Prognostic value of pretherapeutic 68Ga-PSMA-11-PET based imaging parameters in mCRPC patients treated with PSMA radioligands.

Purpose: This study aims to evaluate the prognostic significance of various previously reported PSMA-PET parameters in patients undergoing ¹⁷⁷Lu-PSMA radioligand therapy (RLT). While individual studies have investigated the prognostic value of one or few of these factors, comprehensive analyses are rare.

Methods: Data of 82 patients undergoing ¹⁷⁷Lu-PSMA-radiologand-therapy (RLT) were analyzed. Total tumor volume (tumor volume), average SUVmean of all tumor lesions (SUVmean) and the quotient of sum of SUVmean of all tumor lesions to SUVmean of the parotid glands (tumor-parotid-ratio; TPR) and of the kidneys (tumor-kidney-ratio; TKR) were included in analysis.

Results: This study showed that a tumor volume of <290.6 ml is associated with a better survival in patients undergoing PSMA-RLT (median PFS: 4.2, median OS: 13.2 months) compared to patients with higher tumor volume (median PFS: 3.4,median OS: 6.2 months; p-value = 0.01 for PFS and <0.001 for OS). The average SUVmean correlated inversely with survival. Patients with a SUVmean > 10.7 had a median PFS of 4.2 and OS of 11.4 months while patients with SUVmean <10.7 had a median PFS of 1.6 and OS of 5 months (p-value <0.001 for both). The assessment of TPR showed no significant difference regarding OS and PFS. TKR showed a better PFS in patients with ratio > 0.33 (p-value 0.009) but no significant difference regarding OS.

Conclusion: The present study confirms that pretherapeutic PSMA-PET before RLT with ¹⁷⁷Lu-PSMA has a prognostic value.