Assessment of serial multi-parametric functional MRI (diffusion-weighted imaging and R2*) with 18F-FDG-PET in patients with head and neck cancer treated with radiation therapy.

Objective: To evaluate the serial changes and correlations between readout-segmented technique with navigated phase correction diffusion-weighted MRI (DWI), R₂*-MRI and 18F-FDG positron emission tomography (PET) CT performed before and during radiation therapy (RT) in patients with mucosal primary head and neck cancer. Methods: The mean apparent diffusion coefficient (ADC_mean) from DWI (at b = 50 and 800 s mm^-2), the mean R₂* values derived from T₂*-MRI, and PET metabolic parameters, including maximum standardized uptake value (SUV_max), metabolic tumour volume (MTV) and total lesional glycolysis (TLG) were measured for the primary tumour. Spearman correlation coefficients were calculated to evaluate correlations between ADC_mean, R₂*, SUV_max, MTV and TLG. A paired t-test was performed to assess the MRI changes and the slope of serial MRI changes during RT. Results: Pre-treatment scans were performed in 28 patients and mid-treatment scans in 20 patients. No significant correlation was found between ADC_mean and either R₂* values or PET parameters. There were significant negative correlations of R₂* values with pre-treatment PET parameters but not with mid-RT PET parameters: pre-SUV_max (p = 0.008), pre-MTV (p = 0.006) and pre-TLG (p = 0.008). A significant rise in ADC_mean was found during the first half (p < 0.001) of RT but not in the second half (p = 0.215) of the treatment. There was an increase of the ADC_mean values of 279.4 [95% confidence interval (95% CI): 210-348] in the first half of the treatment (Weeks 0-3). However, during the second-half period of treatment, the mean ADC value (Weeks 3-6) was 24.0 and the 95% CI (-40 to 88) included zero. This suggests that there was no significant change in ADC values during the second half of the treatment. Conclusion: A significant negative correlation was found between pre-treatment R₂*-MRI and PET parameters. DWI appeared to demonstrate potentially predictable changes during RT. Advances in knowledge: Understanding the correlation and changes that occur with time between potential imaging biomarkers may help us establish the most appropriate biomarkers to consider in future research. [ABSTRACT FROM AUTHOR]