Abstract
ObjectivesTo evaluate interval changes in heterogeneity on diffusion-weighted apparent diffusion coefficient (ADC) maps and T1-weighted post-gadolinium (T1w post gad) MRI in head and neck carcinoma (HNSCC), with and without chemo-radiotherapy (CRT) response.MethodsThis prospective observational cohort study included 24 participants (20 men, age 62.9 ± 8.8 years) with stage III and IV HNSCC. The primary tumour (n = 23) and largest lymph node (n = 22) dimensions, histogram parameters and grey-level co-occurrence matrix (GLCM) parameters were measured on ADC maps and T1w post gad sequences, performed pretreatment and 6 and 12 weeks post CRT. The 2-year treatment response at primary and nodal sites was recorded. The Wilcoxon signed-rank test was used to compare interval changes in parameters after stratifying for treatment response and failure (p < 0.001 statistical significance).Results23/23 primary tumours and 18/22 nodes responded to CRT at 2 years. Responding HNSCC demonstrated a significant interval change in ADC histogram parameters (kurtosis, coefficient of variation, entropy, energy for primary tumour; kurtosis for nodes) and T1w post gad GLCM (entropy and contrast in the primary tumour and nodes) by 6 weeks post CRT (p < 0.001). Lymph nodes with treatment failure did not demonstrate an interval alteration in heterogeneity parameters.ConclusionsADC maps and T1w post gad MRI demonstrate the evolution of heterogeneity parameters in successfully treated HNSCC by 6 weeks post CRT; however, this is not observed in lymph nodes failing treatment.Advances in KnowledgeEarly reduction in heterogeneity is demonstrated on MRI when HNSCC responds to CRT.
Highlights
Head and neck squamous cell carcinoma (HNSCC) is the seventh most common cancer worldwide [1]
Our study demonstrated that primary tumour ADCmean increased by 6 weeks post CRT
A small sample of non-responding metastatic lymph nodes did not demonstrate such interval evolution of these heterogeneity parameters; standard size criteria were able to predict treatment failure in these patients
Summary
Head and neck squamous cell carcinoma (HNSCC) is the seventh most common cancer worldwide [1]. Whilst earlier detection of residual viable tumour allows for salvage surgery and improved survival [4], it is currently challenging to evaluate this with clinical examination and cross-sectional imaging, due to the presence of posttreatment tissue distortion [5]. Metabolic imaging with 18F-fluorodeoxyglucose positron emission tomography/ computed tomography (18F-FDG PET/CT) [6] may overcome some of the difficulties in interpretation with conventional CT and MRI in this clinical context, but it is generally delayed for at least 12 weeks, due to earlier false positives from post-CRT inflammation [7]. Assessing changes in MRI signal heterogeneity within tumours [8, 9] may better reflect residual disease. We hypothesised that alterations in tumour heterogeneity following CRT would be reflected by diffusionweighted and post-gadolinium T1w MRI and that measurements of signal heterogeneity may augment standard response assessment based on size criteria alone
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