This is a phase II, multicenter, double-blind, randomized, placebo-controlled trial. Patients will be randomized in a double-blind manner in a 1:1 ratio to receive either 250 mg/day ZD1839 or matched placebo in combination with 1 mg/day anastrozole. The dose of ZD1839 has been selected based on clinical studies in other tumor types suggesting identical efficacy together with a better toxicity profile in patients treated at 250 mg compared to 500 mg/day. The 1 mg dose of anastrozole is the standard approved dose.