PSMA-PET identifies PCWG3 target populations with high concordance however superior reproducibility when compared to conventional imaging

Ziel/Aim The primary aim of this study was to investigate the impact of PSMA-PET on PCWG3 clinical subtype classification, frequently used to identify CRPC clinical trial target populations

Methodik/Methods Databases at three participating PET centers were retrospectively screened for patients with prostate cancer who underwent PSMA-PET between 2014 and 2019, had (a) documented CRPC during continuous ADT, (b) PSA values ≥1 ng/mL and (c) conventional imaging (CI) i.e. BS and CT (78 %) or wbMRI (22 % of patients) within 6 months of the PSMA-PET without changes of therapy between the staging modalities. Clinical PCWG3 subtype, i.e. locally recurrent (lrCRPC), nonmetastatic (nmCRPC), nodal spread (nCRPC), bone disease (bCRPC) and visceral disease (vCRPC), was determined for PET versus CI by three independent blinded readers. Inter-reader agreement was assessed by Fleiss’ Kappa

Ergebnisse/Results 67 patients were included with a median PSA level of 53.2 ng/mL (IQR 5.8-334.6 ng/mL). Median time between PSMA-PET and CI was 1 month (IQR 0-2). CI resulted in lr, nm, n, b, vCRPC for 0 % (0/67), 13 % (9/67), 6 % (4/67), 58 % (39/67) and 22 % (15/67) of patients, respectively. Overall, PSMA-PET and CI were concordant in 70 % (47/67) of patients. PSMA-PET led to an up-staging in 15 % (10/67) of patients, all of which were CI nmCRPC. PSMA-PET led to a down-staging in 15 % (10/67) of patients, of these 10 % (7/67) had CI visceral disease ruled out by PSMA-PET. PET vs CI interobserver agreement was 0.81 vs 0.51, 0.80 vs 0.58, 0.95 vs 0.72, or 0.58 vs 0.65 for N, M1a, M1b, or M1c staging, respectively

Schlussfolgerungen/Conclusions In our multicenter, retrospective study PSMA-PET demonstrates high level of concordance with conventional imaging for per-patient PCWG3 clinical subtype. PSMA-PET, which delivers higher reproducibility and more accurate assessment of nmCRPC and visceral disease, should be implemented in future clinical trial protocols

• Literatur/References

• 1 Scher HI, Morris MJ, Stadler WM, Higano C, Basch E, Fizazi K. , et al. Trial Design and Objectives for Castration-Resistant Prostate Cancer: Updated Recommendations from the Prostate Cancer Clinical Trials Working Group 3. J Clin Oncol . 2016; Apr 20; 34 ( (12) ): 1402-1418 .