What the PROTEUS trial means before prostate cancer surgery

Final phase 3 results from the PROTEUS trial were presented at the 2026 ASCO annual meeting and published in The New England Journal of Medicine on May 31, 2026. For men already planning surgery for newly diagnosed high-risk localized or locally advanced prostate cancer, the study gives doctors a stronger reason to discuss adding apalutamide to androgen-deprivation therapy, or ADT, before and after the operation. But it does not mean every person with prostate cancer should get more treatment, and it does not change prostate cancer screening advice. ([nejm.org](https://www.nejm.org/doi/10.1056/NEJMoa2603878?utm_source=openai))

The narrow reader takeaway is this: if radical prostatectomy is already part of your plan and your cancer fits the trial population, PROTEUS is a reasonable conversation starter with your urologist, medical oncologist, and radiation oncologist. It is not a one-size-fits-all answer because this around-surgery use of apalutamide is off-label in the United States, the trial did not include a surgery-alone comparison group, and important tradeoffs remain. ([clinicaltrials.gov](https://clinicaltrials.gov/study/NCT03767244?aggFilters=status%3Anot+rec+enr+act&cond=Advanced+Prostate+Cancer&rank=8&term=phase+3+drug&viewType=Table&utm_source=openai))

What the trial actually studied

According to the published trial and the registry record, PROTEUS was a randomized, double-blind, placebo-controlled phase 3 study in patients with newly diagnosed high-risk localized or locally advanced prostate cancer who were candidates for radical prostatectomy with pelvic lymph-node dissection. A total of 2,109 patients were randomized. Both groups received ADT for 6 cycles before surgery and 6 cycles after surgery. One group also received apalutamide, while the other received placebo. ([nejm.org](https://www.nejm.org/doi/full/10.1056/NEJMoa2603878?rss=searchAndBrowse&utm_source=openai))

That design matters. The trial was not testing apalutamide for all prostate cancer, and it was not built for people choosing radiation instead of surgery, people with low-risk disease, or people with metastatic disease. Readers should be careful not to generalize these results beyond the group that was actually studied. ([clinicaltrials.gov](https://clinicaltrials.gov/study/NCT03767244?aggFilters=status%3Anot+rec+enr+act&cond=Advanced+Prostate+Cancer&rank=8&term=phase+3+drug&viewType=Table&utm_source=openai))

What improved in plain language

In simple terms, more patients who received apalutamide plus ADT had little or no cancer left in the prostate specimen at surgery, and more were alive without metastatic spread at follow-up. The trial reported pathologic complete response or minimal residual disease in 8.9% of the apalutamide group versus 1.0% of the placebo group. The estimated 5-year metastasis-free survival rate was 78.2% versus 73.5%. ([nejm.org](https://www.nejm.org/doi/10.1056/NEJMoa2603878?utm_source=openai))

Those are meaningful findings, but they are not the same as saying the regimen is now the answer for everyone. Most patients in the intensified-treatment group still did not have a pathologic complete response, and long-term questions about cure, later treatment needs, and best patient selection remain. ASCO’s patient summary frames the results as promising for selected people with high-risk disease, not as a universal new standard for every prostate cancer case. ([asco.org](https://www.asco.org/practice-patients/patient-resources/research-summaries/PROTEUS-prostate-cancer?utm_source=openai))

Why caution is still needed

ASTRO, the main U.S. radiation oncology society, urged caution about treating PROTEUS as an automatic practice change. One major reason is the comparator: both groups received ADT, even though surgery alone is a common treatment pathway for localized prostate cancer. So the study does not tell patients whether perioperative apalutamide plus ADT is better than going straight to surgery without systemic therapy. ([astro.org](https://www.astro.org/news-and-publications/news-and-media-center/media-resources/proteus-response))

ASTRO also noted that the metastasis-free survival benefit was driven in part by events found on PSMA PET/CT imaging, and that the manuscript did not show a significant between-group difference when metastasis-free survival was assessed with conventional imaging alone. That does not erase the main result, but it does make interpretation more nuanced when clinicians compare this pathway with other established treatment strategies. ([astro.org](https://www.astro.org/news-and-publications/news-and-media-center/media-resources/proteus-response))

Just as important, the trial does not answer whether the same approach should be used for patients choosing radiation-based treatment instead of surgery. For localized prostate cancer overall, CDC notes that common treatment options can include surgery, radiation therapy, and active surveillance, depending on the case. ([cdc.gov](https://www.cdc.gov/cancer/features/prostate-cancer.html))

