TUESDAY, Aug. 25, 2026 (HealthDay News) -- For patients with hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer (MBC), the combination of anastrozole, palbociclib, trastuzumab, and pertuzumab shows promise, according to a study published online July 30 in the Journal of the National Cancer Institute.
Rima Patel, M.D., from the Icahn School of Medicine at Mount Sinai in New York City, and colleagues evaluated frontline anastrozole, palbociclib, trastuzumab, and pertuzumab in patients with HR-positive, HER2-positive MBC. Patients received escalating doses of palbociclib with trastuzumab, pertuzumab, and anastrozole in phase 1, with a primary end point of maximum tolerated dose (MTD). In phase 2, all patients received palbociclib at the MTD, plus anastrozole, trastuzumab, and pertuzumab; the primary end point was clinical benefit rate (CBR) in the first six months.
The researchers found no dose-limiting toxicities at the 100- or 125-mg dose levels (three and six patients, respectively); the MTD was established as 125 mg. Phase 2 enrolled an additional 23 patients, yielding a response-evaluable population of 29 patients. The primary end point was 97 percent for CBR. Median progression-free survival was 24.9 months at a median follow-up of 45.3 months. At follow-up of 39.4 months, median overall survival was not reached. Neutropenia, leukopenia, diarrhea, and anemia were the most common treatment-related adverse events (TRAEs); 62 percent of patients had grade 3 TRAEs, most of which were hematologic.
"Although these findings need to be confirmed in larger randomized clinical trials, they suggest that some patients may eventually have an effective alternative to chemotherapy as their first treatment," coauthor Amy Tiersten, M.D., also from the Icahn School of Medicine at Mount Sinai, said in a statement.
Pfizer provided palbociclib and funding for the clinical trial.
