While BRCA2 mutations are typically associated with aggressive prostate cancer, this is not universal. Clinical experience reveals a subset of BRCA2 patients with surprisingly indolent disease, even without PARP inhibitors. This suggests other clinical or molecular factors are at play, challenging a one-size-fits-all treatment approach.

The modest benefit of PARP inhibitors in metastatic breast cancer, compared to ovarian cancer, is likely due to resistance induced by prior exposure to DNA-damaging agents like anthracyclines. This explains the clinical rationale for moving PARP inhibitors to earlier treatment settings, such as neoadjuvant or adjuvant therapy, before resistance develops.

When a patient has a BRCA2 mutation, clinicians on the panel view it as such a dominant predictive biomarker that they would prioritize a PARP inhibitor-based triplet regimen. This single genetic finding often outweighs other clinical factors or even the potential addition of docetaxel in treatment decisions.

The FDA is predicted to approve new PARP inhibitors from trials like AMPLITUDE only for BRCA-mutated patients, restricting use to where data is strongest. This contrasts with the EMA's potential for broader approvals or denials. This highlights the diverging regulatory philosophies that create different drug access landscapes in the US and Europe.

For high-risk, HR+ patients with germline BRCA mutations, data suggest they derive less benefit from CDK4/6 inhibitors. A practical approach is to give one year of the PARP inhibitor olaparib first, followed by a CDK4/6 inhibitor, capitalizing on the delayed initiation allowance in major trials.

The BRCA-Way trial showed a combination of abiraterone and olaparib was effective. However, its relevance is limited as many patients now receive abiraterone upfront. The next-generation TALENT trial is designed specifically to address this, testing if re-challenging with an AR-pathway inhibitor alongside a PARP inhibitor is beneficial, demonstrating how trial design must constantly evolve to answer questions raised by new standards of care.

A nuanced approach to PARP inhibitors involves reserving combinations for BRCA2 patients with clear, aggressive clinical features like high-volume disease or liver metastases. This strategy balances potent efficacy against toxicity for a molecularly defined but clinically heterogeneous group, avoiding overtreatment of those with more indolent disease.

Three 2025 trials (AMPLITUDE, PSMA-addition, CAPItello) introduced personalized therapy for metastatic hormone-sensitive prostate cancer. However, significant benefits were confined to narrow subgroups, like BRCA-mutated patients. This suggests future success depends on even more stringent patient selection, not broader application of targeted agents.

The initial broad enthusiasm for PARP inhibitors in ovarian cancer has been refined. New data confirms a lack of overall survival improvement for patients with HRD-negative (or HR proficient) tumors, pushing clinicians toward a precision medicine approach where these drugs are reserved for patients with BRCA mutations or HRD-positive disease who are most likely to benefit.