Prognostic value of MR visibility/invisibility in men on Active Surveillance.

Objective: We sought to determine, in a prospective long term cohort, the prognostic value of negative MR imaging with respect to upgrading and need for intervention in men on AS.

Method: A long term prospective single centre study of men on Active surveillance with MR imaging. Primary outcome was upgrading on biopsy and rate of intervention. After incorporation of MRI into the AS protocol in 2013, men with negative imaging underwent systematic biopsy only for cause.

Results: Five hundred and thirty AS patients had one or more MRI, with median follow-up of 8.5 years. At baseline, 39 patients (7.4%) had negative MRIs 161 (30%) equivocal, and 330 (62%) had a positive MRI. Two hundred and twenty-nine patients were upgraded; 5% with invisible lesions, 34% with PiRADS 3, and 52% with PiRADS 4-5. Two hundred and twenty-nine (43%) of the 530 men were eventually treated. No patient with a negative PiRADS was treated, vs 36% with PiRADS 3 and 52% with PiRADS 4-5 (p < 0.001). In 331 men with serial MRIs, upgrading occurred in 46% of men with stable or improved MRI, and 57% in those with MRI progression. In the 70 patients whose MRI improved from PiRADS 4-5 to 3, 46% were upgraded. No patients who transitioned from PiRADS 3-5 to 1-2 were upgraded. Time to grade progression was highly inversely correlated with PIRADS score.

Conclusion: MRI invisible cancers demonstrated dramatically reduced rates of progression and no patient required intervention. Despite the absence of routine biopsies in the MR negative group, none of these patients progressed over time to GG ≥ 3 or metastatic disease. This suggests that, in men on active surveillance, image guided management, restricting biopsies to targeted biopsies of regions of interest, is sufficient to identify clinically significant cancers.