1100 ms, temporal resolution = 12 s. Gas delivery during dynamic series: scans 1-25 (medical air; 21% O 2 ), 26-70 (100% O 2 ) and 71-91 (medical air; 21% O 2 ). A gas blender ensured a flow rate of 15 l/min via a high concentration mask. A finalised protocol was run in a further 6 healthy volunteers, each imaged twice (8 ± 3 days apart), and in 4 patients with H&N carcinoma, imaged 1 or 2 times at baseline and then once during chemoradiotherapy (CTRT). Analysis used MATLAB (Mathworks). Quantitative T 1 maps enabled conversion of signal change to Δ R 1 (where Δ R 1 = R 1,O2 – R 1,air ). In volunteers, regions of interest were positioned in three tissue regions; the nasal concha (NC), tongue and brain. Mean Δ R 1 values and within-subject coefficient of variation (wCV) were obtained for each tissue. Patient tumour volumes were delineated on T 1 weighted post gadolinium contrast images. Δ R 1 was measured for each tumour and tissue volume at each visit. Results Volunteer Δ R 1 curves for the two visits for the NC, tongue and brain regions are shown in Figure 1. Mean Δ R 1,NC = 0.059 ± 0.027 s -1 (p < 0.001, Δ R 1 change); Δ R 1,Tongue = 0.001 ± 0.012 s -1 (p = 0.86); Δ R 1,Brain = 0.005 ± 0.005 s -1 (p = 0.04) (Figure 1a-c), PD-0155 Optimising oxygen-enhanced MRI for patients with head and neck carcinoma