Abstract: PD28-10
Sources of Funding: none

Introduction

Active surveillance (AS) is a viable treatment option for men with low risk prostate cancer. To date no biomarker, including PSA is able to substitute for repeat prostate biopsies to reliably monitor men for disease progression. Multi-parametric MRI has emerged as the imaging modality of choice for localized prostate cancer. We studied the ability of mp-MRI to predict the outcome of repeat biopsy for men with low risk prostate cancer undergoing AS.

Methods

We queried our IRB approved institutional database for men with prostate cancer undergoing mp-MRI. We identified all men with low or low-intermediate risk disease managed initially with AS. All men underwent mp-MRI prior to repeat prostate biopsy. Mp-MRI was analyzed for number and character of lesions by selected radiologists according to prostate imaging reporting and data system (PIRADS) version 2. Trans-rectal US guided prostate biopsies were performed with and without fusion technology depending on presence and size of visible lesions. Men with no or PIRADS 1,2 MRI lesions underwent standard template biopsies with a minimum of 12 cores including anterior zone sampling. Men with visible PIRADS 3-5 lesions underwent lesion directed, targeted biopsies along with template biopsies. Disease re-classification was defined as higher Gleason score on repeat prostate biopsy.

Results

Eighty-six men diagnosed with low risk prostate cancer elected for AS and underwent mp-MRI prior to repeat prostate biopsy. The median interval between MRI and repeat biopsy was 2.6 months. Sixty-seven percent of men (57 of 86) showed at least one PIRADS 4 or 5 lesion. Twenty-seven (31%) of men had disease reclassification on confirmatory biopsy including seven men with Gleason 8 or 9 disease. 18.5% of men with no identifiable or PIRADS 1-3 lesions had grade reclassification compared with 42% of men with PIRADS 4 or 5 lesions. (p=0.03). All grade reclassification in patients with lesions characterized as PIRADS 3 or less was from 3+3 to 3+4. Of the 42% of men with PIRADS 4 or 5 lesions who reclassified on confirmatory biopsy, 7/57 (12%) reclassified to Gleason 8 or 9 on confirmatory biopsy.

Conclusions

Men on active surveillance with no identified or PIRADS ?3 lesions on mp-MRI are still at risk for disease reclassification on repeat biopsy, although no high-risk cancers are missed by MRI. Men with PIRADS 4 or 5 lesions are at higher risk for reclassification including to Gleason 8-10 disease after repeat biopsy.

Funding

none