68Ga-PSMA-11 PET/CT Versus Conventional Imaging for Response Evaluation in Metastatic Castration-resistant Prostate...

Area of Science:

• Nuclear Medicine
• Oncology
• Radiology

Background:

• Accurate response assessment is crucial for metastatic castration-resistant prostate cancer (mCRPC) patients undergoing multiple treatments.
• Conventional Prostate Cancer Working Group 3 (PCWG3) criteria, based on RECIST-1.1, are the current standard for response evaluation.
• 68Ga-PSMA-11-PET/CT shows promise in prostate cancer staging, but its role in response assessment requires prospective validation.

Purpose of the Study:

• To prospectively evaluate 68Ga-PSMA-11-PET/CT-based response criteria (RECIP-1.0, PPP, aPERCIST) against PCWG3 criteria in mCRPC patients.
• To compare the performance of these novel criteria with established PCWG3 standards.

Main Methods:

• Prospective evaluation of mCRPC patients initiating taxane, ARPI, or 177Lu-PSMA-617 therapy.
• 68Ga-PSMA-11-PET/CT and conventional imaging (CECT, bone scintigraphy) were performed at baseline and every 12 weeks.
• Response was assessed using PCWG3, RECIP-1.0, PPP, and aPERCIST criteria.

Main Results:

• Thirty-four mCRPC patients were included. Nonprogression rates at 12 weeks varied: PCWG3 (23.5%), aPERCIST (8.8%), PPP (17.6%), and RECIP-1.0 (23.5%).
• RECIP-1.0 demonstrated the highest inter-reader agreement (κ=0.84).
• PCWG3 nonprogression correlated with significantly better overall survival (OS) (P=0.02). PCWG3-radiorecurrent progression-free survival (rPFS) showed the highest C-index for OS (C=0.72), followed by RECIP-rPFS (C=0.71). RECIP-rPFS was superior for non-ARPI patients (C=0.76), while PCWG3-rPFS was better for ARPI patients (C=0.75).

Conclusions:

• PCWG3 criteria remain the most effective for overall response assessment and for patients treated with ARPIs.
• RECIP-1.0 offers superior prognostic value for patients not receiving ARPIs.
• Larger studies are necessary to confirm these findings and validate the utility of RECIP-1.0 in specific mCRPC subgroups.