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Background: Avoiding unnecessary biopsies for men with suspected prostate cancer remains a clinical priority. The recently proposed PRIMARY score improves diagnostic accuracy in detecting clinically significant prostate cancer (csPCa). The aim of this study was to determine the best strategy combining PRIMARY score or MRI reporting scores (Prostate Imaging Reporting and Data System [PI-RADS]) with prostate-specific antigen density (PSAD) for prostate biopsy decision making. Methods: A retrospective analysis of 343 patients who underwent both 68Ga-PSMA PET/CT and MRI before prostate biopsy was performed. PSA was restricted to <20 ng/ml. Different biopsy strategies were developed and compared based on PRIMARY score or PI-RADS with PSAD thresholds. Decision curve analysis (DCA) was plotted to define the optimal biopsy strategy. Results: The prevalence of csPCa was 41.1% (141/343). According to DCA, the strategies of PRIMARY score +PSAD (strategy #1, strategy #2, strategy #6) had a higher net benefit than the strategies of PI-RADS + PSAD at the risk threshold of 8–20%. The best diagnostic strategy was strategy #1 (PRIMARY score 4-5 or PSAD ≥ 0.20), which avoided 38.2% biopsy procedures while missed 9.2% of csPCa cases. From a clinical perspective, strategies with a lower risk of missing csPCa were strategy #2 (PRIMARY score ≥4 or PSAD ≥ 0.15), which avoided 28.6% biopsies while missed 5.7% of csPCa cases, or strategy #6 (PRIMARY score≥3 or PSAD ≥ 0.15), which avoided 20.7% biopsies while missed only 3.5% of csPCa cases. The limitations of the study were the retrospective single-center nature. Conclusions: The combination of PRIMARY score +PSAD allows individualized decisions to avoid unnecessary biopsy, outperforming the strategies of PI-RADS + PSAD. Further prospective trials are needed to validate these findings.