In prostate cancer, the benefit of PARP inhibitors is overwhelmingly driven by BRCA2 mutations, which are more common than BRCA1. While PALB2 also shows a strong response, genes like BRCA1 offer only modest benefit, and ATM mutations show almost no response. This highlights the need for a gene-specific, not class-specific, approach to treatment.

Early data shows that combining PARP inhibitors with radioligand therapy like lutetium-PSMA is surprisingly safe, unlike toxic combinations with chemotherapy. This promising strategy may potentiate the DNA-damaging effect of the beta-emitting radiopharmaceutical, potentially extending its benefit to a broader patient population beyond those with HR-deficient tumors.

After years of successfully intensifying hormonal therapy, the focus in prostate cancer is shifting toward de-intensification. Researchers are exploring intermittent therapy for top responders and developing non-hormonal approaches like radioligands to spare patients the chronic, life-altering side effects of permanent castration.

Patients with BRCA-mutated prostate cancer who progress on first-line PARP inhibitors have very poor options. Standard therapies like docetaxel are largely ineffective, and emerging data suggests cross-resistance with Lutetium, creating a significant unmet clinical need for novel approaches.

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.

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.

For a newly diagnosed metastatic prostate cancer patient, an effective strategy is to initiate ADT alone while immediately ordering NGS testing. Waiting a few weeks for the genetic results before adding an ARPI allows for a more informed treatment choice, such as selecting a PARP inhibitor combination for a patient with a BRCA2 mutation.

For biochemically recurrent (BCR) prostate cancer, which is often indolent, trials should not wait years to study treatment reduction. The NCI group universally agreed that de-escalation strategies—such as intermittent therapy—should be the default design from the outset, prioritizing quality of life and avoiding overtreatment.

A unique three-arm trial allowing crossover between single-agent PARP inhibitors, AR inhibitors, and a combination showed superior outcomes for the upfront combination. This suggests that "saving" a therapy for later is a suboptimal strategy for this biomarker-selected patient population.