Interreader and Intrareader Reproducibility of 18 F-Flotufolastat Image Interpretation in Patients with Newly Diagnosed or Recurrent Prostate Cancer: Data from Two Phase 3 Prospective Multicenter Studies.

Interreader and intrareader reproducibility of ¹⁸ F-flotufolastat PET/CT scans in newly diagnosed and recurrent prostate cancer patients was assessed from masked image evaluations from two phase 3 studies. Methods: ¹⁸ F-flotufolastat PET/CT images of newly diagnosed ( n = 352) or recurrent ( n = 389) patients were evaluated by 3 masked readers. Cohen κ was used to assess pairwise patient- and region-level interreader agreement. Agreement among all readers was assessed using Fleiss κ. Intrareader agreement between the first and repeat read (20% of images, ≥4 wk later) was assessed using Cohen κ. Results: Pairwise interreader agreement was 95% or better (newly diagnosed) and 75% or better (recurrent). The κ coefficients were impacted by the high-agreement-low-κ paradox: Cohen κ ranged from not estimable to 0.55, whereas Fleiss κ was 0.50 (newly diagnosed) and 0.41 (recurrent). Agreement was highest in the prostate of newly diagnosed patients (≥95%) and in the pelvic lymph nodes in recurrent patients (≥87%). Intrareader agreement was 86% or better across both populations. Conclusion: ¹⁸ F-flotufolastat PET/CT images can be reliably interpreted, with a high degree of inter- and intrareader agreement.
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