Brain Radiotherapy With Pyrotinib and Capecitabine in Patients With ERBB2-Positive Advanced Breast Cancer and Brain MetastasesA Nonrandomized Phase 2 Trial

IMPORTANCE The potential benefit of combining intracranial effective systemic therapy with radiotherapy for patients with breast cancer with brain metastases remains unclear.OBJECTIVE To assess the activity and safety of combining radiotherapy with pyrotinib and capecitabine in patients with ERBB2-positive breast cancer and brain metastases.DESIGN, SETTING, AND PARTICIPANTS This was a single-arm, single-center, phase 2 nonrandomized clinical trial with a safety run-in phase. Between January 2020 and August 2022, patients with ERBB2-positive breast cancer and brain metastases were enrolled. The data cutoff date was February 1, 2023. INTERVENTIONS Patients received either fractionated stereotactic radiotherapy or whole-brain radiotherapy. Treatment with pyrotinib (400 mg, once daily) and capecitabine (1000 mg/m(2), twice daily, on days 1-14 of each 21-day cycle) was initiated from the first day of radiotherapy to the seventh day after the completion of radiotherapy and continued until disease progression or unacceptable toxic effects.MAIN OUTCOMES AND MEASURES The primary end point was 1-year central nervous system (CNS) progression-free survival (PFS) rate. Secondary end points included CNS objective response rate (ORR), PFS, overall survival (OS), safety, and changes in neurocognitive function.RESULTS A total of 40 female patients (median age, 50.5 years [IQR, 46-59 years]) were enrolled and received treatment, including 3 patients in safety run-in phase. With a median follow-up of 17.3 months (IQR, 10.3-26.9), the 1-year CNS PFS rate was 74.9% (95% CI, 61.9%-90.7%), and the median CNS PFS was 18.0 months (95% CI, 15.5 to not reached). The 1-year PFS rate was 66.9% (95% CI, 53.1%-84.2%), and the median PFS was 17.6 months (95% CI, 12.8-34.1). The CNS objective response rate was 85% (34 of 40). Median overall survival was not reached. The most common grade 3 or 4 treatment-related adverse event was diarrhea (7.5%). Asymptomatic radiation necrosis was identified in 4 of 67 lesions (6.0%) treated with fractionated stereotactic radiotherapy. Most patients maintained neurocognitive function, as evaluated by the Mini-Mental State Examination at different points.CONCLUSIONS AND RELEVANCE The results of this trial suggest that radiotherapy combined with pyrotinib and capecitabine is associated with long intracranial survival benefit in patients with ERBB2-positive advanced breast cancer and brain metastases with an acceptable safety profile. This combination deserves further validation.