Side effects and real-world tradeoffs

Adding more treatment usually means adding more burden. In the published trial, grade 3 or 4 adverse events occurred in 39.6% of patients who received apalutamide plus ADT and in 31.0% of those who received placebo plus ADT, with the difference mainly driven by rash. ([nejm.org](https://www.nejm.org/doi/full/10.1056/NEJMoa2603878?rss=searchAndBrowse&utm_source=openai))

ASTRO’s response also highlighted serious adverse events during the treatment period in 19.3% of the apalutamide group versus 16.4% of the placebo group, along with serious events leading to death in 0.7% versus 0.1%. ASTRO further emphasized that local-therapy harms still matter in real life, including urinary incontinence and erectile dysfunction after surgery. ([astro.org](https://www.astro.org/news-and-publications/news-and-media-center/media-resources/proteus-response))

The current FDA label for ERLEADA lists approved U.S. uses for metastatic castration-sensitive prostate cancer and non-metastatic castration-resistant prostate cancer, not for perioperative treatment around prostatectomy. The same label warns about cerebrovascular and ischemic cardiovascular events, fractures, falls, seizure, severe skin reactions, interstitial lung disease or pneumonitis, and embryo-fetal toxicity. ([accessdata.fda.gov](https://www.accessdata.fda.gov/drugsatfda_docs/label/2024/210951s016lbl.pdf))

For patients and families, that means this decision is about more than improving a trial endpoint. It is also about whether a year of systemic therapy, plus surgery and recovery, fits a person’s age, other health conditions, work and caregiving responsibilities, and tolerance for urinary, sexual, bone, skin, fatigue, and cardiovascular risks. CDC notes that side effects from surgery or radiation for localized prostate cancer can include impotence, loss of bladder control, and bowel problems. ([cdc.gov](https://www.cdc.gov/cancer/features/prostate-cancer.html))

What to ask your care team now

Does my cancer really match the PROTEUS population: newly diagnosed, high-risk localized or locally advanced disease, and already a candidate for radical prostatectomy? ([clinicaltrials.gov](https://clinicaltrials.gov/study/NCT03767244?aggFilters=status%3Anot+rec+enr+act&cond=Advanced+Prostate+Cancer&rank=8&term=phase+3+drug&viewType=Table&utm_source=openai))
If we discuss apalutamide around surgery, would that be off-label at this point in the United States? ([accessdata.fda.gov](https://www.accessdata.fda.gov/drugsatfda_docs/label/2024/210951s016lbl.pdf))
How do surgery-based options compare with radiation-based options in my case, including the chance that I could still need more treatment later? ([cdc.gov](https://www.cdc.gov/cancer/features/prostate-cancer.html))
How would side effects be monitored during treatment, especially rash, falls, fractures, heart or stroke symptoms, seizures, and breathing problems? ([accessdata.fda.gov](https://www.accessdata.fda.gov/drugsatfda_docs/label/2024/210951s016lbl.pdf))
Is there a clinical trial or center-specific protocol available, and would insurance treat this as off-label use? ([clinicaltrials.gov](https://clinicaltrials.gov/study/NCT03767244?aggFilters=status%3Anot+rec+enr+act&cond=Advanced+Prostate+Cancer&rank=8&term=phase+3+drug&viewType=Table&utm_source=openai))

If you are already taking apalutamide or another prostate cancer treatment and develop chest pain, stroke-like symptoms, a seizure, severe rash, or new breathing trouble, seek urgent medical care right away. ([accessdata.fda.gov](https://www.accessdata.fda.gov/drugsatfda_docs/label/2024/210951s016lbl.pdf))

The bottom line

PROTEUS is one of the most important recent surgery-focused prostate cancer trials, and it gives selected high-risk patients a concrete new question to bring to their clinicians. But as of June 22, 2026, in the United States this remains a nuanced, off-label discussion for the right surgery candidate, not a blanket recommendation for all prostate cancer cases. ([nejm.org](https://www.nejm.org/doi/10.1056/NEJMoa2603878?utm_source=openai))

Sources

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This article is for general informational purposes only and is not medical advice. Research findings can be early or incomplete, and health guidance can change. Always talk with a qualified healthcare professional about personal symptoms, diagnosis, medications, vaccines, screenings, or treatment decisions. If you think you may have a medical emergency, call emergency services right away.