11C-choline PET/CT and whole-body MRI including diffusion-weighted imaging for patients with recurrent prostate cancer

Purpose To compare the detection efficacy of 11C-choline positron emission tomography and computed tomography (PET/CT) with whole-body magnetic resonance imaging (MRI) including diffusion-weighted imaging (DWI) in patients with suspected recurrent prostate cancer. Materials and Methods Fifty-seven patients (mean age 68, range 54-80 years) underwent 11C-choline PET/CT and MRI using T1-weighted (T1w), short-tau inversion recovery (STIR), and DWI. Two readers visually rated suspicious lesions on a 5-point scale in 20 different regions. Clinical follow-up and histopathology served as the standard of reference (SOR). Results Fifty patients (mean PSA 29.9, range 1.0-670 ng/mL) had at least one positive lesion according to the SOR. Twenty-four patients had local recurrence (LR), 27 had lymph node (LN) involvement, and 22 had bone metastases. The overall detection rates for PET/CT and MRI on a patient basis were 94% and 88%, respectively (p = 0.07). The PSA level (>2 ng/mL vs ≤2 ng/mL) significantly influenced the overall performance of PET/CT (p = 0.003) and MRI (p = 0.03). PET/CT was significantly superior to MRI in detecting LR (p = 0.03) and bone metastasis (p = 0.02). We found no difference with respect to the detection of LN metastasis (p = 0.65). Conclusion 11C-choline PET/CT was superior in the detection of local recurrence and bone metastasis on a regional basis. Whole-body MRI including DWI showed similar diagnostic accuracy only for detecting lymph node metastases. Compared with 11C-choline PET/CT, therefore, whole-body MRI including DWI cannot serve as alternative imaging modality for restaging prostate cancer.