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73 Background: 223Ra and 177Lu-PSMA-617 both prolong overall survival (OS) in different mCRPC settings. The observational, retrospective study, RALU, investigated safety and clinical outcomes of sequential 223Ra/177Lu-PSMA therapy in patients (pts) with mCRPC. This analysis evaluated the association of time interval between 223Ra and 177Lu-PSMA treatments and safety and OS outcomes of 177Lu-PSMA. Methods: Retrospective data were collected from 2021–22 in German nuclear medicine centers for all pts receiving 177Lu-PSMA with prior history of 223Ra therapy. Time intervals were 223Ra dose to first 177Lu-PSMA dose. Results: 42 pts received 177Lu-PSMA within 6 mo after 223Ra (Grp 1) and 90 pts received 223Ra ≥6 mo prior to 177Lu-PSMA (Grp 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; median prostate-specific antigen (PSA) values were 366 and 268 ng/ml, and median alkaline phosphatase (ALP) values were 133 and 149 U/L; 40% and 64% received ≥4 life prolonging therapies before starting 177Lu-PSMA. All pts had prior 223Ra; 57% and 77% received 6 223Ra injections; other prior therapies were abiraterone (60%, 77%), enzalutamide (50%, 78%), docetaxel (71%, 76%) and cabazitaxel (17%, 26%). Prior to 177Lu-PSMA, 24% and 29% of pts had visceral metastases. 45% and 52% of pts received ≥4 177Lu-PSMA cycles. From 177Lu-PSMA start to ≤30 days post last dose, 71% and 82% of pts had treatment-emergent adverse events (TEAEs) of any grade; most common were fatigue (12%, 7%), nausea (12%, 8%) and dry mouth (7%, 18%); 36% and 24% of pts had grade 3–4 TEAEs; excluding laboratory abnormalities, osteonecrosis of the jaw was the most frequent grade 3–4 TEAE (5%, 2%). Grade 3–4 laboratory abnormalities (177Lu-PSMA start to ≤90 days post last dose) are shown; treatment-related deaths were reported for 2% and 4% of pts. AEs led to treatment delays in 10% and 9% of pts. Median OS from start of 177Lu-PSMA was 12.0 mo (95% CI, 8.8–19.9) in Grp 1 and 13.2 mo (95% CI, 10.0–15.9) in Grp 2. During 177Lu-PSMA therapy, PSA response ≥50% occurred in 53% and 39% and ALP response ≥30% in 28% and 14% of pts, respectively. Conclusions: In this real-world setting, treating pts with 177Lu-PSMA within 6 mo of completing 223Ra was clinically feasible and well tolerated: no safety signals or concerns were seen. OS outcomes were similar in pts receiving 177Lu-PSMA 223Ra. [Table: see text]

5044 Background: Darolutamide (DARO), a highly potent and structurally distinct androgen receptor inhibitor, prolonged metastasis-free survival by nearly 2 years and reduced the risk of death by 31% vs placebo (PBO) with a favorable tolerability profile in patients (pts) with nonmetastatic castration-resistant prostate cancer (nmCRPC) in ARAMIS. We present post-hoc analyses of ARAMIS to evaluate the association between metastatic progression with prostate-specific antigen (PSA) and clinical progression and to describe the distribution of metastatic progression between groups. Methods: Pts with nmCRPC were randomized 2:1 to DARO (n=955) or PBO (n=554) while continuing androgen-deprivation therapy. Descriptive analyses were performed using the primary data cutoff (Sept 3, 2018) for the double-blind period. Post-baseline metastases were based on central review of conventional radiographic imaging every 16 weeks. PSA and pain progression were defined per primary analysis ( N Engl J Med. 2019;380:1235-46). Results: Metastatic progression was observed in 13.6% of DARO and 28.5% of PBO pts. Most pts had isolated progression as bone (DARO 46%, PBO 39%) or lymph node (32%; 40%) metastasis (Table). Pts with radiographic progression had shorter median time from initial diagnosis to study treatment (DARO 72.9, PBO 74.4 months) vs the overall ARAMIS population (86.2, 84.2 months). Of all pts with metastatic progression, baseline PSA levels (ng/mL) were similar in DARO (12.6) and PBO pts (15.1); DARO pts had lower median PSA before metastasis (16.7) vs PBO pts (48.0) and median absolute/relative PSA decrease from baseline of -0.7/-3.2% vs an increase for PBO pts of 29.5/181%. PSA progression before metastasis was observed in 55.6% (160/288) of pts, occurring in fewer DARO (45.4%) vs PBO pts (63.9%) (treatment difference 18.5%; nominal 95% CI 6.5%–30.6%). The median time between PSA progression and metastasis was 7.0 months with DARO vs 5.6 months with PBO. Pain progression before metastatic progression was rare and similar between groups (DARO 16.9%, PBO 17.7%). Conclusions: DARO significantly reduced risk of metastatic progression and improved overall survival vs PBO without changing the pattern of metastatic progression. Many pts with nmCRPC experienced metastatic progression without PSA progression, and pain progression was rare. These results support the use of imaging with PSA monitoring to properly identify disease progression in pts with nmCRPC. Clinical trial information: TBC. [Table: see text]