Abiraterone (Zytiga), added to long-term hormone therapy, extends survival in very-high-risk localized prostate cancer. It is also toxic and expensive, and clinicians have no reliable way to know which men truly need it. A new analysis of two STAMPEDE phase 3 trials argues that an artificial-intelligence read of a routine biopsy slide can help sort that out — and, importantly, the model was locked before the data were unblinded.
Researchers led by University College London and Artera applied a previously validated multimodal AI (MMAI) model — the ArteraAI Prostate test — to 1,137 men with non-metastatic, clinically very-high-risk disease enrolled in two sequential, non-overlapping abiraterone comparisons within the STAMPEDE platform (NCT00268476). The model combines digitized pathology images with PSA, tumor stage, and age, and used a pre-established 75th-percentile cutoff to split patients into “MMAI very-high-risk” and “standard high-risk” groups. The primary endpoint was metastasis-free survival (MFS) — a composite of time to metastasis or death, which is a surrogate rather than a direct measure of overall survival. In total, 583 men received long-term ADT and 554 received ADT plus abiraterone.
A biomarker that separates benefit from non-benefit
In the MMAI very-high-risk subgroup (N=268), adding abiraterone cut the risk of metastasis or death by more than half — hazard ratio 0.47 (95% CI 0.31–0.70). Five-year MFS rose from 62% (95% CI 53–70%) with ADT alone to 81% (74–87%) with abiraterone. Because MFS is a composite surrogate, this is not the same as a demonstrated overall-survival benefit in this subgroup.
In the larger standard-high-risk group (N=869), the drug added little: HR 0.83 (95% CI 0.63–1.09), with five-year MFS of 82% (78–85%) with ADT alone versus 84% (80–87%) with abiraterone — a small numerical difference that was not statistically significant. The treatment-by-biomarker interaction was significant (p=0.02), and the pattern held in both node-negative and node-positive subgroups.
A locked digital-pathology test predicted abiraterone benefit on metastasis-free survival — a surrogate endpoint — in very-high-risk disease and little benefit in the standard-high-risk group: a hypothesis for prospective testing.
The caveats are real. This is a post-hoc analysis of randomized data, not a prospective biomarker-stratified trial; the endpoint is a surrogate (metastasis or death), not overall survival; the two abiraterone comparisons shared no controls; and the standard-high-risk confidence interval still crosses 1, so a modest benefit there cannot be ruled out. The authors frame the test as a way to “maximize benefit from treatment intensification whilst avoiding unnecessary toxicity” — a hypothesis that a prospective trial would need to confirm before it changes practice.