This exploratory analysis of the PROMIS and PICTURE trials evaluated 306 men with 1–2 suspicious MRI quadrants who underwent 5-mm transperineal template mapping biopsy, comparing MRI-detected vs. MRI-undetected prostate cancers and assessing whether adding systematic biopsies changes focal therapy planning.
MRI-targeted biopsy alone detected all clinically significant cancers (Grade Group ≥2); adding contralateral hemigland biopsy changed focal therapy planning in only 9% (11/127) of eligible patients, with a number-needed-to-biopsy of 12. Full whole-gland biopsy did not significantly improve planning over targeted biopsy (91% unchanged, p=0.1).
Exploratory post-hoc analysis of trial data rather than a prospectively designed study; findings limited to patients with 1–2 suspicious MRI quadrants; prospective validation specifically for focal therapy planning is still needed.
For men eligible for focal therapy, MRI-targeted biopsy alone appears sufficient to detect clinically significant cancer. If additional mapping is desired, adding only contralateral hemigland biopsies — rather than full systematic biopsy — captures the small group (≈9%) who would need a change in treatment template.
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