Key Ideas

Perioperative intensification is reshaping treatment for high-risk localized and metastatic castration-sensitive prostate cancer. The phase 3 PROTEUS trial showed that adding apalutamide to androgen deprivation therapy (ADT) around radical prostatectomy increased in pathologic response and reduced metastatic risk, while TALAPRO-3 demonstrated that talazoparib plus enzalutamide benefits a broader range of homologous recombination repair (HRR)-altered patients than previously appreciated, including, for the first time, those with ATM alterations. Meanwhile, emerging data support cognitive and treatment-burden considerations, including drug selection based on CNS penetration and a growing evidence base for safe treatment discontinuation in select responders.

PROTEUS: Perioperative Apalutamide Sets a New Bar in High-Risk Localized Disease

Despite curative-intent radical prostatectomy, more than half of patients with high-risk localized prostate cancer ultimately relapse with metastatic disease. The phase 3 PROTEUS trial tested whether adding one year of perioperative apalutamide to ADT, six cycles neoadjuvant and six cycles adjuvant, around radical prostatectomy could change that trajectory in a genuinely high-risk population: roughly 95% of enrolled patients had a Gleason score of 8 or higher, 38-40% had a baseline PSA above 20, and 35% had extracapsular extension (T3 disease or higher).

The trial met both dual primary endpoints. Pathologic complete response/minimal residual disease occurred in roughly 9% of patients receiving apalutamide plus ADT versus about 1% with placebo plus ADT, a ninefold improvement. Major pathologic response (less than T2 disease with residual tumor under 5mm) occurred in roughly 30% of patients on the apalutamide arm versus 11% on placebo. On the second primary endpoint, metastasis-free survival assessed by PSMA PET, apalutamide plus ADT reduced the risk of metastasis or death by 20% at one year (hazard ratio 0.80). Event-free survival, PSA progression, recurrence, or death, extended from a median of 38 months with ADT alone to roughly 58 months with apalutamide added, a 29% reduction in risk. Time to first subsequent therapy was delayed from 41 months with placebo to 74 months with apalutamide (hazard ratio 0.65).

Apalutamide's side effect profile in this setting included a distinctive skin rash relative to other androgen receptor pathway inhibitors (ARPIs) like enzalutamide or darolutamide, along with a small increase in seizure risk (0.2% versus 0.1% with placebo), attributable to some degree of CNS penetration. Taken together, one year of perioperative apalutamide plus ADT represents a new standard-of-care option for candidates for radical prostatectomy with high-risk localized or locally advanced disease, alongside existing options such as 2 years of abiraterone with radiation for patients with positive pelvic lymph nodes and high-risk features, and enzalutamide-based approaches in the high-risk biochemical recurrence, non-metastatic setting.

TALAPRO-3: PARP Inhibition Extends Benefit to ATM-Altered Disease

For metastatic castration-sensitive prostate cancer with HRR gene alterations  were found in roughly 25% of patients on next-generation sequencing, the phase 3 TALAPRO-3 trial evaluated talazoparib plus enzalutamide against enzalutamide alone in chemotherapy-naive patients (with no more than three months of prior ARPI exposure allowed before enrollment). The trial met its primary endpoint of progression-free survival, with talazoparib plus enzalutamide reducing the risk of progression or death by 52% (hazard ratio 0.48) compared to enzalutamide alone; the enzalutamide-alone arm had a median PFS of 45 months. Overall survival is trending positive (hazard ratio 0.76) but remains immature.

Benefit held across virtually every subgroup: BRCA1/2 and non-BRCA HRR alterations, site of metastasis, baseline Gleason score, and baseline PSA. The most notable finding was in the ATM subgroup, the second most common HRR alteration behind BRCA2, which showed a favorable response to talazoparib plus enzalutamide. This matters because prior PARP inhibitor trials had not demonstrated a clear ATM benefit, making TALAPRO-3 the first study to show this signal in this genomic subgroup.

As with other PARP inhibitors, bone marrow suppression is a relevant toxicity: 71% of patients experienced anemia requiring dose reductions in this trial, and myelodysplastic syndrome or AML occurred in a small number of patients on the talazoparib arm (three MDS, one AML) versus one MDS case and no AML on the control arm, a difference worth discussing with patients starting this combination, particularly those with other risk factors for marrow dysfunction.

