Docetaxel and PARPi additions to ARPI and ADT improve progression-free survival in mHSPCNew data shows potential benefits for advanced prostate cancer patients

This network meta-analysis evaluated the efficacy and safety of first-line systemic combination therapies for patients with metastatic hormone-sensitive prostate cancer (mHSPC). The analysis included a large total population of 18,689 patients to compare various triplet regimens against the standard of care, which consists of an androgen receptor pathway inhibitor (ARPI) combined with androgen deprivation therapy (ADT). The specific regimens evaluated included the addition of docetaxel or a polymerase inhibitor (PARPi) to the ARPI and ADT backbone.

The primary outcome measured was progression-free survival (PFS). For the triplet regimen consisting of docetaxel plus ARPI plus ADT compared to the doublet of ARPI plus ADT, the study reported a hazard ratio (HR) of 0.66 (95% CI 0.43-1.01). For the triplet regimen consisting of PARPi plus ARPI plus ADT compared to ARPI plus ADT, the study reported an HR of 0.55 (95% CI 0.23-1.34). While both triplet regimens showed a numerical improvement in progression-free survival, the results for both were not statistically significant in the all-comer population.

Secondary outcomes included overall survival (OS) and safety metrics. Regarding overall survival, the study identified a significant benefit for the docetaxel plus ARPI plus ADT triplet in a specific subgroup. In patients with high-volume disease, the docetaxel plus ARPi plus ADT regimen showed an HR of 0.76 (95% CI 0.61-0.95). However, no triplet regimen demonstrated a statistically significant OS benefit over ARPI plus ADT in the all-comer population.

Safety and tolerability were also assessed. The study found that adding docetaxel or PARPi did not result in a statistically significant increase in the risk of severe adverse events. However, the researchers noted that these safety estimates were characterized by substantial imprecision.

These findings provide a nuanced view of triplet intensification in mHSPC. While the results for docetaxel and PARPi additions to the ARPI and ADT backbone show potential for improved progression-free survival, the lack of statistical significance in the all-comer population and the high level of imprecision for PARPi-based regimens suggest caution. The significant OS benefit in the high-volume subgroup suggests that triplet intensification may be most clinically relevant for specific patient phenotypes.

Several methodological limitations were identified in the study. These included the risk of bias from open-label designs, clinical inconsistency in prior docetaxel exposure across the comparator arms, and significant imprecision for PARPi-based regimens due to small sample sizes in the underlying phase II data. The certainty of evidence varies by outcome: the evidence for docetaxel plus ARPI plus ADT for PFS is moderate, while the evidence for PARPi plus ARPI plus ADT for PFS is low. The evidence for docetaxel plus ARPI plus ADT for OS in the high-volume subgroup is high.

Clinically, these results suggest that while triplet intensification may improve progression-free survival, the overall survival benefits appear limited to specific subgroups, such as those with high-volume disease. This suggests a need for a more selective, biomarker-driven, or targeted approach in practice. Questions remain regarding the long-term durability of these outcomes and the specific factors that define the high-volume subgroup to optimize patient selection for triplet therapies.