The radium lutetium (RALU) study evaluated the feasibility of sequential α- and β-emitter use in patients with bone-predominant metastatic castration-resistant prostate cancer. This preplanned interim retrospective analysis investigated safety and survival outcomes with Lu-PSMA in patients treated with prior Ra. Forty-nine patients were evaluated. Patients received a median of 6 Ra injections; 59% of patients received at least 4 Lu-PSMA cycles. Most (69%) patients received at least 4 life-prolonging therapies before Lu-PSMA. Common Terminology Criteria for Adverse Events grade 3-4 treatment-emergent adverse events during Lu-PSMA therapy and a 30-d follow-up period included anemia (18%) and thrombocytopenia (2%). Median overall survival was 12.6 mo (95% CI, 8.8-16.1 mo) and 31.4 mo (95% CI, 25.7-37.6 mo) from starting Lu-PSMA or Ra, respectively. Lu-PSMA treatment was well tolerated in patients who had received prior Ra. Ra use before Lu-PSMA is feasible and can be considered for future assessment of the optimal treatment sequence.