Cognitive Effects: A Practical Distinction Between ARPIs

Beyond efficacy, the choice between ARPIs increasingly involves quality-of-life considerations, particularly cognitive effects. A randomized phase 2 trial comparing enzalutamide and darolutamide using CANTAB-based objective cognitive testing over 24 weeks found significantly greater cognitive decline with enzalutamide, consistent with darolutamide's comparatively limited blood-brain barrier penetration. Notably, patients were permitted to cross over between arms, and while crossover eligibility was similar in both directions, every crossover that occurred moved from enzalutamide to darolutamide, none moved the other way, reinforcing the clinical signal beyond the objective testing data alone. This distinction is worth factoring into ARPI selection for patients with baseline cognitive vulnerability or strong concerns about preserving executive function, working memory, or visual memory during prolonged treatment.

Treatment De-Escalation: Who Can Safely Stop ADT and ARPI

For metastatic castration-sensitive patients responding exceptionally well to ADT plus ARPI therapy, a phase 2 trial evaluating treatment interruption found that patients achieving a PSA below 0.2 after at least a year of ARPI with ADT could safely discontinue both ADT and the ARPI, with resumption triggered by PSA rising above 5 or radiographic progression. In this trial, roughly 40% of patients remained off both ADT and ARPI at 18 months. This approach reflects a broader, evolving evidence base for treatment de-escalation in appropriately selected patients who achieve deep PSA responses, allowing meaningful treatment holidays without compromising disease control in this specific population. In practice, low-volume disease and a sustained deep PSA response over roughly two years are reasonable criteria to consider before initiating a treatment pause, always with close PSA monitoring in place to catch early signs of regrowth.

For Patients

Prostate cancer treatment is evolving quickly, and several recent studies are changing how doctors approach both early, localized disease and more advanced disease. For patients with high-risk prostate cancer having surgery to remove the prostate, adding a medication called apalutamide before and after surgery, on top of standard hormone therapy, meaningfully increased the chances of the cancer being eliminated at surgery and reduced the risk of it spreading later.

For prostate cancer that has already spread and carries certain inherited or tumor-specific genetic changes (HRR mutations), a PARP inhibitor combined with standard hormone therapy showed benefit across a wider range of these changes than previously known, including one called ATM that hadn't clearly benefited before. Genetic testing of the tumor can help identify good candidates.

For patients on long-term hormone therapy, cognitive side effects, including memory and concentration changes, are a real concern, and research shows some hormone medications affect thinking less than others. Finally, for patients who respond exceptionally well to treatment, with very low PSA sustained over time, new research supports that carefully monitored treatment breaks may be possible without compromising cancer control. Anyone on long-term hormone therapy should discuss these evolving options directly with their oncologist.

Key Takeaways

  • PROTEUS showed perioperative apalutamide plus ADT increased pathologic complete response rates (9% vs. 1%) and reduced metastasis risk by 20% in high-risk localized prostate cancer undergoing radical prostatectomy.

  • TALAPRO-3 demonstrated a 52% reduction in risk of progression or death with talazoparib plus enzalutamide in HRR-altered metastatic castration-sensitive prostate cancer, with the first clear benefit shown in ATM-altered disease specifically.

  • PARP inhibitor combinations carry meaningful hematologic toxicity, including a small but real risk of MDS/AML, warranting monitoring and patient counseling.

  • A head-to-head phase 2 trial found significantly greater objective cognitive decline with enzalutamide compared to darolutamide, a factor worth weighing in ARPI selection for cognitively vulnerable patients.

  • In appropriately selected patients achieving a deep PSA response (below 0.2) on ADT plus ARPI, roughly 40% remained treatment-free at 18 months after a supervised treatment interruption in phase 2 data.

References

  1. Taplin ME, et al. Perioperative Apalutamide plus ADT versus Placebo plus ADT with Radical Prostatectomy in High-Risk Localized or Locally Advanced Prostate Cancer: Final Analysis of the Phase 3 PROTEUS Study. American Society of Clinical Oncology Plenary Session, 2026; New England Journal of Medicine, 2026.

  2. Agarwal N, et al. TALAPRO-3: Talazoparib plus Enzalutamide versus Placebo plus Enzalutamide in Patients with HRR Gene-Altered Metastatic Castration-Sensitive Prostate Cancer. New England Journal of Medicine, 2026.

  3. Morgans A, et al. ARACOG (AFT-47): A Randomized Phase 2 Trial of Cognitive Effects of Darolutamide versus Enzalutamide in Advanced Prostate Cancer. American Society of Clinical Oncology, 2026.

  4. A-DREAM (Alliance A032101): A Phase 2 Trial of ADT and ARPI Interruption in Patients Responding Exceptionally to Androgen Receptor Pathway Inhibitor Therapy in Metastatic Hormone-Sensitive Prostate Cancer. American Society of Clinical Oncology, 2026.