High PSMA PET Tumor Volume Halves 5-Year PFS in ENZAMET mHSPC Sub-Cohort

In an ENZAMET substudy, 100 patients received testosterone suppression with either enzalutamide or a control non-steroidal antiandrogen then underwent a semi-automated PSMA total tumor volume (TTV) quantified on baseline PSMA-PET.

The PSMA TTV results strongly stratified metastatic hormone-sensitive prostate cancer: men in the highest quartile (TTV > 71 mL; median 61 mL in CHAARTED-high vs 22 mL in low) had 5-year progression-free survival of 36% versus 61% for lower-volume disease (HR per TTV-doubling 1.19, 95% CI 1.03-1.38, p = 0.011).

Even among patients classified as low volume by conventional CHAARTED criteria, high PSMA-TTV reduced 5-year PFS to 21% versus 57% (p < 0.001); overall-survival differences were smaller (60% vs 74%, HR per doubling 1.10).