Prognostic 18F-flotufolastat PET parameters for outcome assessment of 177Lu-labeled PSMA-targeted radioligand therapy in metastatic castration-resistant prostate cancer

Abstract

Purpose

This retrospective analysis evaluates baseline ¹⁸F-flotufolastat positron emission tomography (PET) parameters as prognostic parameters for treatment response and outcome in patients with metastatic castration-resistant prostate cancer (mCRPC) undergoing treatment with [¹⁷⁷Lu]Lu-PSMA-I&T.

Methods

A total of 188 mCRPC patients with baseline ¹⁸F-flotufolastat PET scans were included. Tumor lesions were semiautomatically delineated, with imaging parameters including volume-based and standardized uptake value (SUV)-based metrics. Outcome measures included prostate-specific antigen (PSA) response, PSA-progression-free survival (PSA-PFS), and overall survival (OS). Univariate and multivariate regression analyses assessed the impact of baseline imaging and pretherapeutic clinical parameters on outcome. Event time distributions were estimated with the Kaplan-Meier method, and groups were compared with log-rank tests.

Results

Significant prognostic parameters for PSA response and PSA-PFS included log-transformed whole-body SUVmax (odds ratio (OR), 3.26, 95% confidence interval (CI), 2.01–5.55 and hazard ratio (HR), 0.51, 95% CI, 0.4–0.66; both p < 0.001) and prior chemotherapy (OR 0.3, 95% CI, 0.12–0.72 and HR 1.64, 95% CI, 1.07–2.58; p = 0.008 and p = 0.028, respectively). For OS, significant prognosticators were the following log-transformed parameters: number of lesions (HR 1.38, 95% CI, 1.24–1.53; p < 0.001), TTV (HR 1.27, 95% CI, 1.18–1.37; p < 0.001), and ITLV (HR 1.24, 95% CI, 1.16–1.33; p < 0.001), with log-transformed TTV (HR 1.15, 95% CI, 1.04–1.27; p = 0.008) remaining significant in multivariate analysis.

Conclusion

At baseline, SUV-based ¹⁸F-flotufolastat PET metrics (e.g., whole-body SUVmax) serve as significant positive prognosticators for short-term outcomes (PSA response and PSA-PFS). In contrast, volume-based metrics (e.g., TTV) are significant negative prognosticators for long-term outcome (OS), in mCRPC patients treated with [¹⁷⁷Lu]Lu-PSMA-I&T.