RT Journal Article SR Electronic T1 Novel framework for treatment response evaluation using PSMA-PET/CT in patients with metastatic castration-resistant prostate cancer (RECIP 1.0): an international multicenter study JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP jnumed.121.263072 DO 10.2967/jnumed.121.263072 A1 Andrei Gafita A1 Isabel Rauscher A1 Manuel Weber A1 Boris Hadaschik A1 Hui Wang A1 Wesley Robert Armstrong A1 Robert Tauber A1 Tristan R. Grogan A1 Johannes Czernin A1 Matthew B. Rettig A1 Ken Herrmann A1 Jeremie Calais A1 Wolfgang A. Weber A1 Matthias Benz A1 Wolfgang P. Fendler A1 Matthias Eiber YR 2022 UL http://jnm.snmjournals.org/content/early/2022/04/14/jnumed.121.263072.abstract AB Purpose: To develop a novel framework for Response Evaluation Criteria In PSMA-PET/CT (RECIP) 1.0 and a composite response classification which combines responses by PSA measurements and by RECIP 1.0 (PSA+RECIP). Methods: This was an international, multicenter, retrospective study. 124 men with mCRPC who underwent 177Lu-PSMA therapy and received PSMA-PET/CT at baseline (bPET) and at interim at 12 weeks (iPET) were included. Pairs of bPET and iPET were interpreted by consensus among three blinded readers for appearance of new lesions. Tumor lesions were segmented and total PSMA-positive tumor volume (PSMA-VOL) was obtained. Appearance of new lesions and changes in PSMA-VOL were combined to develop RECIP 1.0, which was defined as: complete response (RECIP-CR: absence of any PSMA-ligand uptake on iPET), partial response (PSMA-PR: decline ≥30% in PSMA-VOL and no appearance of new lesions), progressive disease (RECIP-PD: increase ≥20% in PSMA-VOL and appearance of new lesions), stable disease (RECIP-SD: any condition but RECIP-PR or RECIP-PD). Changes in PSA levels at 12 weeks by PCWG3 were recorded. Responses by PSA+RECIP were defined as: response (PSA decline ≥50% or RECIP-PR/CR) and progression (PSA increase ≥25% or RECIP-PD). Study's primary outcome measure was the prognostic value of RECIP 1.0 for overall survival (OS). Secondary outcome measure was the prognostic accuracy (C-index) of PSA+RECIP vs PSA responses. Results: Patients with progressive disease (RECIP-PD; n = 39; 8.3 mo) had shorter OS compared to patients with stable disease (RECIP-SD; n = 47; 13.1 mo; p<0.001) and to those with partial response (RECIP-PR; n = 38; 21.7 mo; p<0.001). PSA+RECIP had superior C-indices in identifying responders and progressors compared to PSA only: 0.65 vs 0.62 (P = 0.028) and 0.66 vs 0.63 (P = 0.044), respectively. Conclusion: PSMA-PET/CT by RECIP 1.0 is prognostic for OS and can be used as an early response biomarker to monitor efficacy of 177Lu-PSMA in men with mCRPC. PSA+RECIP may be used as a novel composite endpoint in mCRPC clinical trial design.