medwireNews: Supplementing androgen deprivation therapy (ADT) with 2 years of an abiraterone acetate-based regimen significantly boosts the survival of men with high-risk nonmetastatic prostate cancer, show STAMPEDE results.
Both metastasis-free survival (MFS) and overall survival (OS) were significantly prolonged with the addition of abiraterone, and this “should be now considered a new standard of care” for this patient population, investigator Gerhardt Attard, from University College London in the UK, told the ESMO Congress 2021 delegates.
The team conducted a pooled analysis of two comparisons in the multi-arm, multi-stage STAMPEDE trial to evaluate the impact of intensifying ADT with abiraterone-based therapy in men with node-positive or high-risk node-negative nonmetastatic disease. Participants were randomly assigned to receive ADT with or without abiraterone 1000 mg/day plus prednisolone 5 mg/day or to receive ADT with or without abiraterone, prednisolone, and enzalutamide 160 mg/day for 2 years.
In the combined analysis of both comparisons – conducted at a median follow-up of 72 months – the risk for distant metastases or death was a significant 47% lower for men who did versus did not receive an abiraterone-based regimen, with 6-year MFS rates of 82% and 69%, respectively.
OS was similarly significantly improved with the addition of abiraterone-based therapy to ADT, with a reduction in the risk for death of 40%, and a 6-year OS rate of 86% in the abiraterone group and 77% in the control group.
The presenter highlighted that the MFS and OS results were similar when the two comparisons were analyzed separately.
Adding abiraterone-based therapy to ADT also significantly improved prostate-cancer specific survival and progression-free survival, with hazard ratios relative to ADT alone of 0.49 and 0.44, respectively.
Attard reported on the safety during the first 2 years, when patients were receiving treatment, noting that the use of enzalutamide alongside abiraterone was associated with “increased toxicity.” Specifically, the rate of grade 3–4 adverse events (AEs) was 57% in the abiraterone plus enzalutamide group and 37% in the abiraterone group, compared with rates of 32% and 29% in the respective control ADT-only groups.
There were four deaths due to AEs in the abiraterone plus enzalutamide arm – two cases each of septic shock and sudden death – and three in the abiraterone arm, including one case each of rectal adenocarcinoma, pulmonary hemorrhage, and respiratory disorder. There were no AE-related deaths in the ADT alone arms.
Attard drew attention to the limitations of the analysis, including a lack of information on long-term complications beyond 2 years and an under-representation of relapsed patients, who formed just 3% of the population.
He also added that there are “no data on treatment durations other than 2 years; shorter may be as good, longer may be more effective.”
Eleni Efstathiou (Houston Methodist Cancer Center, Texas, USA), who discussed the presentation, described the findings as “practice changing” for a population with unmet need and for whom the standard of care has remained “stagnant” for over a decade.
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ESMO Congress 2021; 16–21 September