Redefining the Concept of Clinically Insignificant Prostate Cancer

Objective: To assess the risk of biochemical recurrence (BCR) in small low-grade prostate tumors following radical prostatectomy (RP), which are defined as clinically insignificant based on the existing criteria developed by Stamey and Epstein. Materials and Methods: We identified 3784 men who underwent RP in Western Australia from September 1998 to March 2019. These patients had a Gleason sum (GS) of ≤6 or 3+4, prostate confined and negative margins. Pathological data analysis was performed using logistic regression modeling. Results: Median follow-up was 96.8 months. BCR occurred in 110 men (2.91%). There was no statistical difference in the rates of failure for patients with a tumor volume <0.5 mL vs 0.5-2.0 mL when comparing (i) those with Gleason 6, or (ii) those with Gleason 3+4. Furthermore, there was no statistical difference in rates of failure when comparing patients with a tumor volume of ≤2 mL vs >2 mL when the percentage of Gleason pattern 4 was ≤20%. However, once the percentage of Gleason pattern 4 increased to 30%, there was a significant increase in BCR in the larger tumors (> 2 mL). Conclusion: This study did not support either Stamey's or Epstein's criteria of insignificant cancer based on volumes of less than 0.5 mL, GS <7 and confined margin negative disease. No risk free cancer was identified, as all groups demonstrated some risk of BCR. This study redefines the entity of insignificant cancer as rather “low risk” cancer and expands its scope to include smaller tumors with minor Gleason pattern 4 components.