Login to Access Video or Poster Abstract: MP70-06
Sources of Funding: None

Introduction

There is increasing interest in FA for select cases of PCa. The objective of this study is to provide insights into oncological control following FA.

Methods

59 men who underwent radical prostatectomy (RP) between 2012 and 2016 fulfilled criteria for FA: a single MRI lesion (MRI-L) concordant with biopsy Gleason score (GS) <8, no gross extra-prostatic extension on MRI, no GS>6 or GS 6 core length>5mm contralateral to the single MRI-L on 12 core systematic biopsy. All RP surgical specimens were sectioned transversely every 3mm. The greatest linear dimension, GS and extent of Gleason pattern (GP) 4 of all tumor foci were recorded and related to scale on corresponding 3 mm transverse slice prostate maps. Clinically significant secondary cancers (CSSC) were defined as GS 6>5mm or any GP 4 not detected by mpMRI. The location of these CSSC relative to the MRI-L and the distance from the peripheries of the CSSC and the MRI-L were recorded and used to predict oncological control following theoretic ablation templates (TAT) of MRI-L + 10mm margin or hemi-ablation.

Results

Overall, 29 (49%) of the prostates had at least one CSSC. Of the total 50 CSSC, 15 (30%), 34 (68%) and 1 (2%) were ipsilateral, contralateral and midline to the MRI-L. Of the 50 CSSC, 30 (60%), 16 (32%), and 4(8%) were GS 6 > 5mm, GS 3 +4, and GS >3 + 4 respectively. The median greatest linear dimensions (MGLD) of the GS 6, GS 3 + 4, and GS > 3 + 4 PCa were 7.5mm, 5mm, and 2mm, respectively. The MGLD of the ipsilateral vs contralateral CSSC were not significantly different. Of the 20 CSSC with any GP 4, 10 (50%) exhibited a MGLD < 5 mm. The median GP 4 length in missed CSSCs was 0.8mm (range 0.1-2.4mm). A MRI-L + 10mm margin vs hemi-ablation would leave residual GP4 CSSC in 14 (23.7%) vs. 10 (16.9%) cases (p=.36), respectively

Conclusions

Approximately half of candidates meeting our criteria for FA have CSSC. Since 50% of these CSSC were <5mm, many were not detected by MRI. In addition, the median GP 4 length was only 0.8mm, suggesting that many of these CSSC were of equivocal biological significance. Of the CSSC, 68% were contralateral to MRI-L suggesting similar oncological limitations of TAT of MRI-L + 10mm margin and hemi-ablation. Our study provides compelling evidence that all men undergoing FA require active surveillance for disease both within and outside the AT._x000D_

Funding

None