DISEASE CHARACTERISTICS:

• Histologically confirmed breast cancer

  • Metastatic disease

• Initial clinical benefit from tamoxifen for metastatic disease, defined by 1 of the following:

  • Stable disease for 24 weeks or longer
  • Objective tumor response
• Documentation of clinical progression on tamoxifen within the past 6 weeks

• Hormone receptor status:

  • Estrogen or progesterone receptor positive on most recently analyzed biopsy

PATIENT CHARACTERISTICS:

Age

• 18 and over

Sex

• Not specified

Menopausal status

• Not specified

Performance status

• ECOG 0-2

Life expectancy

• At least 6 months

Hematopoietic

• Absolute neutrophil count ≥ 1,500/mm^3
• Platelet count ≥ 100,000/mm^3

Hepatic

• AST ≤ 1.5 times upper limit of normal (ULN)
• Bilirubin ≤ 1.5 times ULN

Renal

• Creatinine ≤ 1.5 times ULN OR
• Creatinine clearance ≥ 50 mL/min

Pulmonary

• No clinically active interstitial lung disease

  • Patients with asymptomatic chronic stable radiographic changes are eligible

Other

• Not pregnant or nursing
• Fertile patients must use effective contraception
• No known hypersensitivity to gefitinib
• No other malignancy within the past 5 years except basal cell carcinoma or carcinoma in situ of the cervix

PRIOR CONCURRENT THERAPY:

Biologic therapy

• No concurrent trastuzumab (Herceptin®)

Chemotherapy

• No concurrent cytotoxic chemotherapy

Endocrine therapy

• See Disease Characteristics
• At least 2 weeks since other prior tamoxifen
• No concurrent hormone replacement therapy
• No other concurrent antiestrogens, including raloxifene
• No concurrent aromatase inhibitors
• No concurrent megestrol
• Concurrent systemic steroids for reasons other than skin toxicity allowed provided the steroids were initiated before study entry AND dose remains stable

Radiotherapy

• Concurrent palliative radiotherapy as short-term treatment for symptomatic bone metastases allowed provided other evaluable sites of disease are present AND treatment lasts no more than 14 days

Surgery

• Recovered from prior oncologic or other major surgery
• No concurrent surgery during and for 7 days after study treatment
• No concurrent ophthalmic surgery

Other

• Recovered from all prior therapy (except alopecia)
• More than 30 days since prior investigational drugs
• No other concurrent investigational agents

• No concurrent administration of any of the following:

  • Phenytoin
  • Carbamazepine
  • Barbiturates
  • Rifampin
  • Phenobarbital
  • Hypericum perforatum (St. John's wort)
  • Systemic retinoids
  • CYP3A4 inhibitors (e.g., itraconazole)
  • Drugs that cause significant sustained elevation in gastric pH ≥ 5