Response and Toxicity to the Second Course of 3 Cycles of 177 Lu-PSMA Therapy Every 4 Weeks in Patients with Metastatic Castration-Resistant Prostate Cancer.

Background: We investigated the response rate and degree of toxicity of a second course of three cycles of [ ¹⁷⁷ Lu]Lu-PSMA radioligand therapy (PSMA-RLT) every 4 weeks in mCRPC patients.
Methods: Forty-three men (71.5 ± 6.6 years, median PSA 40.8 (0.87-1358 µg/L)) were studied. The response was based on the PSA level 4 weeks after the third cycle. The laboratory parameters before and one month after the last cycle were compared. Kaplan-Meier methods were used to estimate the progression-free survival (PFS) and overall survival (OS), and the Cox regression model was performed to find predictors of survival.
Results: Twenty-six patients (60.5%) exhibited a PSA reduction (median PSA declined from 40.8 to 20.2, range 0.6-1926 µg/L, p = 0.002); 18 (42%) and 8 (19%) patients showed a PSA decline of ≥50% and ≥80%, respectively. The median OS and PFS were 136 and 31 weeks, respectively. The patients with only lymph node metastases survived longer ( p = 0.02), whereas the patients with bone metastases had a shorter survival ( p = 0.03). In the multivariate analysis, only the levels of PSA prior to the therapy remained significant for OS ( p < 0.05, hazard ratio 2.43, 95% CI 1.01-5.87). The levels of hemoglobin (11.5 ± 1.7 g/dL vs. 11 ± 1.6 g/dL, p = 0.006) and platelets (208 ± 63 g/L vs. 185 ± 63 g/L, p = 0.002) significantly decreased one month after cycle three, though only two grade 3 anemia and one grade 3 thrombocytopenia were recorded.
Conclusion: A further intensive PSMA-RLT course is well tolerated in mCRPC patients and associated with promising response rates and OS.