Characteristics of secondary tumors in patients with multifocal prostate cancer and its implications in focal therapy: A study of 102 whole mount robotic radical prostatectomies

Background: Focal therapy protocols often target the dominant tumor nodule (T1) as those are often implicated in progression of the disease. Prostate cancer is often multifocal and some of these tumors may not be treated during focal therapy. The aim of our study is to determine the characteristics of these secondary tumor nodules (T2) on whole mount robotic radical prostatectomy to help define focal therapy protocols. Design: A total of 102 consecutive robotic radical prostatectomy (RRP) performed at a single institution were reviewed. Pathologic data recorded on each tumor nodule included Grade group (GG), tumor size, location, distance to prostate capsule, and distance from the margin. Overall pT stage, tumor volume (TV), margin and lymph node status were noted. Results: Age ranged from 45 -78 years with mean of 63 years. 68 (67%) cases had multifocal disease (average 2 tumors). 1. Of the 68 cases with multiple tumors, two thirds (n = 41) of secondary tumors showed Grade group 2 or higher and one third (n = 27) showed Grade group of 1. Table 1 summarizes the Grade group of all the tumors. 2. The volume of the dominant nodule was significantly larger than that of secondary nodules (p-v=0.015). 3. The distance of the dominant nodule to the capsule is smaller than in the second nodule 0.7 ± 1.2 mm (p=0.002) (Table 2). 4. Distribution of size of secondary nodules is provided in Table 3. 5. More than half of the secondary nodules involved the mid location, followed by one third cases involving the apex and a minority of cases involving the base. More than two thirds of these tumors involved the posterior half of the prostate gland. Numbers indicate counts of cases with that particular GG. Number of cases with a tertiary Grade is indicated within parentheses. T1wo: T1 nodule among cases without T2, T1w: T1 nodule among cases with T2 Conclusions: 1. Two thirds of secondary tumor nodules are clinically significant based on Grade groups and warrant treatment. Although dominant tumor nodules are significantly larger than secondary nodules, we noted vast majority of secondary nodules to be greater than 0.5 cc in volume. 2. A significant difference is observed in distance of dominant tumor nodule from capsule compared to secondary nodules and this finding may be useful in more aggressive nerve sparing surgeries and focal therapy protocols were capsular tissue needs to be preserved