"To our knowledge, ENACT represents the first trial to compare the effects of a novel androgen receptor antagonist as monotherapy versus AS in patients with low-risk or intermediate-risk localized prostate cancer," the study team says in JAMA Oncology.
"Results suggest that enzalutamide may offer an alternative short-term treatment option for this patient population, potentially reducing the need for more aggressive treatment approaches," write Dr. Neal Shore of Carolina Urologic Research Center in Myrtle Beach, South Carolina, and colleagues.
The open-label study included 227 men (mean age, 66; 90% white) with low- or intermediate-risk localized prostate cancer on AS with 114 randomly allocated to oral enzalutamide 160 mg daily or continued AS alone.
Compared with AS alone, treatment with enzalutamide reduced the risk of pathological or therapeutic prostate cancer progression by 46% (hazard ratio, 0.54; 95% CI, 0.33 to 0.89).
"Patients receiving enzalutamide also had a significant improvement in the odds of a negative biopsy result, as well as significant reductions in the percentage of cancer-positive cores and odds of a secondary rise in serum PSA levels at one year compared with AS," the authors report.
Enzalutamide monotherapy was well-tolerated, with side effects consistent with the known safety profile of enzalutamide.
The authors of an invited commentary note that while outcomes at one year favored enzalutamide, the differences in the two groups at two years appeared "very similar, suggesting that the natural history of the tumor may not have been altered but patients in the enzalutamide arm had different growth kinetics while receiving active enzalutamide treatment."
"Whether this will translate into substantially delaying or abrogating the need for definitive therapy for a cohort of patients will require longer follow-up," write Dr. Susan Halabi of Duke University Medical Center, in Durham, North Carolina, and colleagues.
"While the data are encouraging," they say, "unfortunately the trial falls short in identifying those particular patients who will experience a clinical benefit from early systemic intervention with enzalutamide. It is critical that patients with low-risk or intermediate-risk prostate cancer be followed for at least a decade with studies that are sufficiently powered to detect those differences in outcomes in various subsets of patients."
The ENACT trial was funded by Astellas Pharma Inc and Pfizer Inc, the co-developers of enzalutamide. Dr. Shore received personal fees from both companies during the study.
SOURCE: https://bit.ly/3b5VCO9 JAMA Oncology, online June 16, 2022.
By Reuters Staff
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