Upcoming event

TheraP: A randomised phase II trial of 177Lu-PSMA-617 (LuPSMA) theranostic versus cabazitaxel in metastatic castration resistant prostate cancer (mCRPC) progressing after docetaxel: Initial results (ANZUP protocol 1603)

  • Michael S Hofman,
  • Louise Emmett,
  • Shahneen Kaur Sandhu,
  • Amir Iravani,
  • Anthony M. Joshua,
  • Jeffrey C. Goh,
  • David A. Pattison,
  • Thean Hsiang Tan,
  • Ian D. Kirkwood,
  • Siobhan Ng,
  • Roslyn J. Francis,
  • Craig Gedye,
  • Natalie K. Rutherford,
  • Alison Yan Zhang,
  • Margaret Mary McJannett,
  • Martin R. Stockler,
  • John A. Violet,
  • Scott Williams,
  • Andrew James Martin,
  • Ian D. Davis

Watch also the video on TheraP trail by Prof. Hofman (AU)

 

Background
LuPSMA is a radiolabeled small molecule that delivers therapeutic β-radiation to PSMA-expressing tumors. Encouraging efficacy and safety has been shown in non-randomized studies of mCRPC. TheraP is a randomized phase II trial comparing LuPSMA vs cabazitaxel in men with mCRPC progressing after docetaxel.

Methods
Men with mCRPC, and imaging with 68Ga-PSMA-11 and 18F-FDG PET/CT that confirmed high PSMA-expression and no sites of FDG-positive/PSMA-negative disease, were randomly assigned (1:1) to LuPSMA (6-8GBq q6weeks up to 6 cycles) vs cabazitaxel (20mg/m2 q3weeks up to 10 cycles); stratified by disease burden (>20 vs ≤20 sites), prior novel antiandrogens (NAA; abiraterone or enzalutamide), and study site. The primary endpoint was PSA response rate (PSA50-RR) defined by ≥50% reduction. Secondary efficacy endpoints included PSA-progression-free survival (PSA-PFS) and overall survival (OS). Data cut-off was 31DEC19 at this first pre-specified analysis.

Results
200 (median age 72 y, prior NAA 91%, >20 lesions 78%) of 291 PET screened men were randomised to LuPSMA (N=99) or cabazitaxel (N=101). 17 patients withdrew or died before receiving study treatment (1 LuPSMA vs 16 cabazitaxel). The PSA50-RR was higher in those assigned LuPSMA than cabazitaxel (65/99 [66%; 95%CI 56-75] vs 37/101 [37%; 95%CI 27-46]; P<0.001). At a median follow-up of 11.3 months, LuPSMA significantly improved PSA-PFS (HR 0.63, 95%CI 0.45-0.88, P=0.007; 143 events with next pre-specified analysis planned after 170 events). Efficacy results were similar when analyses were restricted to per-protocol treated men. OS data remains immature (57 deaths). Grade III-IV adverse events (AEs) occurred in 31/98 (32%) LuPSMA-treated men vs 42/85 (49%) in cabazitaxel-treated men. Discontinuations for toxicity occurred in 1/98 (1%) LuPSMA vs 3/85 (4%) cabazitaxel-treated. There were no treatment-related deaths.

Conclusions
In men with docetaxel-treated mCRPC, LuPSMA was more active (PSA50-RR) than cabazitaxel with relatively fewer G3-4 AEs and PSA-PFS favoring LuPSMA. Clinical trial information: NCT03392428.