Background: Acquired and de novo endocrine resistance in breast cancer (BC) may be associated with overexpression of epidermal growth factor receptor (EGFR). Gefinitib is an orally active selective EGFR inhibitor which might benefit advanced breast cancer (ABC) patients either with acquired hormone resistance or with hormone receptor (HR)-negative tumors.
Patients and methods: A two-arm multicenter phase II trial of oral gefitinib 500 mg/day was planned in two groups of 45 patients with ABC for whom chemotherapy was not currently indicated. Group 1 had hormone-resistant BC defined as HR-positive BC with progression after treatment with tamoxifen and an aromatase inhibitor. Group 2 had HR-negative BC. Tumor response was assessed every 8 weeks. The primary end point was the clinical benefit rate (CBR).
Results: Forty patients with hormone-resistant BC had a CBR of 0%. Two of 25 HR-negative BC patients showed stable disease (less than a 50% reduction and less than a 25% increase in the sum of the products of two perpendicular diameters of all measured lesions and the appearance of no new lesions) at 24 weeks resulting in a CBR of 7.7% (95% CI 0.9% to 25.1%). Enrollment ceased due to the low CBR. Toxicity resulted in treatment interruption (46%), dose reduction (20%) and withdrawal (11%) of patients.
Conclusion: At a dose of 500 mg/day, gefitinib monotherapy resulted in a low CBR and no tumor response was identified.