Defining the index lesion for salvage partial gland ablation after radiation therapy for localized prostate cancer.

Abstract

105 Background: Our objective was to evaluate the impact of MRI and systematic biopsy characteristics to identify the index lesion for salvage partial gland ablation using tumor maps from whole mount slides of salvage radical prostatectomy (sRP) specimen. Methods: We identified 225 patients who underwent sRP between 2000 and 2014 and a tumor map was created from whole-mount slides in 77 patients. Among these patients, we selected men with a priori pre-treatment criteria considered eligible for PGA, including, biopsy proven unilateral disease concordant with a region of interest (ROI) on MRI, and excluding men with imaging suspicious for extra-capsular extension (ECE), seminal vesicle Invasion (SVI) or lymph node involvement (LNI). We describe the correlation between pre-treatment clinical characteristics and final radical prostatectomy whole mount specimen to select men eligible for PGA defined as hemi-gland ablation. Results: Among 77 patients with a tumor map of entirely-submitted and whole-mounted specimens, 15 patients were determined to be eligible for partial gland ablation based on pre-treatment clinical characteristics. The mean age was 60 years and median time from primary RT was 48 months. The median (IQR) tumor volume of the index lesion was 0.3 (0.4) cc. The location of the index lesion was determined to be the apex, mid-gland and base in 77%, 100% and 15% of patients, respectively. The median distance of the index tumor to the urethra was 0.5 (0.2) cm. The index tumor was confined to one lobe and concordant to the biopsy pathology and MRI data in all 15 patients (100%). There was no ECE, LNI or SVI identified in the sRP specimens. To account for those patients who did not have a tumor map of the whole-mount specimen, a sensitivity analysis was performed and determined that the clinical characteristics of the 77 patients with tumor maps were comparable to the entire 225 sRP cohort. Conclusions: Clinical characteristics guided by biopsy findings and MRI data can be used to select men for PGA with recurrent localized prostate cancer after radiation therapy and based on tumor maps from sRP specimen, we propose that salvage hemi-gland ablation including periurethral tissue is feasible.