Skeletal muscle radiodensity as an automated survival predictor in men with metastatic castration-resistant prostate cancer undergoing PSMA-targeted radioligand therapy.

PURPOSE: Skeletal muscle radiodensity (SMD) is an emerging imaging-derived marker of muscle quality. Its prognostic relevance in patients with metastatic castration-resistant prostate cancer (mCRPC) undergoing [¹⁷⁷Lu]Lu-PSMA-617 radioligand therapy has not yet been systematically evaluated. This study aims to investigate the prognostic value of SMD derived from routine pretherapeutic PET/CT imaging in a large real-world mCRPC cohort treated with [¹⁷⁷Lu]Lu-PSMA-617.

METHODS

In this single-center study, the largest to date cohort comprising 410 mCRPC patients was analyzed. SMD was quantified automatically from the L3-level CT component of pretherapeutic [⁶⁸Ga]Ga-PSMA-PET/CT using an AI-based segmentation tool. An optimal SMD cut-off (19.26 HU) was determined for survival stratification. Associations with overall survival (OS) were assessed using multivariable Cox regression (univariable and multivariable, adjusted for baseline PSA) and Kaplan-Meier analysis.

RESULTS

Lower SMD was associated with reduced OS (HR 1.87, P<.001). Median OS were significantly shorter in the SMD-low group compared to the SMD-high group (7.6 months vs. 12.2 months; P<.001). This prognostic stratification was seen in both, patients with or without PSA50 or PSA90 response, respectively. SMD correlated with age, albumin, and PSA, but not with BMI.

CONCLUSION

SMD assessed from routine pretherapeutic PET/CT is a non-invasive prognostic biomarker in patients undergoing PSMA-targeted radioligand therapy. Integration of host-derived imaging biomarkers such as SMD with tumor-specific parameters may improve risk stratification, prehabilitation and support future individualized treatment strategies in advanced prostate cancer.