The Rate of Clinically Significant Prostate Cancer on Repeat Biopsy after a Diagnosis of Atypical Small Acinar Proliferation: A Systematic Review and Meta-Analysis

Introduction: Atypical small acinar proliferation (ASAP) is detected in approximately 5% of prostate biopsies. Current guidelines recommend a repeat biopsy within 3-6 months after the initial diagnosis. However, clinical significance and outcomes of repeat biopsy are conflicting. Based on this situation, we conducted a meta-analysis to report the rate of clinically significant prostate cancer (csPCa) on repeat biopsy after a diagnosis of ASAP to determine the safety and validity of deferring repeat biopsy. Methods: We searched PubMed, Medline, Web of Science, and Embase databases for articles published until July 2023. Two reviewers independently screened the literature, extracted the data, and assessed the risk of bias for the included studies. Pooled ratios and 95% confidence intervals (CIs) were calculated using Stata 17. Results: Sixteen studies and 1,796 patients were included in the meta-analysis. A total of 553 patients were diagnosed with prostate cancer, and 204 had csPCa. The pooled rate of csPCa on repeat biopsy after ASAP diagnosis was 12.1% (95% CI: 0.09, 0.15), which is a relatively low progression rate. However, we observed heterogeneity among the 16 articles. Subgroup analysis was performed, and patients who underwent repeat biopsy within 6 months according to the guidelines had a lower csPCa incidence (effective size [ES] = 0.09, 95% CI: 0.060, 0.120) than those who underwent biopsy after more than 6 months (ES = 0.221, 95% CI: 0.094, 0.349). Conclusion: Repeat biopsy can be safely deferred for patients diagnosed with ASAP. We believe our results may help improve management strategies and encourage clinicians to choose more patient-friendly or non-invasive diagnostic evaluations.