Background: To examine whether diagnostic biopsy (B1), for patients on active surveillance (AS) for prostate cancer, performed at an outside referral centre (external) compared with our in-house tertiary center (internal), increased the risk of re-classification on the second (confirmatory) biopsy (B2).
Methods: Patients on AS were identified from our tertiary center database (1997-2012) with PSA<10, Gleason sum (GS) ⩽6, clinical stage ⩽cT2, ⩽3 positive cores, <50% of single core involved, age ⩽75 years and having a B2. Patients who had <10 cores at B1 and delay in B2 >24 mo were excluded. Depending on center where B1 was performed, men were dichotomized to internal or external groups. All B2 were performed internally. Multivariate logistic regression examined if external B1 was a predictor of re-classification at B2.
Results: A total of 375 patients were divided into external (n=71, 18.9%) and internal groups (n=304, 81.1%). At B2, more men in the external group re-classified (26.8%) compared with the internal group (13.8%) (P=0.008). On multivariate analysis, external B1 predicted grade-related re-classification (odds ratio (OR) 4.14, confidence interval (CI) 2.01-8.54, P<0.001) and volume-related re-classification (OR 3.43, CI 1.87-6.25, P<0.001). Other significant predictors for grade-related re-classification were age (OR 2.13 per decade, CI 1.32-3.57, P<0.001), PSA density (OR 2.56 per unit, CI 1.44-4.73, P<0.001), maximum % core involvement (OR 1.04 per percentage point, CI 1.01-1.09, P=0.02) and time between B1 and B2 (OR 1.43 per 6 months, CI 1.21-1.71, P<0.001).
Conclusion: At our institution, patients on AS who had their initial B1 performed externally were more likely to have adverse pathological features and re-classify on internal B2.