Chemotherapy-free regimen induces ‘high’ clinical benefit rate in metastatic breast cancer
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Key takeaways:
- The combination conferred a clinical benefit rate of 97%.
- Nearly three-quarters of patients achieved objective response.
SAN ANTONIO — A four-therapy combination conferred clinical benefit to nearly all evaluable patients with metastatic triple-positive breast cancer, according to findings of the ASPIRE trial presented at San Antonio Breast Cancer Symposium.
The combination of anastrozole, palbociclib (Ibrance, Pfizer), trastuzumab and pertuzumab (Perjeta, Genentech) provides a chemotherapy-free alternative for patients with previously untreated triple-positive metastatic disease, according to researchers.
“I’m very happy about the 97% clinical benefit rate. I was happily surprised that it was so high,” Amy Tiersten, MD, professor in the division of hematology and medical oncology and a member of the breast cancer medical oncology program at Mount Sinai's Icahn School of Medicine, told Healio.
Background and methodology
Standard front-line treatment for patients with hormone receptor-positive, HER2-positive metastatic breast cancer includes cytotoxic chemotherapy and HER2-targeting antibodies, such as trastuzumab and pertuzumab (Perjeta, Genentech).
Researchers theorized that the combination of dual antibodies with antiestrogen therapy and a cyclin-dependent kinase 4/6 inhibitor could provide a potentially novel, all biologic, chemotherapy-free treatment for untreated patients with hormone receptor-positive, HER2-positive metastatic breast cancer.
In phase 1, researchers enrolled nine patients who received escalating doses of palbociclib in conjunction with trastuzumab, pertuzumab and the aromatase inhibitor anastrozole. Three patients received 100 mg palbociclib and six received 125 mg.
Researchers observed no dose-limiting toxicities in either cohort in phase 1, which established 125 mg as the maximum tolerated dose.
In phase 2, researchers enrolled an additional 24 patients who received 125 mg palbociclib — the maximum tolerated dose observed in phase 1 — along with anastrozole, trastuzumab and pertuzumab.
Results
The intention-to-treat analysis included all 30 patients (median age, 57.6 years; 72.4% white; 20.7% premenopausal) from both phases who received 125 mg palbociclib.
Researchers reported a clinical benefit rate of 97% (95% CI, 0.83-1) and objective response rate of 73% (95% CI, 54-88).
Median time to response was 2.8 months (95% CI, 2.7-5.2) and median duration of response was 37.8 months.
Safety results appeared consistent with known toxicity profiles of each agent. The most common adverse events included neutropenia (87%), diarrhea (83%), leukopenia (77%), anemia (70%) and fatigue (60%).
The most common grade 3 to grade 4 events included neutropenia (46%, leukopenia (23%), anemia (17%) and diarrhea (10%).
Collapse
Tiersten A, et al. Abstract RF02-01. Presented at: San Antonio Breast Cancer Symposium; Dec. 5-9, 2023, San Antonio.
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