Restricted water diffusibility as measured by diffusion-weighted MR imaging and choline uptake in ¹¹C-choline PET/CT are correlated in pelvic lymph nodes in patients with prostate cancer

Purpose: ¹¹C-Choline-positron emission tomography (PET)/computed tomography (CT) is increasingly used in patients with prostate cancer. Another promising technique for assessment of tumor biology is diffusion-weighted MR imaging (DWI). The aim of the study was to compare the functional parameters standardized uptake value (SUV) in PET and apparent diffusion coefficient (ADC) value in DWI of lymph nodes in prostate cancer patients. Procedures: Fourteen patientswith prostate cancer underwent DWI at 1.5T and ¹¹C-Choline- PET/CT. ADC values and SUVs of all lymph nodes larger than 5 mm (n=55) were compared by using linear regression analysis. Performance of DWI and ¹¹C-Choline PET was assessed by receiver operator characteristic curve analysis using histopathology or clinical follow-up as standard of reference. Results: ADC values and SUV showed a moderate but highly significant inverse correlation (r=-0.5144, p<0.0001). In lymph nodes with low ADC values, the dispersion of SUV was more pronounced.Moreover, a highly significant difference was observed for mean ADC values and SUV in lymph nodes considered as benign or malignant by follow-up/histopathology (ADC 1.60±0.24 vs. 1.09±0.23×10 ^-3 mm ²/s; SUV 1.82±0.57 vs. 4.68±03.12; p<0.0001, respectively). Conclusion: These pilot data propose the ADC value in DWI as a new potential imaging biomarker which might provide additional information on tumor pathophysiology compared to the SUV in ¹¹C-Choline PET/CT.