Delayed Imaging Improves Lesion Detectability in [ 99m Tc]Tc-PSMA-I&S SPECT/CT in Recurrent Prostate Cancer

Our objective was to compare the ability to detect histopathologically confirmed lymph node metastases by early and delayed [ Tc]Tc-PSMA-I&S SPECT/CT in early biochemically recurrent prostate cancer. We retrospectively analyzed 222 patients selected for radioguided surgery using [ Tc]Tc-PSMA-I&S SPECT/CT at different time points after injection (≤4 h and >15 h). In total, 386 prostate-specific membrane antigen (PSMA) PET predetermined lesions were analyzed on SPECT/CT using a 4-point scale, and the results were compared between early and late imaging groups, with uni- and multivariate analyses performed including prostate-specific antigen, injected [ Tc]Tc-PSMA-I&S activity, Gleason grade group, initial TNM stage, and, stratified by size, PSMA PET/CT-positive lymph nodes. PSMA PET/CT findings served as the standard of reference. [ Tc]Tc-PSMA-I&S SPECT/CT had a significantly higher positivity rate for detecting lesions in the late than the early imaging group (79%, = 140/178, vs. 27%, = 12/44 [