The PROTEUS Trial: Perioperative Apalutamide Shows Positive Results for Prostate Cancer

The PROTEUS phase 3 trial, published in the New England Journal of Medicine, shows that adding perioperative apalutamide to androgen-deprivation therapy significantly improves outcomes for men with high-risk localized or locally advanced prostate cancer undergoing radical prostatectomy. The international trial randomized 2,109 patients to six cycles of ADT plus apalutamide (240 mg daily) or ADT plus placebo before surgery, then another six cycles after prostatectomy with pelvic lymph-node dissection. Both co-primary endpoints were met with strong statistical significance.

The pathologic endpoint, defined as pathological complete response or minimal residual disease (ypT2 or lower with tumor ≤5 mm), was achieved in 8.9% of patients on apalutamide versus 1.0% on placebo (odds ratio 10.17, P<0.001). Metastasis-free survival, assessed by conventional imaging or PSMA PET, also improved: five-year metastasis-free survival was 78.2% with apalutamide versus 73.5% with placebo (hazard ratio 0.80 for distant metastasis or death, P=0.02). Results were presented at ASCO 2026 and now appear in NEJM.

Secondary endpoints consistently favored ADT plus apalutamide. Event-free survival, time to first subsequent treatment, and time to distant metastasis were all significantly longer with apalutamide (P<0.001 for all), with an approximately 33-month delay in time to subsequent therapy. This is important because earlier neoadjuvant trials often showed better pathology without clear hard-outcome benefits; PROTEUS pairs strong pathologic responses with a demonstrable reduction in metastasis or death.

Eligible patients had newly diagnosed localized or locally advanced adenocarcinoma, ECOG 0–1, and were candidates for radical prostatectomy plus pelvic lymph-node dissection. High-risk features included aggressive grade and substantial core involvement. Men with distant metastases were excluded, so the data best apply to fit surgical candidates with biologically aggressive but nonmetastatic disease rather than average intermediate-risk patients.

Safety was higher in the apalutamide arm. Grade 3 or 4 adverse events occurred in 39.6% versus 31.0% on placebo, driven primarily by a higher incidence of rash. The regimen required stopping apalutamide two weeks before surgery and resuming it four weeks after surgery if postoperative imaging was negative for metastatic disease.

Clinically, PROTEUS supports a new perioperative strategy for men already planned for prostatectomy. Where neoadjuvant ADT alone has historically shown limited pathologic benefit, adding an androgen-receptor pathway inhibitor produces a large increase in major pathologic response and a meaningful reduction in metastatic progression. The 4.7 percentage-point absolute gain in five-year metastasis-free survival may seem modest, but the 20% relative reduction in risk of metastasis or death is clinically relevant in a population with up to 50% relapse within five years after prostatectomy alone.

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