Prognostic Value of Interim PSMA-PET Total Tumor Volume for Overall Survival Within ENZA-p, A Randomized Phase 2 Trial of Enzalutamide Versus Enzalutamide Plus [ 177 Lu] Lu-PSMA-617 (ANZUP1901).
Louise Emmett, Nathan Papa, Oliver Sartor et al.
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In 30 seconds
This ENZA-p sub-study of a randomized phase 2 trial assessed whether interim PSMA-PET total tumor volume (PSMA-TTV) predicts overall survival in men with metastatic castration-resistant prostate cancer receiving enzalutamide, with or without [177Lu]Lu-PSMA-617. Among 152 participants with a 3-month scan, an increase in PSMA-TTV was associated with shorter survival than a decrease (hazard ratio 2.52, 95% CI 1.65-3.85). Higher residual PSMA-TTV at 3 months was also associated with shorter survival, independently of treatment arm and PSA response.
Key findings
- An increase versus decrease in PSMA-TTV at 3 months was associated with lower 2-year survival: 30% (95% CI 17-43) versus 67% (95% CI 56-75).
- Residual PSMA-TTV above versus below the median of 103 ml was associated with lower 2-year survival: 34% (95% CI 23-45) versus 76% (95% CI 64-84).
- The association between higher 3-month PSMA-TTV and shorter overall survival was independent of treatment arm and PSA response.
Why it matters
Interim imaging may provide prognostic information beyond PSA response in this trial population. Identifying patients with increasing or high residual PSMA-TTV could help characterize early treatment response and inform risk assessment, although the findings establish prognostic association rather than benefit from changing treatment based on the scan.
What to keep in mind
This was a sub-study, and 10 of 162 randomized participants were not included because they lacked a 3-month PSMA-PET. The authors state that interim PSMA-PET response criteria require further prospective validation.