Background: Effective screening and early detection of small volume prostate cancer (PCa) has led to the concept of focal therapy to treat PCa as an organ-sparing, minimally-invasive procedure [e.g. male lumpectomy]. However, traditional dogma of PCa being a heterogeneous and multifocal disease creates concern to the adoption of this approach. We sought to determine the frequency and role of tumor laterality in order to clarify the possibility of hemiablation of the prostate using focal therapy while preserving the contralateral lobe.

Methods: 1184 paraffin embedded radical prostatectomy specimens excised from patients with early stage PCa between 2002 and 2006 were sectioned at 3-mm thickness and stained with hematoxylin-eosin. Pathologic assessment had particular attention to laterality and percentage of tumor involvement (PTI) along with other routine parameters as pT-stage, pathology Gleason Score (pGS), extracapsular extension (ECE), surgical margins (SM). Based on PTI, all cancer foci were ranked from minimal (≤5) to largest (≥15%) PTI. Clinical and pathologic parameters were analyzed using univariate and multivariate methods.

Results: Analysis of frequency of tumors showed that a real “therapeutic window” for focal therapy sequentially decreased with increasing PTI. Completely unilateral cancers were identified in 227 (19.2%) of 1184 patients. 164 (72.2%) of them have had PTI of ≤5, 40 (17.6%)- PTI of 5.1 ≤10, 9 (4.0%)- PTI of 10.1 ≤15 and 14 (6.2%) -PTI of >15, respectively (p<0.0005). African-American men had bilateral cancers more commonly that Caucasian men, e.g. 93.3% vs. 84.2%, respectively (p<0.0005). Univariate analysis suggested significant variables to be race, prostate weight, pT stage, pGS, +SM. However, only race, pGS, PTI and +SM were independent predictors via multivariate logistic regression (p≤0.05).

Conclusions: This study suggests that only a select group of men diagnosed with prostate cancer have small volume, completely unilateral cancers that would be amenable to focal ablation therapy targeting 1 lobe. Further study is needed to develop predictive models for those patients likely to have small, unilateral cancers amenable to focal therapy.