STAMPEDE: What the Prostate Cancer Trial Found

A trial built like a tournament

Most trials test one thing. STAMPEDE was designed to test many, and to keep going.

It uses what statisticians call a multi-arm, multi-stage design. New treatment arms are added to a shared control group over time, and arms that are not working are dropped at interim checkpoints rather than running to the end. One control group serves them all, so fewer men are needed and answers arrive sooner.

STAMPEDE is run by the UK Medical Research Council and registered as NCT00268476, also ISRCTN78818544. This page covers one of its arms: adding abiraterone acetate to standard hormone therapy, reported in the New England Journal of Medicine in 2017.

The question

Standard treatment for advanced prostate cancer starts with androgen deprivation therapy, or ADT: lowering testosterone, which prostate cancer cells use as fuel.

It works, and then it stops working. Abiraterone acetate blocks an enzyme called CYP17, cutting off testosterone production in places ADT does not reach, including inside the tumor itself. It was already known to help men whose cancer had relapsed. The question was whether giving it up front, at the start of ADT, would do more.

Who was in it

From November 2011 to January 2014, 1,917 men were randomized 1 to 1 to ADT alone or to ADT plus abiraterone acetate at 1000 mg daily with prednisolone at 5 mg daily. Those were fixed trial amounts. Anyone on abiraterone today follows the prescription their own team wrote.

Those were the trial's amounts. If you are on this pairing, take what your own urology or oncology team prescribed.

Median age was 67. Median PSA was 53 nanograms per milliliter. Just over half, 52%, had cancer that had already spread. Twenty percent had node-positive or node-indeterminate disease without distant spread, and 28% had node-negative disease without spread. Ninety-five percent were newly diagnosed.

Local radiotherapy was required for men with node-negative, nonmetastatic disease and encouraged for those with positive nodes. Our explainer on clinical trial phases covers how trials like this are structured.

What it found

Median follow-up was 40 months.

There were 184 deaths in the combination group against 262 in the ADT-alone group. The hazard ratio was 0.63, with a confidence interval of 0.52 to 0.76. Broken down, the hazard ratio was 0.61 in men with metastatic disease and 0.75 in men without.

The failure-free survival result was larger still. Treatment failure meant the cancer growing on scans, growing clinically, PSA rising, or death from prostate cancer. There were 248 such events in the combination group against 535 with ADT alone, a hazard ratio of 0.29.

That is a very wide margin, and it is why this arm changed practice in the UK and beyond.

What it cost

Serious side effects, graded 3 to 5, occurred in 47% of the combination group and 33% of the ADT-alone group. There were nine grade 5 events, meaning deaths, in the combination group and three in the ADT-alone group.

Abiraterone is taken with a steroid for a reason: blocking CYP17 disturbs other hormones, and prednisolone compensates. The typical problems are raised blood pressure, low potassium, fluid retention and liver enzyme changes, which is why men on it have regular blood tests.

Where prostate cancer stands

American Cancer Society projections, reprinted by SEER, give 333,830 new US prostate cancer diagnoses and 36,320 deaths for 2026. Five-year relative survival across all stages, for 2016 to 2022, is 98.2%.

By stage it is 100.0% for localized disease, 100.0% for regional disease, and 40.1% for distant disease. Sixty-nine percent of cases are localized at diagnosis and 9% are distant. Relative survival compares men with the cancer to men of the same age without it, which is why the first two figures reach 100%.

STAMPEDE enrolled men in the advanced and metastatic groups, where the numbers are very different. These are group statistics over past years and predict nothing for an individual. Our page on prostate cancer covers stages and treatment.

When to get checked

NCI lists these urinary signs as reasons to see a doctor. An enlarged prostate, which is not cancer, causes most of them:

• Trouble starting the flow of urine
• Frequent urination, especially at night
• Trouble emptying the bladder completely
• A weak or interrupted stop-and-go flow

And these, which can appear when prostate cancer is advanced:

• Back, hip or pelvic pain that does not go away
• Breathlessness, unusual tiredness, fast heartbeat, dizziness or pale skin, which can be signs of anemia

Persistent bone pain lasting more than three weeks deserves a same-month appointment, particularly in men over 50. Our guide to prostate cancer screening covers the PSA conversation.

What this trial cannot tell you

• This arm tested abiraterone with prednisolone added to ADT. It does not rank abiraterone against docetaxel or the newer hormonal drugs.
• Median follow-up was 40 months. That is short relative to how long many men live with prostate cancer.
• Serious adverse events were substantially more common with the combination, and there were more grade 5 events. Benefit and harm both grew.
• Entry required advanced or metastatic disease with men mostly newly diagnosed. Nothing here applies to early, localized prostate cancer.
• Trial participants meet specific criteria and are monitored closely, so results may not carry over to everyone with this diagnosis.

Sources

• New England Journal of Medicine (record via PubMed), Abiraterone for Prostate Cancer Not Previously Treated with Hormone Therapy (STAMPEDE) — https://pubmed.ncbi.nlm.nih.gov/28578639/
• ClinicalTrials.gov, NCT00268476 (STAMPEDE) — https://clinicaltrials.gov/study/NCT00268476
• NCI PDQ, Prostate Cancer Treatment (Patient Version) — https://www.cancer.gov/types/prostate/patient/prostate-treatment-pdq
• NCI PDQ, Prostate Cancer Screening (Patient Version) — https://www.cancer.gov/types/prostate/patient/prostate-screening-pdq
• SEER Cancer Stat Facts, Prostate Cancer — https://seer.cancer.gov/statfacts/html/prost.html

How this article was prepared

An AI-assisted editorial system helped prepare this page. No named medical reviewer has reviewed it unless one is listed.

The National Cancer Information Foundation publishes Cancer Explained. This page is for learning. It is not medical advice and does not suggest a test or treatment.

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