Prostate cancer recurrence after radical prostatectomy: the role of 3-T diffusion imaging in multi-parametric magnetic resonance imaging.

ABSTRACT

OBJECTIVES: To validate the role of 3-T diffusion-weighted imaging (DWI) in the detection of local prostate cancer recurrence after radical prostatectomy (RP). METHODS: T2-weighted imaging, DWI and dynamic contrast-enhanced MRI (DCE-MRI) were performed with a 3-T magnet in 262 patients after RP. Twenty out of 262 patients evaluated were excluded. MRI results were validated by prostate-specific antigen (PSA) reduction after external beam radiotherapy in group A (126 patients, local recurrence size range 4-8 mm) and by transrectal ultrasound biopsy in group B (116 patients, local recurrence size range 9-15 mm). RESULTS: In group A combined T2-weighted and DCE-MRI (T2+DCE) shows 98 % sensitivity, 94 % specificity and 93 % accuracy in identifying local recurrence; combined T2-weighted and DWI with a b value of 3,000 s/mm(2) (T2+DW3) displays 97 % sensitivity, 95 % specificity and 92 % accuracy, while with a b value of 1,000 s/mm(2) (T2+DW1) affords 93 % sensitivity, 89 % specificity and 88 % accuracy. In group B T2+DCE shows 100 % sensitivity, 97 % specificity and 91 % accuracy in detecting local cancer recurrence; T2+DW3 displays 98 % sensitivity, 96 % specificity and 89 % accuracy; T2+DW1 has 94 % sensitivity, 92 % specificity and 86 % accuracy. CONCLUSION: DCE-MRI is the most reliable technique in detecting local prostate cancer recurrence after RP, though DWI can be proposed as a reliable alternative. KEY POINTS • Diffusion-weighted magnetic resonance imaging (DWI-MRI) is being increasingly used in oncology. • PSA analysis does not distinguish prostate cancer recurrence from distant metastasis. • DWI-MR can diagnose local prostate cancer recurrence after radical prostatectomy. • DWI-MR is almost comparable to DCE-MRI in detecting local recurrence.