Residual Tumor Potentially Left Behind After Local Ablation Therapy in Prostate Adenocarcinoma

Purpose: We examined contralateral prostate cancer potentially left behind by focal therapy. Materials and Methods: We investigated 100 completely embedded radical prostatectomy specimens in which needle biopsy predicted limited disease (less than 3 positive cores, 50% or less involvement of any positive core, Gleason score 6 or less) and all positive needle cores were unilateral. Clinical stage was T1c in 85 and T2a in 15 cases with the palpable lesion on the positive biopsy side. Results: There was 1 positive core in 66 cases. On average 13.9% of each positive core was involved with tumor. The mean number of separate tumor nodules per radical prostatectomy was 2.9. In 65 radical prostatectomy specimens there was some tumor contralateral to the positive biopsy side. Total tumor volume in the radical prostatectomy contralateral to the positive biopsy side averaged 0.2 cm³ (largest 1.3). In 23 cases contralateral tumor volume was greater than biopsy positive side tumor volume. There were 13 cases in which more than 0.5 cm³ cancer was contralateral to the positive biopsy and 7 with predominantly anterior tumor. Volume contralateral to positive biopsy side could not be predicted by the number of positive cores (1 vs 2) or maximum percent of the core involved. Gleason pattern 4, extraprostatic extension or positive margins were seen contralateral to the positive biopsy side in 13, 1 and 2 cases, respectively. Conclusions: In a highly selected population with limited unilateral biopsy cancer, tumor contralateral to the positive biopsy side at radical prostatectomy is typically small. However, 20% of radical prostatectomy specimens had some contralateral adverse pathology in terms of size, extraprostatic extension, grade or margins.