Body composition metrics and clinical outcomes for patients with metastatic castration-resistant prostate cancer (mCRPC) treated with lutetium-177–PSMA-617.

241 Background: Lutetium-177 ( 177 Lu)–PSMA-617 is a radioligand therapy that can improve outcomes for patients with mCRPC; however, responses are variable. We assessed the prognostic value of body composition metrics for patients treated with 177 Lu–PSMA-617. Methods: We conducted a retrospective review of 163 patients with mCRPC treated with 177 Lu–PSMA-617 at the Emory Winship Cancer Institute. The computed tomography (CT) component of baseline prostate-specific membrane antigen positron emission tomography-CT before initiation of 177 Lu–PSMA-617 therapy was analyzed with Slice-O-Matic software (version 5.0). Univariate and multivariate Cox proportion models were used to assess survival outcomes. Results: Median patient age was 73 (IQR: 65-80); 84% of patients had been treated with taxane-based chemotherapy. Median overall survival (OS) was 15 months (95% CI: 13-22), median progression-free survival (PFS) was 6 months (95% CI: 5-8), and 55% of patients had a reduction in prostate-specific antigen ≥50% (PSA50). Body mass index (BMI) decline during treatment was independently associated with an increased risk of disease progression and a 2.35-fold increased hazard of death on multivariate analysis (PFS HR=1.75, 95% CI=1.06-2.91, p=0.03; OS HR=2.35, 95% CI: 1.08–5.09, p=0.03). The associations between body composition metrics and PSA50 response, PFS, and OS on multivariate analysis that controlling for patient age, race, prior taxane use, number of prior lines of therapy, and baseline PSA are displayed in Table 1. Conclusions: A decline in BMI during treatment with 177 Lu–PSMA-617 is associated with shortened PFS and OS. Higher visceral adipose tissue index (VATI)/subcutaneous adipose tissue index (SATI) is associated with shortened OS, while higher SATI/skeletal muscle index (SMI) is associated with prolonged survival. Higher SATI, SMI, and BMI displayed a trend towards improved outcomes. Association of body composition metrics and PSA50 response, PFS, and OS in patients treated with 177 Lu–PSMA-617. Body Composition Metric N PSA50 Odds Ratio (95% CI), p PFS Hazard Ratio (95% CI), p OS Hazard Ratio (95% CI), p Baseline BMI 25 and 30 - - - SATI/SMI >1.62 1.40 (0.68-2.88) p=0.356 0.87 (0.58-1.30) p=0.493 0.50 (0.28-0.89) p=0.019* 0.64 0.78 (0.38-1.64) p=0.519 1.36 (0.89-2.07) p=0.157 2.62 (1.34-5.11) p=0.005* 38.5 0.81 (0.38-1.71) p=0.58 1.54 (1.00-2.39) p=0.052 1.42 (0.77-2.63) p=0.263 1.62 1.45 (0.68-3.09), p=0.333 0.87 (0.58-1.30) p=0.493 0.57 (0.32-1.02) p=0.06 47.4 2.59 (0.97-6.91), p=0.058 0.71 (0.42-1.21) p=0.212 0.51 (0.23-1.13) p=0.097