medwireNews: An updated analysis of the ENZAMET trial confirms earlier findings that adding enzalutamide to testosterone suppression provides statistically and clinically meaningful survival improvements in metastatic hormone-sensitive prostate cancer.
The findings were presented by Ian Davis (Monash University, Melbourne, Victoria, Australia) at the 2022 ASCO Annual Meeting in Chicago, Illinois, USA.
He reported that at the first planned interim analysis of ENZAMET, which occurred in 2019 after 235 deaths and a median follow-up of 34 months, individuals who were randomly assigned to receive testosterone suppression plus enzalutamide 160 mg/day (n=563) had a significant 33% lower risk for death than those given testosterone suppression plus a conventional nonsteroidal anti-androgen (NSAA; n=562).
The current, planned analysis occurred after 476 deaths and a median 68 months of follow-up and showed that the risk for death remained a significant 30% lower with enzalutamide versus NSAA.
The 3-year overall survival rates were 80% and 72% in the enzalutamide and NSAA arms, respectively, and at 5 years the rates were 67% and 57%. Median OS was not reached in the enzalutamide arm and was 73.2 months in the control arm.
Of note, participants in the enzalutamide group were treated for a median 57.8 months while those in the NSAA group were treated for a median 22.6 months. There was also substantial crossover, with 49.6% of people in the NSAA arm given enzalutamide and 35.8% given abiraterone following progression. Just over a quarter (26.1%) of people in the enzalutamide arm subsequently received abiraterone.
Exploratory subgroup analyses, which were not tested for statistical significance, suggested that the OS improvements were apparent regardless of baseline disease volume, docetaxel use, and timing of metastases, but individuals with low volume disease and no planned docetaxel derived the greatest benefit.
In this subgroup, the risk for death was 49% lower with enzalutamide than NSAA and the 5-year OS rates were 81% and 66% in the 189 and 190 patients, respectively.
Individuals with low volume, synchronous metastases, who received docetaxel also showed greater benefit than the overall population, with a 43% lower risk for death in the enzalutamide arm than in the NSAA arm and 5-year OS rates of 73% and 57%, respectively.
And Davis noted that even participants with high volume disease who received docetaxel derived some benefit from enzalutamide. In this case, the risk for death was 13% lower with enzalutamide versus NSAA and 5-year OS rates were a respective 54% and 51%.
He also points out that the differences were evident despite relatively high median OS (>60 months) in control group participants who received docetaxel.
Davis concluded that the “planned analysis confirms the benefits of enzalutamide when added to best practice standard-of-care.”
He added: “Enzalutamide should be considered in all patients with metastatic disease and especially in those for whom docetaxel is considered unsuitable or unlikely to be beneficial.”
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