Conference Coverage

Expanding the role of PARP inhibitors in breast cancer


 

FROM ASCO 2020

For patients with BRCA-like triple-negative breast cancer (TNBC), adding veliparib to cisplatin chemotherapy may extend survival, based on results from the phase 3 SWOG S1416 trial.

All patients with BRCA-like TNBC had a significant improvement in progression-free survival (PFS) when they received veliparib plus cisplatin. Previously untreated patients with BRCA-like TNBC had a significant improvement in overall survival (OS) as well.

The results are a “very positive step towards expanding the role of PARP inhibitors beyond germline BRCA in breast cancer,” reported lead author Priyanka Sharma, MD, of the University of Kansas Medical Center in Kansas City, who presented the findings as part of the American Society of Clinical Oncology virtual scientific program.

According to Dr. Sharma, PARP inhibitors have demonstrated efficacy for certain patients with BRCA wild-type ovarian cancer, such as those with homologous recombination deficiency, which also occurs in approximately half of patients with BRCA wild-type TNBC. In TNBC, homologous recombination deficiency and other aberrations lead to a BRCA-like disease phenotype, which may respond to PARP inhibitors.

Dr. Sharma noted that previous attempts to use PARP inhibitors for BRCA wild-type TNBC have revealed obstacles, such as the inefficacy of PARP inhibitor monotherapy and dose-limiting myelosuppression when PARP inhibitors were added to chemotherapy. The issue of bone marrow toxicity may be mitigated by veliparib, which has minimal PARP-trapping activity, she explained.

“A phase 1 trial has demonstrated that adequate doses of cisplatin can be delivered safely in combination with the near-maximal single-agent dose of veliparib in patients with metastatic TNBC,” Dr. Sharma said.

She and her colleagues put this finding to the test in a phase 3 trial that enrolled 335 patients with metastatic and/or loco-regionally recurrent TNBC or BRCA-associated HER2-negative breast cancer. Patients could be previously untreated or have received one prior cytotoxic chemotherapy for metastatic disease.

Of the patients enrolled, 321 met eligibility criteria, 294 had germline BRCA testing, and 209 had BRCA-like assessment.

Patients were divided into the following groups: germline BRCA-associated disease (n = 37), BRCA-like disease (n = 99), non-BRCA-like disease (n = 110), and unclassified (n = 75).

In each group, patients were randomized in a 1:1 ratio to receive cisplatin (75 mg/m2on day 1) plus veliparib (300 mg twice daily on days 1-14) every 3 weeks, or cisplatin with placebo. The primary endpoint was PFS.

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