Pyrotinib after trastuzumab-based adjuvant therapy in patients with HER2-positive breast cancer (PERSIST): A multicenter phase II trial

Background: Approximately one-third of patients with HER2-positive breast cancer experienced recurrence within 10 years after receiving 1 year of adjuvant trastuzumab. The ExteNET study showed that 1 year of extended adjuvant neratinib after trastuzumab-based adjuvant therapy could reduce invasive disease-free survival (iDFS) events compared with placebo. This study investigated the efficacy and safety of pyrotinib, an irreversible pan-HER receptor tyrosine kinase inhibitor, after trastuzumab-based adjuvant therapy in patients with high-risk, HER2-positive early or locally advanced breast cancer. Methods: This multicenter phase II trial was conducted at 23 centers in China. After enrollment, patients received 1 year of extended adjuvant pyrotinib (400 mg/day), which should be initiated within 6 months after the completion of 1-year adjuvant therapy (trastuzumab alone or plus pertuzumab). The primary endpoint was 2-year iDFS rate. Results: Between January 2019 and February 2022, 141 eligible women were enrolled and treated. As of October 10, 2022, the median follow-up was 24 (interquartile range, 18.0-34.0) months. The 2-year iDFS rate was 94.59% (95% confidence interval [CI]: 88.97-97.38) in all patients, 94.90% (95% CI: 86.97-98.06) in patients who completed 1-year treatment, 90.32% (95% CI: 72.93-96.77) in patients who completed only 6-month treatment, 96.74% (95% CI: 87.57-99.18) in the hormone receptor (HR)-positive subgroup, 92.77% (95% CI: 83.48-96.93) in the HR-negative subgroup, 96.88% (95% CI: 79.82-99.55) in the lymph node-negative subgroup, 93.85% (95% CI: 86.81-97.20) in the lymph node-positive subgroup, 97.30% (95% CI: 82.32-99.61) in patients with adjuvant trastuzumab plus pertuzumab, and 93.48% (95% CI: 86.06-97.02) in patients with adjuvant trastuzumab. The most common adverse events were diarrhea (79.4%), fatigue (36.9%), lymphocyte count decreased (36.9%), nausea (33.3%), and hand-foot syndrome (33.3%). Conclusions: Extended adjuvant pyrotinib administrated after trastuzumab-based adjuvant therapy showed promising efficacy in patients with high-risk HER2-positive breast cancer. The follow-up is ongoing to determine the long-term benefit. Funding: No external funding was received for this work. Clinical trial number: ClinicalTrials.gov: NCT05880927