Active Surveillance of Prostate Cancer: Use, Outcomes, Imaging, and Diagnostic Tools

Abstract

Active surveillance (AS) has emerged as a standard management option for men with very low-risk and low-risk prostate cancer, and contemporary data indicate that use of AS is increasing in the United States and abroad. In the favorable-risk population, reports from multiple prospective cohorts indicate a less than 1% likelihood of metastatic disease and prostate cancer-specific mortality over intermediate-term follow-up (median 5-6 years). Higher-risk men participating in AS appear to be at increased risk of adverse outcomes, but these populations have not been adequately studied to this point. Although monitoring on AS largely relies on serial prostate biopsy, a procedure associated with considerable morbidity, there is a need for improved diagnostic tools for patient selection and monitoring. Revisions from the 2014 International Society of Urologic Pathology consensus conference have yielded a more intuitive reporting system and detailed reporting of low-intermediate grade tumors, which should facilitate the practice of AS. Meanwhile, emerging modalities such as multiparametric magnetic resonance imaging and tissue-based molecular testing have shown prognostic value in some populations. At this time, however, these instruments have not been sufficiently studied to consider their routine, standardized use in the AS setting. Future studies should seek to identify those platforms most informative in the AS population and propose a strategy by which promising diagnostic tools can be safely and efficiently incorporated into clinical practice.

Figure 1

A 71 year man with serum PSA of 5.47ng/ml was found to have Gleason score 3+3 cancer (5%) on random biopsy. Due to rising PSA levels, he underwent MRI scan prior to enrollment in active surveillance. (A). An axial T2-weighted MRI scan shows a PI-RADS 5 lesion in the left mid-anterior transition zone (arrow). (B-D) The lesion is positive on the apparent diffusion coefficient map (B), diffusion-weighted MRI (b=2000mm/s²) (C), and dynamic contrast-enhanced MRI (D; arrows). A TRUS/MRI fusion-guided candidate after multiparametric MRI and a TRUS/MRI fusion-guided biopsy approach. Abbreviations: PI-RADS, Prostate Imaging Reporting and Data System; PSA, prostate-specific antigen; TRUS, transrectal ultrasonography.

Figure 2

A comparison of pathology-defined candidates (top row) for active treatment (yellow) and active surveillance (orange) versus definitions based on multiparametric MRI, the Epstein criteria, the D’Amico criteria, and CAPRA score. Each patient is represented by a column of the array. Note that multiparametric MRI results most closely mirrored pathology results with fewest “false-positive” decisions for active treatment in good active surveillance candidates. Abbreviations: CAPRA, Cancer of the Prostate Risk Assessment; MP, multiparametric. Reprinted from Turkbey et al55 with permission from the publisher.

Figure 3

A 59-year-old man presenting with a serum PSA of 4.68 ng/ml. (A–C) An axial T2-weighted MRI scan (A), apparent diffusion coefficient map (B), and b1500 diffusion-weighted MRI (C) show a lesion in the left mid-peripheral zone (arrows). This lesion was biopsied and found to harbor Gleason 3 + 3 prostate cancer (10%). The patient elected active surveillance. (D–F) A 1-year follow-up MRI scan (serum PSA = 5.10 ng/ml) shows that the lesion is stable in size and MRI signal features. The follow-up biopsy also revealed Gleason 3 + 3 prostate cancer (15%). MRI may become a tool for monitoring patients on active surveillance. Abbreviation: PSA, prostate-specific antigen.