Targeting BRCA and PALB2 in Pancreatic Cancer
1Abramson Cancer Center, 10th Floor Perelman Center South, The University of Pennsylvania, 3400 Civic Center Blvd, Philadelphia, PA, 19121, USA.
Opinion Statement:
An important subgroup of pancreatic ductal adenocarcinomas (PDACs) harbor pathogenic variants in BRCA1, BRCA2, or PALB2. These tumors are exquisitely sensitive to platinum-based chemotherapy and patients may experience deep and durable responses to this treatment. PARP inhibitors offer potential respite from the cumulative toxicities of chemotherapy as they significantly extend progression-free survival compared to a chemotherapy holiday. Given the lack of proven survival benefit, the decision to use a maintenance PARP inhibitor rather than continue chemotherapy should be individualized. Interestingly, in both published clinical trials of maintenance PARP inhibitors, there is a striking range of interpatient benefit: Even in the platinum-sensitive setting, roughly 25% of tumors appear to be PARP inhibitor refractory (progressive disease within 2 months of starting treatment), 50% sustain moderate benefit (up to 2 years), and 25% are hyper-responsive (more than 2 years of benefit). This finding highlights the need to refine our understanding of which patients will respond to maintenance PARP inhibitors, both by being able to identify biallelic loss and by deepening our knowledge of resistance mechanisms and who develops them. Recent data supports that reversion mutations are common in PARP inhibitor refractory patients, but we have little understanding of the mechanisms that drive delayed resistance and long-term responses. Identifying which patients are more prone to certain mechanisms of resistance and tackling them with specific treatment strategies are areas of active investigation. Additionally, given that PARP inhibitors have limited overall efficacy for most patients, upfront combination strategies are an important future strategy.
Insights
Pancreatic cancer patients with BRCA/PALB2 variants benefit from PARP inhibitors, but response varies. Understanding resistance mechanisms is key for personalized treatment and combination strategies.
Area of Science:
- Oncology
- Genetics
- Pharmacology
Background:
- Pancreatic ductal adenocarcinomas (PDACs) with BRCA1, BRCA2, or PALB2 pathogenic variants are sensitive to platinum chemotherapy.
- PARP inhibitors offer extended progression-free survival compared to chemotherapy cessation in these patients.
- Individualized treatment decisions are necessary due to a lack of proven survival benefit for maintenance PARP inhibitors over continued chemotherapy.
Purpose of the Study:
- To explore the variable patient responses to maintenance PARP inhibitors in platinum-sensitive PDAC.
- To highlight the need for better identification of patients who will respond to PARP inhibitors.
- To investigate mechanisms of resistance and potential combination strategies for improved efficacy.
Main Methods:
- Analysis of published clinical trial data for maintenance PARP inhibitors in PDAC.
- Review of emerging data on resistance mechanisms, including reversion mutations.
- Exploration of patient stratification based on genetic profiles and resistance patterns.
Main Results:
- Significant interpatient variability in PARP inhibitor response was observed: 25% refractory, 50% moderate benefit (up to 2 years), 25% hyper-responsive (>2 years).
- Reversion mutations are frequent in refractory cases, but mechanisms of delayed resistance and long-term response remain unclear.
- Current understanding necessitates further research into resistance mechanisms and predictive biomarkers.
Conclusions:
- Maintenance PARP inhibitors show promise but require personalized application due to variable efficacy.
- Identifying biallelic loss and understanding resistance mechanisms are crucial for optimizing PARP inhibitor therapy.
- Future strategies should focus on upfront combination therapies and targeted approaches to overcome resistance in PDAC.
