Prognostic Value of Cycle 1 SPECT SUVmean in Patients with Metastatic Castration-Resistant Prostate Cancer Treated with 177Lu-PSMA-617.

This study aimed to determine whether SPECT SUVmean measured after the first cycle of 177Lu-PSMA-617 is associated with oncologic outcomes in patients with metastatic castration-resistant prostate cancer (mCRPC).

Methods

This retrospective study included 192 consecutive patients with mCRPC treated with 177Lu-PSMA-617 who underwent SPECT 24 h after cycle 1. Associations of total tumor SPECT SUVmean with a decline of 50% or more from baseline in prostate-specific antigen (PSA) levels (PSA50), PSA progression-free survival (PSA-PFS), and overall survival (OS) were evaluated using logistic and Cox regression adjusted for prostate-specific membrane antigen PET SUVmean and scan interval.

Results

Higher SPECT SUVmean quartiles were independently associated with greater odds of PSA50 response (odds ratios of 4.45, 10.2, and 17.1 for quartiles 2 (Q2), 3 (Q3), and 4 (Q4), respectively (P < 0.05 for all), longer PSA-PFS (hazard ratios of 0.52, 0.29, and 0.17 for Q2-Q4, respectively; P < 0.05 for all), and longer OS (hazard ratios of 1.03, 0.82, and 0.42 for Q2-Q4, respectively; P < 0.05 for Q4 only).

Conclusion

SPECT SUVmean measured after the first cycle of 177Lu-PSMA-617 in patients with mCRPC was prognostic for PSA50 and PSA-PFS, independent of the prostate-specific membrane antigen PET SUVmean, whereas its association with OS was limited and observed only in the highest quartile.