177Lu-PSMA-617 (LuPSMA) versus cabazitaxel in metastatic castration-resistant prostate cancer (mCRPC) progressing after docetaxel: Updated results including progression-free survival (PFS) and patient-reported outcomes (PROs) (TheraP ANZUP 1603).

Abstract

6 Background: TheraP is a randomized phase 2 trial that showed LuPSMA significantly improved the primary endpoint of PSA≥50% reduction (66% vs. 37%) compared to cabazitaxel in men with docetaxel-treated mCRPC. We now report results on other clinical endpoints and PROs reached the pre-specified target of 170 PFS events. Methods: 200 men with mCRPC (median age 72 y, prior enza/abi 91%) and high PSMA-expression by 68Ga-PSMA-11 and no sites of FDG-positive/PSMA-negative disease, were randomly assigned (1:1) to LuPSMA (6-8.5GBq q6wk up to 6 cycles; N = 99) or cabazitaxel (20mg/m2 q3wk up to 10 cycles; N = 101). Secondary endpoints include PSA/radiologic PFS (PCWG3), pain response (≥2 point reduction on McGill-Melzack Present Pain Intensity scale, objective response rate (ORR) (RECIST 1.1), adverse events (CTCAE), PROs (EORTC QLQ-C30) and overall survival (OS). Cut-off date for analysis of 20JUL20. Results: At a median follow-up of 18.4 months, PFS was significantly longer in those assigned Lu-PSMA rather than cabazitaxel (rates at 1y 19% [95%CI 12-27%] vs 3% [1-9%], hazard ratio (HR) 0.63, 95%CI 0.46-0.86; p = 0.003; 173 events). Similar benefit was seen for rPFS (HR 0.64, 95%CI 0.46-0.88; p = 0.007; 160 events) and PSA-PFS (HR 0.60 95%CI 0.44-0.83; p = 0.002; 172 events). ORR in 78 men with measurable disease was significantly greater in the LuPSMA arm (49% vs 24%, RR 2.1, 95%CI 1.1-4.1; p = 0.019). In 90 men with pain at baseline, pain responses occurred in 60% in the Lu-PSMA arm vs 43% for cabazitaxel (RR 1.42, 95%CI 0.84-4.48; p = 0.10). Patient-reported global health status was similar (LuPSMA 64 [95%CI 61-67] vs cabazitaxel 60 [57-64]) with significantly better outcomes reported for fatigue (34 [95%CI 31-37] vs 40 [36-43]), social functioning (79 [76-82] vs 73 [69-77]), insomnia (24 [20-27] vs 29 [25-33]) and diarrhoea (8.3 [5.6-11.0] vs 15.6 [12.6-18.6]) domains. No PRO domains were superior for cabazitaxel. G3-4 AEs were similar to previously reported (33% vs 53%). OS data remains immature (90 deaths). Conclusions: In men with docetaxel-treated mCRPC, LuPSMA is a promising alternative to cabazitaxel with significantly higher activity (PSA≥50%, PFS, ORR), fewer G3-4 AEs, similar effects on global health status, and improvements in some PRO domains. Clinical trial information: NCT03392428.