Patients undergo surgical ovarian suppression (OS) or medical OS with luteinizing hormone-releasing hormone (LHRH) agonist (i.e., goserelin or leuprolide acetate, intramuscularly once monthly for 3 months and then every 2 months thereafter for the duration of study therapy). Beginning on day 14 after initiation of LHRH-agonist therapy or surgery, patients receive oral letrozole once daily. Treatment continues in the absence of disease progression or unacceptable toxicity.