Combination of paclitaxel and two schedules of gefitinib in patients with metastatic breast cancer

Abstract

10599 Background: The epidermal growth factor receptor (EGFR) may be overexpressed in breast cancer. Inhibition of EGFR signaling by gefitinib (Iressa) enhances the in vitro antitumor activity of many cytotoxic drugs including paclitaxel. Methods: In this phase II study patients (pts) with measurable metastatic breast cancer and maximum prior exposure to two chemotherapies were randomized to paclitaxel (100 mg/m2 on days 1, 8 q21) and continuous gefitinib, 250 mg daily for 21 days (arm A); or paclitaxel (100 mg/m2 on days 8, 15 q21) with gefitinib 250 mg daily from day 1 to 15 (arm B). Therapy continued for at least 4 cycles after best response. After 6 cycles, responding pts continued with gefitinib monotherapy until progression or unacceptable toxicity. Results: 16 pts in arm A and 17 in arm B were enrolled; 25 had visceral disease (12 in arm A and 13 in arm B). Median age was 53 years (range 29–70). All but one pt received prior anthracyclines and 9 also prior taxanes. Overall 17 pts responded to therapy (intent to treat analysis; arm A: 62.5%, 95% CI: 35.4–84.8%; arm B: 41.2%, 95% CI: 18.4–67.1%). Disease control (CR+PR+SD) was achieved in 81.3% of pts in arm A and 76.5% in arm B, with 10 and 6 pts who continued with gefitinib monotherapy after completing the combination schedule. Median time to progression was 250 (arm A) and 204 days (arm B), while median response duration was 212 (arm A) and 285 days (arm B). Tolerability was good with either schedule of gefitinib. Diarrhea was frequent (68.8% and 64.7%) and of grade 3–4 severity in 6% of pts in arm A and in arm B. Grade 3–4 neutropenia affected 6% and 12% of pts respectively, and 6% of pts in both arms had a grade 3–4 increase of AST and ALT. Other grade 1–2 adverse events included acneiform rash (100% in arm A and 58.8% in arm B), sensory neuropathy (68.8% and 58.8%), anemia (50.0% and 52.9%), neutropenia (25.0% and 17.6%) and myalgia (37.5% and 41.2%). Conclusions: The combination of paclitaxel with gefitinib given continuously or for 2 out of every 3 weeks is feasible and well tolerated. The discontinuous schedule caused less skin toxicity. The good antitumor activity deserves further studies to identify sensitive subgroups and mechanisms of sensitivity. IRESSA is a trademark of the AstraZeneca group of companies. [Table: see text]