[68Ga]Pentixafor PET/CT for staging and prognostic assessment of newly diagnosed multiple myeloma: comparison to [18F]FDG PET/CT

Purpose To evaluate the prognostic performance of [Ga-68]Pentixafor PET/CT at baseline for staging of patients with newly diagnosed multiple myeloma (MM) and to compare it with [F-18]FDG PET/CT and the Revised-International Staging System (R-ISS). Methods Patients who underwent [Ga-68]Pentixafor and [F-18]FDG PET/CT imaging were retrospectively included. Patient staging was performed according to the Durie-Salmon PLUS staging system based on [Ga-68]Pentixafor PET/CT and [F-18]FDG PET/CT images, and the R-ISS. Progression-free survival (PFS) at patient follow-up was estimated using the Kaplan-Meier estimator and compared using the log-rank test. Area under the receiver operating characteristic curve (AUC) was calculated to assess predictive performance. Results Fifty-five MM patients were evaluated. Compared with [F-18]FDG PET, [Ga-68]Pentixafor PET detected 25 patients as the same stage, while 26 patients were upstaged and 4 patients were downstaged (P = 0.001). After considering the low-dose CT data, there was no statistically significant difference in the number of patients classified in each stage using [Ga-68]Pentixafor PET/CT and [F-18]FDG PET/CT (P = 0.091). [Ga-68]Pentixafor PET/CT-based staging discriminated PFS outcomes in patients with different disease stages (stage I vs. stage II, stage I vs. stage III, and stage II vs. stage III; all P < 0.05), whereas for [F-18]FDG PET/CT, there was only a difference in median PFS between stage I and III (P = 0.021). When staged by R-ISS, the median PFS for stage III was significantly lower than that for stage I and II (P = 0.008 and 0.035, respectively). When predicting 2-year PFS based on staging, the AUC of [Ga-68]Pentixafor PET/CT was significantly higher than that of [Ga-68]Pentixafor PET (0.923 vs. 0.821, P = 0.002), [F-18]FDG PET (0.923 vs. 0.752 P = 0.002), and R-ISS (0.923 vs. 0.776, P = 0.005). Conclusions [Ga-68]Pentixafor PET/CT-based staging possesses substantial potential to predict disease progression in newly diagnosed MM patients.