Results
Among patients with BRCA-like disease, there was a significant improvement in PFS and a trend toward improved OS when veliparib was added to cisplatin. The median PFS was 5.9 months with veliparib and 4.2 months with placebo (P = .006). The median OS was 14.0 months and 12.1 months, respectively (P = .067).
Among patients with previously untreated BRCA-like disease, there were significant improvements in both PFS and OS.
The median PFS in this group was 6.1 months with veliparib and 4.2 months with placebo (P = .008). The 12-month PFS rates were 23% and 3%, respectively.
The median OS in this group was 17.8 months with veliparib and 10.3 months with placebo (P = .048). The 24-month OS rates were 43% and 20%, respectively.
There were no survival benefits with veliparib among patients with unclassified disease, non-BRCA-like disease, or BRCA-associated disease.
Dr. Sharma noted that the lack of significant improvement in the BRCA-associated group was likely due to the small sample size. “FDA approval of PARP inhibitors for treatment of germline BRCA-associated metastatic breast cancer during the course of this trial impacted accrual to this group,” she said.
Veliparib was associated with a higher rate of grade 3-4 hematologic toxicities, including neutropenia (46% vs. 19%), leukopenia (27% vs. 7%), anemia (23% vs. 7%), and thrombocytopenia (19% vs. 3%).
Dr. Sharma said results from this trial should prompt further research. “The combination of veliparib plus cisplatin warrants further evaluation in larger randomized trials for patients with BRCA-like phenotype TNBC,” she said.
Invited discussant Catherine M. Kelly, MB BCh, of Mater Misericordiae University Hospital in Dublin, called the trial “an ambitious study” that has created a “valuable tissue bank” for future translational research. She agreed that more work is necessary.
“Further research is needed to identify the optimal homologous recombination deficiency biomarkers critical in the early treatment-naive and in the advanced treatment-exposed disease settings,” Dr. Kelly said.
SWOG S1416 was funded by the National Institutes of Health and AbbVie. Dr. Sharma disclosed relationships with AstraZeneca, Merck, Novartis, and other companies. Dr. Kelly reported affiliations with Pfizer, Novartis, Roche, and MSD Oncology.
SOURCE: Sharma et al. ASCO 2020, Abstract 1001.