Long term survival benefits from adding enzalutamide to testosterone suppression in men with metastatic hormone-sensitive prostate cancer (mHSPC) have been confirmed in the latest update to the Australian-led ENZAMET trial.
Professor Ian Davis of Monash University presented five year data from the trial at ASCO 2022 which confirmed that the benefits seen in the three-year interim analysis were maintained for a further two years.
The trial, conducted by the Australian and New Zealand Urogenital and Prostate Cancer Trials Group (ANZUP), enrolled 1,125 patients with mHSPC, who were randomised to enzalutamide or standard therapy with a nonsteroidal antiandrogen, both in combination with standard testosterone suppression, and with concurrent docetaxel at the investigator’s discretion.
The latest results show that enzalutamide was associated with a 30% reduction in risk of death compared with a standard nonsteroidal antiandrogen in patients with mHSPC receiving testosterone suppression (Hazard Rate 0.70, 95% CI [0.58, 0.84]; P < .0001).
The 5-year overall survival rate was 67% in the enzalutamide arm and 57% in the control group.
Professor Davis noted that while the benefits were more pronounced in patients with low volume disease, the latest analysis also showed signs of benefit in some patients with high volume mHSPC.
The overall HR for overall survival with enzalutamide versus standard therapy was 0.54 for patients with low volume disease and 0.79 for patients with high volume disease.
For M1 patients with high volume disease who received docetaxel the risk of death at five years was 21% lower with enzalutamide compared to standard therapy (HR 0.79).
The study investigators therefore suggested that the greatest benefits of triplet therapy with testosterone suppression, enzalutamide and docetaxel may be in patients with the poorest risk disease, particularly those with synchronous high-volume mHSPC.
The findings provide further support for the early use of enzalutamide in the treatment of metastatic prostate cancer, confirming the interim results presented at a previous ASCO meeting at which clinicians said noted that use of docetaxel was often associated with troublesome side effects.