1498 ACTIVE SURVEILLANCE PROSTATE RE-BIOPSY SCHEMA: RESULTS OF ROUTINE TRANSITION ZONE BIOPSIES

Abstract

INTRODUCTION AND OBJECTIVES: Prostate re-biopsy schema for most published active surveillance (AS) cohorts is based on a standard extended template sampling the peripheral zone (PZ). In an AS population, we investigate the effect of routine transition zone (TZ) biopsy by examining the amount of TZ cancer found and its subsequent impact on pathological re-classification. METHODS: Patients were identified from our tertiary referral centre AS database (1997-2012). Eligibility criteria included PSA 10, clinical stage 2, Gleason score (GS) 6, number of positive cores (PCore) 3, no single core 50% involved, age 75 years and at least 1 prostatic re-biopsy after diagnosis. Biopsies of the TZ were taken routinely after the diagnostic biopsy (B1). By mapping location of all PCores found, patients with cancer and pathological re-classification in the TZ could be identified at each AS biopsy. As the number of TZ cores taken is usually limited to 1-2, pathological re-classification for TZ cancers was defined as GS 7 and/or 50% single core involved. Number of PCores was not used. Logistical regression was performed to identify features at diagnostic biopsy that could predict TZ-only reclassification on the 2nd, otherwise known as the confirmatory biopsy (B2). RESULTS: The frequency of cancer, and reclassification, found in the TZ during subsequent biopsies during AS is shown in Table 1. At each re-biopsy, there was a consistent proportion of men that had TZ cancer detected (13.5-16.6%), and TZ re-classification (7.1-9.8%). After excluding men who re-classified in both TZ and PZ, the frequency of TZ-only re-classification at each biopsy was 4.8-8.4%. There was a total 64 TZ-only re-classification events in our cohort. Breakdown of re-classification type was: 50% single core involved (n 47), GS 7 (n 12), both criteria (n 5). Of the 17 men with TZ grade-related re-classification, most were GS 3 4 (n 15), with few GS4 3 (n 1) and GS 4 4 (n 1). On univariate analysis, only % of core involved at B1 was predictive of TZ-only re-classification at B2 (OR1.04, 1.01-1.09, p 0.008). CONCLUSIONS: Routine TZ biopsy during AS detects cancer in 15% of men at each biopsy. However, only 5% of men at each biopsy re-classify in only in the TZ, and most of these are with GS 3 4 disease. Our results suggest TZ biopsy could be performed less frequently or even not performed at all during routine AS re-biopsy. Frequency of TZ cancer and TZ re-classification found at each subsequent biopsy during AS