Session Item

Conventional magnetic resonance imaging (MRI) is used to review tumour morphological changes. Functional MRI measures tumour physiological changes like vascular permeability, cellularity and metabolite concentrations, which occur earlier than morphological changes during treatment. Whether these early physiological changes in nasopharyngeal tumours during treatment can be predictive biomarkers for treatment outcomes are still unknown.

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.

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).

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.