Can plasma replace tissue for genotyping in mCRPC? Niven Mehra presented PROMPT at #ESMO26 🧬 In 301 matched tissue/plasma pairs, plasma alone found 82% of BRCA/HRR-altered patients and added 4 that tissue missed, so plasma-first with reflex to tissue at low tumor fraction is defensible for PARPi eligibility. PI3K/AKT is different: only 38% were caught, mostly from missed PTEN loss. But PTEN loss seen in plasma was prognostic (HR 2.11 adjusted for ctDNA fraction), while tissue-only loss was not. Report a low-TF plasma result as not informative, not negative. #ctDNA #LiquidBiopsy #ProstateCancer