Introduction: Limited data guide urological practice when employing prostate magnetic resonance imaging (MRI) in active surveillance (AS) protocols. To determine the ability of prostate MRI to predict pathological progression in AS patients, we correlated findings of serial MRI with results of surveillance biopsies.
Methods: Patients on AS with ≥2 prostate MRI and ≥2 prostate biopsies were included. Prostate Imaging-Reporting and Data System (PI-RADS) score upgrade, as assigned by experienced radiologists, was used to assess the ability of imaging to predict pathological biopsy progression. Imaging test statistics and the odds ratio of pathological progression according to MRI upgrade were calculated.
Results: Of 121 patients meeting criteria, 36 (30%) demonstrated MRI upgrade. Biopsy progression was noted in 55 patients (46%). Of these, 20 patients (37%) had biopsy progression predicted by MRI upgrade, while the remaining (n=35) had no lesion upgrade on prostate MRI. Conversely, among those with no biopsy progression (n=66), 16 patients (24%) had a false-positive upgrade on serial MRI. We report a sensitivity and specificity of MRI change for pathological progression of 36% and 76%, respectively. Although MRI change was associated with a positive predictive value of 56% for pathological progression, patients with a high-suspicion lesion (PI-RADS >3) at any time were more likely to experience disease progression, (odds ratio 3.3, 95% confidence interval 1.6-8.0, p<0.01).
Conclusions: Given its modest sensitivity/specificity, serial prostate MRI should be used judiciously as a surveillance tool. However, when prostate MRI demonstrates a PI-RADS >3 lesion, a high index of suspicion should be maintained, as these patients are more likely to progress on AS.