Multiparametric magnetic resonance imaging findings in men with low-risk prostate cancer followed using active surveillance.

UNLABELLED: WHAT'S KNOWN ON THE SUBJECT? AND WHAT DOES THE STUDY ADD?: Up to 35% of men on active surveillance (AS) for clinically localized prostate cancer will experience biopsy reclassification during follow-up. Currently, annual prostate biopsy is recommended in AS programmes. Multiparametric MRI has shown promise in identifying men at risk for immediate reclassification at the time of entry into AS; however, the MRI characteristics of men already enrolled in AS who may be at low risk for disease reclassification have not been fully described. In the present study, we describe the MRI findings of a cohort of men enrolled within AS, with extended follow-up. Among these men, multiparametric MRI demonstrated excellent specificity (0.974) and negative predictive value (0.897) for the detection of pathological index lesions (determined on serial biopsies). These results suggest that men enrolled in AS with a non-suspicious MRI are unlikely to harbour an index cancerous lesion.

OBJECTIVE: To assess the performance of multiparametric magnetic resonance imaging (MRI) in identifying pathological-index (path-index) lesions, defined as cancer present in the same prostate sextant in two separate surveillance biopsies, in men followed within an active surveillance (AS) programme for low-risk prostate cancer (CaP) with extended follow-up.

MATERIALS AND METHODS: A total of 50 men, representing >215 person-years of follow-up in an AS programme, who were referred for prostate MRI were randomly chosen to have their images reviewed by a radiologist with expertise in prostate MRI, who was blinded to biopsy results. Index lesions on MRI were defined as a single suspicious lesion ≥10 mm or >2 lesions in a given prostate sextant. Lesions on MRI were considered suspicious if ≥2 abnormal parameters co-registered anatomically. Path-index lesions were defined as cancer present in a given prostate sextant on two separate biopsy sessions. Sensitivity and specificity were calculated to test the performance of MRI for identifying path-index lesions. Clinical and pathological features were compared between men with and without a MRI-index lesion.

RESULTS: A total of 31 path-index and 13 MRI-index lesions were detected in 22 and 10 patients, respectively. Multiparametric MRI demonstrated excellent specificity and negative predictive value (0.974 and 0.897, respectively) for the detection of path-index lesions. Sensitivity (0.19) and positive predictive value (0.46) were considerably lower. Patients with an index lesion on MRI were younger and less likely to have met the 'Epstein' criteria for very low-risk CaP. Compared with men without an MRI lesion, a significant increase in biopsy reclassification was noted for men with a MRI lesion (40 vs 12.5%, P = 0.04).

CONCLUSIONS: A non-suspicious MRI was highly correlated with a lack of path-index lesions in an AS population. Multiparametric MRI may be useful in both the selection and monitoring of patients undergoing AS.