Re: ‘Reconciling primary outcomes and statistical power: comment on a randomised controlled trial on prostate biopsy approaches’

We thank McLean et al. [1] for their recent Letter to the Editor, in response to our randomised control trial entitled ‘Prostate cancer detection by MRI-ultrasonography fusion transperineal vs transrectal biopsy: a randomised control trial’ [2]. The authors identified a discrepancy between the primary outcome listed at clinicaltrials.gov (infection) and in our publication (clinically significant prostate cancer [csPCa]). We did not explain this difference in our manuscript due to word count restrictions. Unfortunately, the Appendix S1 (randomised controlled trial [RCT] protocol/Statistical Analysis Plan [SAP] from 2019, revised protocol/SAP from 2021 to 2022) were not made available on-line due to an error during submission. These are now included as Appendix S1 with this letter. Due to delays caused by the coronavirus disease 2019 (COVID-19) pandemic, trial initiation was substantially delayed. As other RCTs were already in progress comparing infection following transrectal (TR) and transperineal (TP) biopsy [3, 4], we amended our primary outcome to csPCa detection. Due to staffing shortages and an oversight by our research office, the protocol on clinicaltrials.gov was not updated. This has now also been corrected, and the study has been formally closed to recruitment (edits performed 11 December 2025 6:57 AM, pending Protocol Registration and Results System [PRS] release by clincaltrials.gov). The authors’ second point concerns our sample size calculation. At the time of our updated power analysis in 2021–2022, we used in-person study comparing TP and TR biopsy that reported csPCa detection rates of 46% and 26%, respectively, corresponding to a relative risk of 1.6 [2]. The prevalence of csPCa was derived from a large retrospective study published from our institution. We used a prevalence of 32% (the adjusted rate accounting for MRI lesion number, Prostate Imaging-Reporting and Data System [PI-RADS] score, and clinical indication). The prevalence of 34% value listed in the manuscript was a copy-and-paste error originating from the SAP, this number does not adjust for clinical indication and includes men with prior negative systematic biopsy, who were excluded from our RCT. As McLean et al. [1] correctly note, using a prevalence of 34% yields a statistical power of 74%; however, using the correct 32% value yields a power of 83% (Appendix S1). We acknowledge that both estimates (32–34%) are substantially lower than the observed csPCa detection rates in our RCT and this difference was interpreted in our original manuscript [2]. Nothing is declared. Appendix S1 Supplementary materials. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.