Dynamic Changes of 3-Dimensional DW-MRI for Primary Tumor and Cervical Lymph Nodes in Head and Neck Cancer During Radiation Therapy: A Phase 2 Prospective Study

Abstract

Purpose/Objective(s): DW-MRI becomes more and more important, recent study find it help to discriminate the metastatic lymph node and distinguish recurrent tumor. However, we still poorly understand the dynamic changes of it during treatment, especially for 3D-apparent diffusion coefficient (ADC). It is urgent to observe the dynamic changes of 3D-ADC for head and neck cancer during radiotherapy, and to investigate the correlation between the changes of ADC, radiation dose and volume reduction. Materials/Methods: Sixty patients with head and neck cancer treated with image-guided IMRT were enrolled. DW-MRI were performed on 3.0T MRI scanner (b Z 0, 500, 800 s/mm 2 ) at pre-radiation, the 15th, the 25th and post-radiation. Region of interest was the primary tumor (GTV-T) and cervical lymph nodes (GTV-N). The volumes and the maximum, mean and minimum of 3D-ADC value were automatically measured by MIM software. Pearson analysis was used to assess the correlation between 3D-ADC values, delivered radiation dose and tumor volume reduction. Results: All the patients exhibited the mean 3D-ADC increase in GTV-T (0.64AE0.24 x10 -3 mm 2 /s) and GTV-N (0.35AE0.09 x10 -3 mm 2 /s), with the mean increased ratios of 0.50AE0.20 and 0.44AE0.08 between pre-and postradiation. The mean 3D-ADC for GTV-T and GTV-N both changed mostly at the 25 th radiation. However, the changes of the maximum and minimum 3D-ADC values for GTV-T and GTV-N had no correlation with delivered dose and volume reduction. The maximum, mean, and minimum 3D-ADC changes in spinal cord were almost invisible ( 0.04 x10 -3 mm 2 /s). The increased mean ADC had a strong positive correlation with the increased radiation delivered dose for GTV-T and GTV-N respectively (r Z 0.977, P Z 0.023; r Z 0.974, P Z 0.026), and a significantly negative correlation with the volume reduction (r Z -0.989，P Z 0.011; r Z -0.969, P Z 0.031). Conclusion: The mean 3D-ADC value of primary tumor and cervical lymph node can be increased greatly for head and neck cancer during radiotherapy. It had a strong negative correlation with the volume reduction, and a positive correlation with the increased delivered dose. Dynamic 3D-ADC changes during radiotherapy might be an early indicator to assess the treatment response and helps to make treatment strategy for head and neck cancer.