PARP-inhibitors Improve Progression-Free Survival in Breast Cancer Patients with Previous Platinum Exposure – A Systematic Review and Meta-Analysis

Abstract Importance: The poly-adenosine diphosphate–ribose polymerase (PARP) enzymes are important for DNA single-strand break repair and PARP inhibitors (PARPi) cause an accumulation of unresolved DNA damage in tumors with BRCA1/2 mutations, resulting in cell death. However, because platinum salts also ultimately cause double-strand DNA breaks and may have overlapping mechanisms of resistance with PARPi, the efficacy of PARPi in patients with prior platinum therapy is unknown. Objective We sought to evaluate the efficacy of PARPi in patients with BRCA1/2-related breast cancer and previous platinum exposure. Data Sources: PubMed, Embase, and Cochrane Central Register of Controlled Trials databases were searched for papers up to June 26, 2022. Study Selection: We performed a systematic review and meta-analysis of studies that evaluated the efficacy of PARPi in patients with advanced or metastatic breast cancer and germline BRCA1/2 mutations. Two independent investigators identified double-blind, randomized controlled trials (RCTs) that included the subgroup of previous exposure to platinum. Data Extraction and Synthesis: Data extraction from published reports and quality assessment were performed under Cochrane recommendations. The software Review Manager 5.3 was selected for conducting the statistical analyses. Main Outcome(s) and Measure(s): The primary endpoint of interest was progression-free survival (PFS). Hazard ratios (HRs) with a 95% confidence interval (CI) were pooled, and a p-value of < 0.05 was considered statistically significant. Results From 2,069 database results (487 on PubMed; 1,376 on Embase; and 206 on Cochrane), 42 studies were fully reviewed, and 4 RCTs (total of 249 patients) were included in the final investigation. The PARPi included were Olaparib, Talazoparib, Niraparib, and Veliparib. Pooled analysis showed that PARPi improved PFS in breast cancer patients with prior treatment with platinum-based therapy compared to the control group [HR = 0.72; 95% CI, 0.53–0.97; p = 0.03]. For comparison, the population without previous platinum exposure had a similar magnitude of benefit from PARPi [HR = 0.68; 95% CI, 0.52–0.89; p = 0.005]. Conclusions and Relevance: Despite the concerns about cross-resistance between PARPi and platinum agents, patients with advanced breast cancer and previous exposure to platinum therapy have a longer PFS with PARPi when compared to standard chemotherapy.