Anger SPECT monitoring of 177LuLu-prostate-specific membrane antigen (PSMA) therapy provides significant prognostic information about patients with metastatic castration-resistant prostate cancer (mCRPC) but with 36- to 90-min recording times and partial body coverage. This study assesses the prognostic information from a comprehensive analysis of tumor changes from the first to the last 177LuLu-PSMA therapy injections, as provided by whole-body 177LuLu SPECT recordings from a high-speed 360° cadmium-zinc-telluride (CZT) camera of mCRPC patients. Methods: We included mCRPC patients treated by 177LuLu-PSMA-617 injections who underwent 68GaGa-PSMA-11 PET before treatment, whole-body 360° 177LuLu CZT SPECT recordings of only 18 min obtained 24 h after each 177LuLu-PSMA therapy injection, and plasma prostate-specific antigen (PSA) measurements before each injection. We used Cox proportional hazards models to predict overall survival (OS) according to PSA evolution during treatment, as well as tumor SUVmax, SUVmean, total uptake volume, and total lesion activity (TLA; total uptake volume × SUVmean) extracted from 68GaGa-PSMA-11 PET and the first and last 177LuLu SPECT scans. Results: We included 72 patients with a median age of 71 y (interquartile range, 64-77 y), treated with up to 6 177LuLu-PSMA injections. Among 57 patients with at least 2 177LuLu-PSMA treatment cycles, 35 (61%) died during a follow-up of 12.0 mo (range, 4.9-17.5 mo) from the last 177LuLu-PSMA injection. Most PSA, PET, and SPECT variables were significant univariate predictors of OS. However, only 2 177LuLu SPECT variables were selected as multivariate predictors: SPECT detection of new bone lesions during treatment (P < 0.0001) and final SPECT TLA (P = 0.0007). Means of survival times were 19.7 mo (95% CI, 16.6-22.8 mo) in the 19 patients who showed no new bone lesions and final TLA lower than the median of 750 mL·SUV, 14.4 mo (95% CI, 10.9-18.0 mo) in the 19 patients with only 1 of these 2 criteria, and 6.9 mo (95% CI, 4.5-9.6 mo) in the 19 patients with neither criterion. Conclusion: A comprehensive analysis of tumor changes from the first to the last 177LuLu-PSMA injections, obtained with fast whole-body 360° 177LuLu CZT SPECT recordings, provides strong prognostic information about mCRPC patients, outperforming conventional OS predictors such as PSA evolution and 68GaGa-PSMA-11 PET variables before treatment.
Kunsch et al. (2025) studied this question.