ASCO GU 2023: Time Interval Between Radium‑223 Therapy and Lutetium-177–prostate-Specific Membrane Antigen (177Lu-PSMA) Treatment and Outcomes in the RALU Study

( On the first day of the American Society for Clinical Oncology (ASCO) Genitourinary Cancer Symposium 2023 focussing on prostate cancer, Dr. Kambiz Rahbar presented data from the RALU trial in Poster Session A, examining the association between the time interval between sequential treatment with radium‑223 (223Ra) therapy and Lutetium-177–prostate-specific membrane antigen (177Lu-PSMA) and subsequent outcomes.

Based on the phase III ALSYMPCA and VISION trials, both 223Ra and 177Lu-PSMA-617, respectively, have been shown to improve overall survival in patients with mCRPC, though in somewhat different clinical settings. RALU is an observational, retrospective study that sought to evaluate safety and clinical outcomes of sequential 223Ra/177Lu-PSMA therapy in patients with mCRPC. In data presented here, the authors evaluated the association of time interval between 223Ra and 177Lu-PSMA treatments and safety and OS outcomes of 177Lu-PSMA

The RALU study retrospectively collected data from 2021–22 in German nuclear medicine centers for all patients receiving 177Lu-PSMA with prior history of 223Ra therapy. The authors categorized patients based on the time intervals between the last 223Ra dose and the first 177-Lu-PSMA dose as Group 1 (<6 months) or Group 2 (≥6 months).


Among 132 included patients, 42 received 177Lu-PSMA within 6 months after 223Ra (Group 1) and 90 patients received 177Lu-PSMA ≥6 months following 223Ra (Group 2). Baseline characteristics prior to 177Lu-PSMA therapy were, respectively: median ages 72 and 74 years; 57% and 63% with Eastern Cooperative Oncology Group performance status (ECOG PS) 1, 43% and 37% with ECOG PS 2. In terms of tumor characteristics, the median prostate-specific antigen (PSA) values were 366 and 268 ng/ml, and median alkaline phosphatase (ALP) values were 133 and 149 U/L. Prior to 177Lu-PSMA, 24% and 29% of patients had visceral metastases. In terms of prior therapy, 40% and 64% had received 4 or more life prolonging therapies before starting 177Lu-PSMA. Based on the inclusion criteria, all patients had prior 223Ra of whom 57% and 77% received six 223Ra injections. Additional prior therapies included abiraterone (60%, 77%), enzalutamide (50%, 78%), docetaxel (71%, 76%) and cabazitaxel (17%, 26%).

In Groups 1 and 2, 45% and 52% of patients, respectively, received ≥4 177Lu-PSMA cycles. From the initiation of 177Lu-PSMA start up to 30 days following the last dose, 71% and 82% of patients had treatment-emergent adverse events (TEAEs) of any grade, the most common of which were fatigue (12%, 7%), nausea (12%, 8%) and dry mouth (7%, 18%). During this time period, 36% and 24% of patients had grade 3–4 TEAEs. After excluding laboratory abnormalities, osteonecrosis of the jaw was the most frequent grade 3–4 TEAE (5%, 2%). Treatment-related deaths were reported for 2% and 4% of patients while AEs led to treatment delays in 10% and 9% of patients.


The median OS from start of 177Lu-PSMA was 12.0 months (95% CI, 8.8–19.9) in Group 1 and 13.2 months (95% CI, 10.0–15.9) in Group 2.

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During 177Lu-PSMA therapy, PSA response ≥50% occurred in 53% and 39% and ALP response ≥30% in 28% and 14% of patients in Groups 1 and 2, respectively.

Thus, the authors concluded that these real-world data from the RALU study demonstrate that treating patients with 177Lu-PSMA within 6 months of completing 223Ra was clinically feasible and well tolerated, without differential survival outcomes.

Presented by: Kambiz Rahbar, MD, Department of Nuclear Medicine, University Hospital Münster

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The Association Between the Time Interval Between Sequential Treatment With Radium-223 Therapy and 177Lu-PSMA in the RALU Study - Kambiz Rahbar